1This is ld.info, produced by makeinfo version 4.8 from ld.texinfo. 2 3INFO-DIR-SECTION Software development 4START-INFO-DIR-ENTRY 5* Ld: (ld). The GNU linker. 6END-INFO-DIR-ENTRY 7 8 This file documents the GNU linker LD (GNU Binutils) version 2.21.1. 9 10 Copyright (C) 1991, 1992, 1993, 1994, 1995, 1996, 1997, 1998, 1999, 112000, 2001, 2002, 2003, 2004, 2005, 2006, 2007, 2008, 2009 Free 12Software Foundation, Inc. 13 14 Permission is granted to copy, distribute and/or modify this document 15under the terms of the GNU Free Documentation License, Version 1.3 or 16any later version published by the Free Software Foundation; with no 17Invariant Sections, with no Front-Cover Texts, and with no Back-Cover 18Texts. A copy of the license is included in the section entitled "GNU 19Free Documentation License". 20 21 22File: ld.info, Node: Top, Next: Overview, Up: (dir) 23 24LD 25** 26 27This file documents the GNU linker ld (GNU Binutils) version 2.21.1. 28 29 This document is distributed under the terms of the GNU Free 30Documentation License version 1.3. A copy of the license is included 31in the section entitled "GNU Free Documentation License". 32 33* Menu: 34 35* Overview:: Overview 36* Invocation:: Invocation 37* Scripts:: Linker Scripts 38 39* Machine Dependent:: Machine Dependent Features 40 41* BFD:: BFD 42 43* Reporting Bugs:: Reporting Bugs 44* MRI:: MRI Compatible Script Files 45* GNU Free Documentation License:: GNU Free Documentation License 46* LD Index:: LD Index 47 48 49File: ld.info, Node: Overview, Next: Invocation, Prev: Top, Up: Top 50 511 Overview 52********** 53 54`ld' combines a number of object and archive files, relocates their 55data and ties up symbol references. Usually the last step in compiling 56a program is to run `ld'. 57 58 `ld' accepts Linker Command Language files written in a superset of 59AT&T's Link Editor Command Language syntax, to provide explicit and 60total control over the linking process. 61 62 This version of `ld' uses the general purpose BFD libraries to 63operate on object files. This allows `ld' to read, combine, and write 64object files in many different formats--for example, COFF or `a.out'. 65Different formats may be linked together to produce any available kind 66of object file. *Note BFD::, for more information. 67 68 Aside from its flexibility, the GNU linker is more helpful than other 69linkers in providing diagnostic information. Many linkers abandon 70execution immediately upon encountering an error; whenever possible, 71`ld' continues executing, allowing you to identify other errors (or, in 72some cases, to get an output file in spite of the error). 73 74 75File: ld.info, Node: Invocation, Next: Scripts, Prev: Overview, Up: Top 76 772 Invocation 78************ 79 80The GNU linker `ld' is meant to cover a broad range of situations, and 81to be as compatible as possible with other linkers. As a result, you 82have many choices to control its behavior. 83 84* Menu: 85 86* Options:: Command Line Options 87* Environment:: Environment Variables 88 89 90File: ld.info, Node: Options, Next: Environment, Up: Invocation 91 922.1 Command Line Options 93======================== 94 95 The linker supports a plethora of command-line options, but in actual 96practice few of them are used in any particular context. For instance, 97a frequent use of `ld' is to link standard Unix object files on a 98standard, supported Unix system. On such a system, to link a file 99`hello.o': 100 101 ld -o OUTPUT /lib/crt0.o hello.o -lc 102 103 This tells `ld' to produce a file called OUTPUT as the result of 104linking the file `/lib/crt0.o' with `hello.o' and the library `libc.a', 105which will come from the standard search directories. (See the 106discussion of the `-l' option below.) 107 108 Some of the command-line options to `ld' may be specified at any 109point in the command line. However, options which refer to files, such 110as `-l' or `-T', cause the file to be read at the point at which the 111option appears in the command line, relative to the object files and 112other file options. Repeating non-file options with a different 113argument will either have no further effect, or override prior 114occurrences (those further to the left on the command line) of that 115option. Options which may be meaningfully specified more than once are 116noted in the descriptions below. 117 118 Non-option arguments are object files or archives which are to be 119linked together. They may follow, precede, or be mixed in with 120command-line options, except that an object file argument may not be 121placed between an option and its argument. 122 123 Usually the linker is invoked with at least one object file, but you 124can specify other forms of binary input files using `-l', `-R', and the 125script command language. If _no_ binary input files at all are 126specified, the linker does not produce any output, and issues the 127message `No input files'. 128 129 If the linker cannot recognize the format of an object file, it will 130assume that it is a linker script. A script specified in this way 131augments the main linker script used for the link (either the default 132linker script or the one specified by using `-T'). This feature 133permits the linker to link against a file which appears to be an object 134or an archive, but actually merely defines some symbol values, or uses 135`INPUT' or `GROUP' to load other objects. Specifying a script in this 136way merely augments the main linker script, with the extra commands 137placed after the main script; use the `-T' option to replace the 138default linker script entirely, but note the effect of the `INSERT' 139command. *Note Scripts::. 140 141 For options whose names are a single letter, option arguments must 142either follow the option letter without intervening whitespace, or be 143given as separate arguments immediately following the option that 144requires them. 145 146 For options whose names are multiple letters, either one dash or two 147can precede the option name; for example, `-trace-symbol' and 148`--trace-symbol' are equivalent. Note--there is one exception to this 149rule. Multiple letter options that start with a lower case 'o' can 150only be preceded by two dashes. This is to reduce confusion with the 151`-o' option. So for example `-omagic' sets the output file name to 152`magic' whereas `--omagic' sets the NMAGIC flag on the output. 153 154 Arguments to multiple-letter options must either be separated from 155the option name by an equals sign, or be given as separate arguments 156immediately following the option that requires them. For example, 157`--trace-symbol foo' and `--trace-symbol=foo' are equivalent. Unique 158abbreviations of the names of multiple-letter options are accepted. 159 160 Note--if the linker is being invoked indirectly, via a compiler 161driver (e.g. `gcc') then all the linker command line options should be 162prefixed by `-Wl,' (or whatever is appropriate for the particular 163compiler driver) like this: 164 165 gcc -Wl,--start-group foo.o bar.o -Wl,--end-group 166 167 This is important, because otherwise the compiler driver program may 168silently drop the linker options, resulting in a bad link. Confusion 169may also arise when passing options that require values through a 170driver, as the use of a space between option and argument acts as a 171separator, and causes the driver to pass only the option to the linker 172and the argument to the compiler. In this case, it is simplest to use 173the joined forms of both single- and multiple-letter options, such as: 174 175 gcc foo.o bar.o -Wl,-eENTRY -Wl,-Map=a.map 176 177 Here is a table of the generic command line switches accepted by the 178GNU linker: 179 180`@FILE' 181 Read command-line options from FILE. The options read are 182 inserted in place of the original @FILE option. If FILE does not 183 exist, or cannot be read, then the option will be treated 184 literally, and not removed. 185 186 Options in FILE are separated by whitespace. A whitespace 187 character may be included in an option by surrounding the entire 188 option in either single or double quotes. Any character 189 (including a backslash) may be included by prefixing the character 190 to be included with a backslash. The FILE may itself contain 191 additional @FILE options; any such options will be processed 192 recursively. 193 194`-a KEYWORD' 195 This option is supported for HP/UX compatibility. The KEYWORD 196 argument must be one of the strings `archive', `shared', or 197 `default'. `-aarchive' is functionally equivalent to `-Bstatic', 198 and the other two keywords are functionally equivalent to 199 `-Bdynamic'. This option may be used any number of times. 200 201`--audit AUDITLIB' 202 Adds AUDITLIB to the `DT_AUDIT' entry of the dynamic section. 203 AUDITLIB is not checked for existence, nor will it use the 204 DT_SONAME specified in the library. If specified multiple times 205 `DT_AUDIT' will contain a colon separated list of audit interfaces 206 to use. If the linker finds an object with an audit entry while 207 searching for shared libraries, it will add a corresponding 208 `DT_DEPAUDIT' entry in the output file. This option is only 209 meaningful on ELF platforms supporting the rtld-audit interface. 210 211`-A ARCHITECTURE' 212`--architecture=ARCHITECTURE' 213 In the current release of `ld', this option is useful only for the 214 Intel 960 family of architectures. In that `ld' configuration, the 215 ARCHITECTURE argument identifies the particular architecture in 216 the 960 family, enabling some safeguards and modifying the 217 archive-library search path. *Note `ld' and the Intel 960 family: 218 i960, for details. 219 220 Future releases of `ld' may support similar functionality for 221 other architecture families. 222 223`-b INPUT-FORMAT' 224`--format=INPUT-FORMAT' 225 `ld' may be configured to support more than one kind of object 226 file. If your `ld' is configured this way, you can use the `-b' 227 option to specify the binary format for input object files that 228 follow this option on the command line. Even when `ld' is 229 configured to support alternative object formats, you don't 230 usually need to specify this, as `ld' should be configured to 231 expect as a default input format the most usual format on each 232 machine. INPUT-FORMAT is a text string, the name of a particular 233 format supported by the BFD libraries. (You can list the 234 available binary formats with `objdump -i'.) *Note BFD::. 235 236 You may want to use this option if you are linking files with an 237 unusual binary format. You can also use `-b' to switch formats 238 explicitly (when linking object files of different formats), by 239 including `-b INPUT-FORMAT' before each group of object files in a 240 particular format. 241 242 The default format is taken from the environment variable 243 `GNUTARGET'. *Note Environment::. You can also define the input 244 format from a script, using the command `TARGET'; see *Note Format 245 Commands::. 246 247`-c MRI-COMMANDFILE' 248`--mri-script=MRI-COMMANDFILE' 249 For compatibility with linkers produced by MRI, `ld' accepts script 250 files written in an alternate, restricted command language, 251 described in *Note MRI Compatible Script Files: MRI. Introduce 252 MRI script files with the option `-c'; use the `-T' option to run 253 linker scripts written in the general-purpose `ld' scripting 254 language. If MRI-CMDFILE does not exist, `ld' looks for it in the 255 directories specified by any `-L' options. 256 257`-d' 258`-dc' 259`-dp' 260 These three options are equivalent; multiple forms are supported 261 for compatibility with other linkers. They assign space to common 262 symbols even if a relocatable output file is specified (with 263 `-r'). The script command `FORCE_COMMON_ALLOCATION' has the same 264 effect. *Note Miscellaneous Commands::. 265 266`--depaudit AUDITLIB' 267`-P AUDITLIB' 268 Adds AUDITLIB to the `DT_DEPAUDIT' entry of the dynamic section. 269 AUDITLIB is not checked for existence, nor will it use the 270 DT_SONAME specified in the library. If specified multiple times 271 `DT_DEPAUDIT' will contain a colon separated list of audit 272 interfaces to use. This option is only meaningful on ELF 273 platforms supporting the rtld-audit interface. The -P option is 274 provided for Solaris compatibility. 275 276`-e ENTRY' 277`--entry=ENTRY' 278 Use ENTRY as the explicit symbol for beginning execution of your 279 program, rather than the default entry point. If there is no 280 symbol named ENTRY, the linker will try to parse ENTRY as a number, 281 and use that as the entry address (the number will be interpreted 282 in base 10; you may use a leading `0x' for base 16, or a leading 283 `0' for base 8). *Note Entry Point::, for a discussion of defaults 284 and other ways of specifying the entry point. 285 286`--exclude-libs LIB,LIB,...' 287 Specifies a list of archive libraries from which symbols should 288 not be automatically exported. The library names may be delimited 289 by commas or colons. Specifying `--exclude-libs ALL' excludes 290 symbols in all archive libraries from automatic export. This 291 option is available only for the i386 PE targeted port of the 292 linker and for ELF targeted ports. For i386 PE, symbols 293 explicitly listed in a .def file are still exported, regardless of 294 this option. For ELF targeted ports, symbols affected by this 295 option will be treated as hidden. 296 297`--exclude-modules-for-implib MODULE,MODULE,...' 298 Specifies a list of object files or archive members, from which 299 symbols should not be automatically exported, but which should be 300 copied wholesale into the import library being generated during 301 the link. The module names may be delimited by commas or colons, 302 and must match exactly the filenames used by `ld' to open the 303 files; for archive members, this is simply the member name, but 304 for object files the name listed must include and match precisely 305 any path used to specify the input file on the linker's 306 command-line. This option is available only for the i386 PE 307 targeted port of the linker. Symbols explicitly listed in a .def 308 file are still exported, regardless of this option. 309 310`-E' 311`--export-dynamic' 312`--no-export-dynamic' 313 When creating a dynamically linked executable, using the `-E' 314 option or the `--export-dynamic' option causes the linker to add 315 all symbols to the dynamic symbol table. The dynamic symbol table 316 is the set of symbols which are visible from dynamic objects at 317 run time. 318 319 If you do not use either of these options (or use the 320 `--no-export-dynamic' option to restore the default behavior), the 321 dynamic symbol table will normally contain only those symbols 322 which are referenced by some dynamic object mentioned in the link. 323 324 If you use `dlopen' to load a dynamic object which needs to refer 325 back to the symbols defined by the program, rather than some other 326 dynamic object, then you will probably need to use this option when 327 linking the program itself. 328 329 You can also use the dynamic list to control what symbols should 330 be added to the dynamic symbol table if the output format supports 331 it. See the description of `--dynamic-list'. 332 333 Note that this option is specific to ELF targeted ports. PE 334 targets support a similar function to export all symbols from a 335 DLL or EXE; see the description of `--export-all-symbols' below. 336 337`-EB' 338 Link big-endian objects. This affects the default output format. 339 340`-EL' 341 Link little-endian objects. This affects the default output 342 format. 343 344`-f NAME' 345`--auxiliary=NAME' 346 When creating an ELF shared object, set the internal DT_AUXILIARY 347 field to the specified name. This tells the dynamic linker that 348 the symbol table of the shared object should be used as an 349 auxiliary filter on the symbol table of the shared object NAME. 350 351 If you later link a program against this filter object, then, when 352 you run the program, the dynamic linker will see the DT_AUXILIARY 353 field. If the dynamic linker resolves any symbols from the filter 354 object, it will first check whether there is a definition in the 355 shared object NAME. If there is one, it will be used instead of 356 the definition in the filter object. The shared object NAME need 357 not exist. Thus the shared object NAME may be used to provide an 358 alternative implementation of certain functions, perhaps for 359 debugging or for machine specific performance. 360 361 This option may be specified more than once. The DT_AUXILIARY 362 entries will be created in the order in which they appear on the 363 command line. 364 365`-F NAME' 366`--filter=NAME' 367 When creating an ELF shared object, set the internal DT_FILTER 368 field to the specified name. This tells the dynamic linker that 369 the symbol table of the shared object which is being created 370 should be used as a filter on the symbol table of the shared 371 object NAME. 372 373 If you later link a program against this filter object, then, when 374 you run the program, the dynamic linker will see the DT_FILTER 375 field. The dynamic linker will resolve symbols according to the 376 symbol table of the filter object as usual, but it will actually 377 link to the definitions found in the shared object NAME. Thus the 378 filter object can be used to select a subset of the symbols 379 provided by the object NAME. 380 381 Some older linkers used the `-F' option throughout a compilation 382 toolchain for specifying object-file format for both input and 383 output object files. The GNU linker uses other mechanisms for 384 this purpose: the `-b', `--format', `--oformat' options, the 385 `TARGET' command in linker scripts, and the `GNUTARGET' 386 environment variable. The GNU linker will ignore the `-F' option 387 when not creating an ELF shared object. 388 389`-fini=NAME' 390 When creating an ELF executable or shared object, call NAME when 391 the executable or shared object is unloaded, by setting DT_FINI to 392 the address of the function. By default, the linker uses `_fini' 393 as the function to call. 394 395`-g' 396 Ignored. Provided for compatibility with other tools. 397 398`-G VALUE' 399`--gpsize=VALUE' 400 Set the maximum size of objects to be optimized using the GP 401 register to SIZE. This is only meaningful for object file formats 402 such as MIPS ECOFF which supports putting large and small objects 403 into different sections. This is ignored for other object file 404 formats. 405 406`-h NAME' 407`-soname=NAME' 408 When creating an ELF shared object, set the internal DT_SONAME 409 field to the specified name. When an executable is linked with a 410 shared object which has a DT_SONAME field, then when the 411 executable is run the dynamic linker will attempt to load the 412 shared object specified by the DT_SONAME field rather than the 413 using the file name given to the linker. 414 415`-i' 416 Perform an incremental link (same as option `-r'). 417 418`-init=NAME' 419 When creating an ELF executable or shared object, call NAME when 420 the executable or shared object is loaded, by setting DT_INIT to 421 the address of the function. By default, the linker uses `_init' 422 as the function to call. 423 424`-l NAMESPEC' 425`--library=NAMESPEC' 426 Add the archive or object file specified by NAMESPEC to the list 427 of files to link. This option may be used any number of times. 428 If NAMESPEC is of the form `:FILENAME', `ld' will search the 429 library path for a file called FILENAME, otherwise it will search 430 the library path for a file called `libNAMESPEC.a'. 431 432 On systems which support shared libraries, `ld' may also search for 433 files other than `libNAMESPEC.a'. Specifically, on ELF and SunOS 434 systems, `ld' will search a directory for a library called 435 `libNAMESPEC.so' before searching for one called `libNAMESPEC.a'. 436 (By convention, a `.so' extension indicates a shared library.) 437 Note that this behavior does not apply to `:FILENAME', which 438 always specifies a file called FILENAME. 439 440 The linker will search an archive only once, at the location where 441 it is specified on the command line. If the archive defines a 442 symbol which was undefined in some object which appeared before 443 the archive on the command line, the linker will include the 444 appropriate file(s) from the archive. However, an undefined 445 symbol in an object appearing later on the command line will not 446 cause the linker to search the archive again. 447 448 See the `-(' option for a way to force the linker to search 449 archives multiple times. 450 451 You may list the same archive multiple times on the command line. 452 453 This type of archive searching is standard for Unix linkers. 454 However, if you are using `ld' on AIX, note that it is different 455 from the behaviour of the AIX linker. 456 457`-L SEARCHDIR' 458`--library-path=SEARCHDIR' 459 Add path SEARCHDIR to the list of paths that `ld' will search for 460 archive libraries and `ld' control scripts. You may use this 461 option any number of times. The directories are searched in the 462 order in which they are specified on the command line. 463 Directories specified on the command line are searched before the 464 default directories. All `-L' options apply to all `-l' options, 465 regardless of the order in which the options appear. `-L' options 466 do not affect how `ld' searches for a linker script unless `-T' 467 option is specified. 468 469 If SEARCHDIR begins with `=', then the `=' will be replaced by the 470 "sysroot prefix", a path specified when the linker is configured. 471 472 The default set of paths searched (without being specified with 473 `-L') depends on which emulation mode `ld' is using, and in some 474 cases also on how it was configured. *Note Environment::. 475 476 The paths can also be specified in a link script with the 477 `SEARCH_DIR' command. Directories specified this way are searched 478 at the point in which the linker script appears in the command 479 line. 480 481`-m EMULATION' 482 Emulate the EMULATION linker. You can list the available 483 emulations with the `--verbose' or `-V' options. 484 485 If the `-m' option is not used, the emulation is taken from the 486 `LDEMULATION' environment variable, if that is defined. 487 488 Otherwise, the default emulation depends upon how the linker was 489 configured. 490 491`-M' 492`--print-map' 493 Print a link map to the standard output. A link map provides 494 information about the link, including the following: 495 496 * Where object files are mapped into memory. 497 498 * How common symbols are allocated. 499 500 * All archive members included in the link, with a mention of 501 the symbol which caused the archive member to be brought in. 502 503 * The values assigned to symbols. 504 505 Note - symbols whose values are computed by an expression 506 which involves a reference to a previous value of the same 507 symbol may not have correct result displayed in the link map. 508 This is because the linker discards intermediate results and 509 only retains the final value of an expression. Under such 510 circumstances the linker will display the final value 511 enclosed by square brackets. Thus for example a linker 512 script containing: 513 514 foo = 1 515 foo = foo * 4 516 foo = foo + 8 517 518 will produce the following output in the link map if the `-M' 519 option is used: 520 521 0x00000001 foo = 0x1 522 [0x0000000c] foo = (foo * 0x4) 523 [0x0000000c] foo = (foo + 0x8) 524 525 See *Note Expressions:: for more information about 526 expressions in linker scripts. 527 528`-n' 529`--nmagic' 530 Turn off page alignment of sections, and disable linking against 531 shared libraries. If the output format supports Unix style magic 532 numbers, mark the output as `NMAGIC'. 533 534`-N' 535`--omagic' 536 Set the text and data sections to be readable and writable. Also, 537 do not page-align the data segment, and disable linking against 538 shared libraries. If the output format supports Unix style magic 539 numbers, mark the output as `OMAGIC'. Note: Although a writable 540 text section is allowed for PE-COFF targets, it does not conform 541 to the format specification published by Microsoft. 542 543`--no-omagic' 544 This option negates most of the effects of the `-N' option. It 545 sets the text section to be read-only, and forces the data segment 546 to be page-aligned. Note - this option does not enable linking 547 against shared libraries. Use `-Bdynamic' for this. 548 549`-o OUTPUT' 550`--output=OUTPUT' 551 Use OUTPUT as the name for the program produced by `ld'; if this 552 option is not specified, the name `a.out' is used by default. The 553 script command `OUTPUT' can also specify the output file name. 554 555`-O LEVEL' 556 If LEVEL is a numeric values greater than zero `ld' optimizes the 557 output. This might take significantly longer and therefore 558 probably should only be enabled for the final binary. At the 559 moment this option only affects ELF shared library generation. 560 Future releases of the linker may make more use of this option. 561 Also currently there is no difference in the linker's behaviour 562 for different non-zero values of this option. Again this may 563 change with future releases. 564 565`-q' 566`--emit-relocs' 567 Leave relocation sections and contents in fully linked executables. 568 Post link analysis and optimization tools may need this 569 information in order to perform correct modifications of 570 executables. This results in larger executables. 571 572 This option is currently only supported on ELF platforms. 573 574`--force-dynamic' 575 Force the output file to have dynamic sections. This option is 576 specific to VxWorks targets. 577 578`-r' 579`--relocatable' 580 Generate relocatable output--i.e., generate an output file that 581 can in turn serve as input to `ld'. This is often called "partial 582 linking". As a side effect, in environments that support standard 583 Unix magic numbers, this option also sets the output file's magic 584 number to `OMAGIC'. If this option is not specified, an absolute 585 file is produced. When linking C++ programs, this option _will 586 not_ resolve references to constructors; to do that, use `-Ur'. 587 588 When an input file does not have the same format as the output 589 file, partial linking is only supported if that input file does 590 not contain any relocations. Different output formats can have 591 further restrictions; for example some `a.out'-based formats do 592 not support partial linking with input files in other formats at 593 all. 594 595 This option does the same thing as `-i'. 596 597`-R FILENAME' 598`--just-symbols=FILENAME' 599 Read symbol names and their addresses from FILENAME, but do not 600 relocate it or include it in the output. This allows your output 601 file to refer symbolically to absolute locations of memory defined 602 in other programs. You may use this option more than once. 603 604 For compatibility with other ELF linkers, if the `-R' option is 605 followed by a directory name, rather than a file name, it is 606 treated as the `-rpath' option. 607 608`-s' 609`--strip-all' 610 Omit all symbol information from the output file. 611 612`-S' 613`--strip-debug' 614 Omit debugger symbol information (but not all symbols) from the 615 output file. 616 617`-t' 618`--trace' 619 Print the names of the input files as `ld' processes them. 620 621`-T SCRIPTFILE' 622`--script=SCRIPTFILE' 623 Use SCRIPTFILE as the linker script. This script replaces `ld''s 624 default linker script (rather than adding to it), so COMMANDFILE 625 must specify everything necessary to describe the output file. 626 *Note Scripts::. If SCRIPTFILE does not exist in the current 627 directory, `ld' looks for it in the directories specified by any 628 preceding `-L' options. Multiple `-T' options accumulate. 629 630`-dT SCRIPTFILE' 631`--default-script=SCRIPTFILE' 632 Use SCRIPTFILE as the default linker script. *Note Scripts::. 633 634 This option is similar to the `--script' option except that 635 processing of the script is delayed until after the rest of the 636 command line has been processed. This allows options placed after 637 the `--default-script' option on the command line to affect the 638 behaviour of the linker script, which can be important when the 639 linker command line cannot be directly controlled by the user. 640 (eg because the command line is being constructed by another tool, 641 such as `gcc'). 642 643`-u SYMBOL' 644`--undefined=SYMBOL' 645 Force SYMBOL to be entered in the output file as an undefined 646 symbol. Doing this may, for example, trigger linking of additional 647 modules from standard libraries. `-u' may be repeated with 648 different option arguments to enter additional undefined symbols. 649 This option is equivalent to the `EXTERN' linker script command. 650 651`-Ur' 652 For anything other than C++ programs, this option is equivalent to 653 `-r': it generates relocatable output--i.e., an output file that 654 can in turn serve as input to `ld'. When linking C++ programs, 655 `-Ur' _does_ resolve references to constructors, unlike `-r'. It 656 does not work to use `-Ur' on files that were themselves linked 657 with `-Ur'; once the constructor table has been built, it cannot 658 be added to. Use `-Ur' only for the last partial link, and `-r' 659 for the others. 660 661`--unique[=SECTION]' 662 Creates a separate output section for every input section matching 663 SECTION, or if the optional wildcard SECTION argument is missing, 664 for every orphan input section. An orphan section is one not 665 specifically mentioned in a linker script. You may use this option 666 multiple times on the command line; It prevents the normal 667 merging of input sections with the same name, overriding output 668 section assignments in a linker script. 669 670`-v' 671`--version' 672`-V' 673 Display the version number for `ld'. The `-V' option also lists 674 the supported emulations. 675 676`-x' 677`--discard-all' 678 Delete all local symbols. 679 680`-X' 681`--discard-locals' 682 Delete all temporary local symbols. (These symbols start with 683 system-specific local label prefixes, typically `.L' for ELF 684 systems or `L' for traditional a.out systems.) 685 686`-y SYMBOL' 687`--trace-symbol=SYMBOL' 688 Print the name of each linked file in which SYMBOL appears. This 689 option may be given any number of times. On many systems it is 690 necessary to prepend an underscore. 691 692 This option is useful when you have an undefined symbol in your 693 link but don't know where the reference is coming from. 694 695`-Y PATH' 696 Add PATH to the default library search path. This option exists 697 for Solaris compatibility. 698 699`-z KEYWORD' 700 The recognized keywords are: 701 `combreloc' 702 Combines multiple reloc sections and sorts them to make 703 dynamic symbol lookup caching possible. 704 705 `defs' 706 Disallows undefined symbols in object files. Undefined 707 symbols in shared libraries are still allowed. 708 709 `execstack' 710 Marks the object as requiring executable stack. 711 712 `initfirst' 713 This option is only meaningful when building a shared object. 714 It marks the object so that its runtime initialization will 715 occur before the runtime initialization of any other objects 716 brought into the process at the same time. Similarly the 717 runtime finalization of the object will occur after the 718 runtime finalization of any other objects. 719 720 `interpose' 721 Marks the object that its symbol table interposes before all 722 symbols but the primary executable. 723 724 `lazy' 725 When generating an executable or shared library, mark it to 726 tell the dynamic linker to defer function call resolution to 727 the point when the function is called (lazy binding), rather 728 than at load time. Lazy binding is the default. 729 730 `loadfltr' 731 Marks the object that its filters be processed immediately at 732 runtime. 733 734 `muldefs' 735 Allows multiple definitions. 736 737 `nocombreloc' 738 Disables multiple reloc sections combining. 739 740 `nocopyreloc' 741 Disables production of copy relocs. 742 743 `nodefaultlib' 744 Marks the object that the search for dependencies of this 745 object will ignore any default library search paths. 746 747 `nodelete' 748 Marks the object shouldn't be unloaded at runtime. 749 750 `nodlopen' 751 Marks the object not available to `dlopen'. 752 753 `nodump' 754 Marks the object can not be dumped by `dldump'. 755 756 `noexecstack' 757 Marks the object as not requiring executable stack. 758 759 `norelro' 760 Don't create an ELF `PT_GNU_RELRO' segment header in the 761 object. 762 763 `now' 764 When generating an executable or shared library, mark it to 765 tell the dynamic linker to resolve all symbols when the 766 program is started, or when the shared library is linked to 767 using dlopen, instead of deferring function call resolution 768 to the point when the function is first called. 769 770 `origin' 771 Marks the object may contain $ORIGIN. 772 773 `relro' 774 Create an ELF `PT_GNU_RELRO' segment header in the object. 775 776 `max-page-size=VALUE' 777 Set the emulation maximum page size to VALUE. 778 779 `common-page-size=VALUE' 780 Set the emulation common page size to VALUE. 781 782 783 Other keywords are ignored for Solaris compatibility. 784 785`-( ARCHIVES -)' 786`--start-group ARCHIVES --end-group' 787 The ARCHIVES should be a list of archive files. They may be 788 either explicit file names, or `-l' options. 789 790 The specified archives are searched repeatedly until no new 791 undefined references are created. Normally, an archive is 792 searched only once in the order that it is specified on the 793 command line. If a symbol in that archive is needed to resolve an 794 undefined symbol referred to by an object in an archive that 795 appears later on the command line, the linker would not be able to 796 resolve that reference. By grouping the archives, they all be 797 searched repeatedly until all possible references are resolved. 798 799 Using this option has a significant performance cost. It is best 800 to use it only when there are unavoidable circular references 801 between two or more archives. 802 803`--accept-unknown-input-arch' 804`--no-accept-unknown-input-arch' 805 Tells the linker to accept input files whose architecture cannot be 806 recognised. The assumption is that the user knows what they are 807 doing and deliberately wants to link in these unknown input files. 808 This was the default behaviour of the linker, before release 809 2.14. The default behaviour from release 2.14 onwards is to 810 reject such input files, and so the `--accept-unknown-input-arch' 811 option has been added to restore the old behaviour. 812 813`--as-needed' 814`--no-as-needed' 815 This option affects ELF DT_NEEDED tags for dynamic libraries 816 mentioned on the command line after the `--as-needed' option. 817 Normally the linker will add a DT_NEEDED tag for each dynamic 818 library mentioned on the command line, regardless of whether the 819 library is actually needed or not. `--as-needed' causes a 820 DT_NEEDED tag to only be emitted for a library that satisfies an 821 undefined symbol reference from a regular object file or, if the 822 library is not found in the DT_NEEDED lists of other libraries 823 linked up to that point, an undefined symbol reference from 824 another dynamic library. `--no-as-needed' restores the default 825 behaviour. 826 827`--add-needed' 828`--no-add-needed' 829 These two options have been deprecated because of the similarity of 830 their names to the `--as-needed' and `--no-as-needed' options. 831 They have been replaced by `--copy-dt-needed-entries' and 832 `--no-copy-dt-needed-entries'. 833 834`-assert KEYWORD' 835 This option is ignored for SunOS compatibility. 836 837`-Bdynamic' 838`-dy' 839`-call_shared' 840 Link against dynamic libraries. This is only meaningful on 841 platforms for which shared libraries are supported. This option 842 is normally the default on such platforms. The different variants 843 of this option are for compatibility with various systems. You 844 may use this option multiple times on the command line: it affects 845 library searching for `-l' options which follow it. 846 847`-Bgroup' 848 Set the `DF_1_GROUP' flag in the `DT_FLAGS_1' entry in the dynamic 849 section. This causes the runtime linker to handle lookups in this 850 object and its dependencies to be performed only inside the group. 851 `--unresolved-symbols=report-all' is implied. This option is only 852 meaningful on ELF platforms which support shared libraries. 853 854`-Bstatic' 855`-dn' 856`-non_shared' 857`-static' 858 Do not link against shared libraries. This is only meaningful on 859 platforms for which shared libraries are supported. The different 860 variants of this option are for compatibility with various 861 systems. You may use this option multiple times on the command 862 line: it affects library searching for `-l' options which follow 863 it. This option also implies `--unresolved-symbols=report-all'. 864 This option can be used with `-shared'. Doing so means that a 865 shared library is being created but that all of the library's 866 external references must be resolved by pulling in entries from 867 static libraries. 868 869`-Bsymbolic' 870 When creating a shared library, bind references to global symbols 871 to the definition within the shared library, if any. Normally, it 872 is possible for a program linked against a shared library to 873 override the definition within the shared library. This option is 874 only meaningful on ELF platforms which support shared libraries. 875 876`-Bsymbolic-functions' 877 When creating a shared library, bind references to global function 878 symbols to the definition within the shared library, if any. This 879 option is only meaningful on ELF platforms which support shared 880 libraries. 881 882`--dynamic-list=DYNAMIC-LIST-FILE' 883 Specify the name of a dynamic list file to the linker. This is 884 typically used when creating shared libraries to specify a list of 885 global symbols whose references shouldn't be bound to the 886 definition within the shared library, or creating dynamically 887 linked executables to specify a list of symbols which should be 888 added to the symbol table in the executable. This option is only 889 meaningful on ELF platforms which support shared libraries. 890 891 The format of the dynamic list is the same as the version node 892 without scope and node name. See *Note VERSION:: for more 893 information. 894 895`--dynamic-list-data' 896 Include all global data symbols to the dynamic list. 897 898`--dynamic-list-cpp-new' 899 Provide the builtin dynamic list for C++ operator new and delete. 900 It is mainly useful for building shared libstdc++. 901 902`--dynamic-list-cpp-typeinfo' 903 Provide the builtin dynamic list for C++ runtime type 904 identification. 905 906`--check-sections' 907`--no-check-sections' 908 Asks the linker _not_ to check section addresses after they have 909 been assigned to see if there are any overlaps. Normally the 910 linker will perform this check, and if it finds any overlaps it 911 will produce suitable error messages. The linker does know about, 912 and does make allowances for sections in overlays. The default 913 behaviour can be restored by using the command line switch 914 `--check-sections'. Section overlap is not usually checked for 915 relocatable links. You can force checking in that case by using 916 the `--check-sections' option. 917 918`--copy-dt-needed-entries' 919`--no-copy-dt-needed-entries' 920 This option affects the treatment of dynamic libraries referred to 921 by DT_NEEDED tags _inside_ ELF dynamic libraries mentioned on the 922 command line. Normally the linker will add a DT_NEEDED tag to the 923 output binary for each library mentioned in a DT_NEEDED tag in an 924 input dynamic library. With `--no-copy-dt-needed-entries' 925 specified on the command line however any dynamic libraries that 926 follow it will have their DT_NEEDED entries ignored. The default 927 behaviour can be restored with `--copy-dt-needed-entries'. 928 929 This option also has an effect on the resolution of symbols in 930 dynamic libraries. With the default setting dynamic libraries 931 mentioned on the command line will be recursively searched, 932 following their DT_NEEDED tags to other libraries, in order to 933 resolve symbols required by the output binary. With 934 `--no-copy-dt-needed-entries' specified however the searching of 935 dynamic libraries that follow it will stop with the dynamic 936 library itself. No DT_NEEDED links will be traversed to resolve 937 symbols. 938 939`--cref' 940 Output a cross reference table. If a linker map file is being 941 generated, the cross reference table is printed to the map file. 942 Otherwise, it is printed on the standard output. 943 944 The format of the table is intentionally simple, so that it may be 945 easily processed by a script if necessary. The symbols are 946 printed out, sorted by name. For each symbol, a list of file 947 names is given. If the symbol is defined, the first file listed 948 is the location of the definition. The remaining files contain 949 references to the symbol. 950 951`--no-define-common' 952 This option inhibits the assignment of addresses to common symbols. 953 The script command `INHIBIT_COMMON_ALLOCATION' has the same effect. 954 *Note Miscellaneous Commands::. 955 956 The `--no-define-common' option allows decoupling the decision to 957 assign addresses to Common symbols from the choice of the output 958 file type; otherwise a non-Relocatable output type forces 959 assigning addresses to Common symbols. Using `--no-define-common' 960 allows Common symbols that are referenced from a shared library to 961 be assigned addresses only in the main program. This eliminates 962 the unused duplicate space in the shared library, and also 963 prevents any possible confusion over resolving to the wrong 964 duplicate when there are many dynamic modules with specialized 965 search paths for runtime symbol resolution. 966 967`--defsym=SYMBOL=EXPRESSION' 968 Create a global symbol in the output file, containing the absolute 969 address given by EXPRESSION. You may use this option as many 970 times as necessary to define multiple symbols in the command line. 971 A limited form of arithmetic is supported for the EXPRESSION in 972 this context: you may give a hexadecimal constant or the name of 973 an existing symbol, or use `+' and `-' to add or subtract 974 hexadecimal constants or symbols. If you need more elaborate 975 expressions, consider using the linker command language from a 976 script (*note Assignment: Symbol Definitions: Assignments.). 977 _Note:_ there should be no white space between SYMBOL, the equals 978 sign ("<=>"), and EXPRESSION. 979 980`--demangle[=STYLE]' 981`--no-demangle' 982 These options control whether to demangle symbol names in error 983 messages and other output. When the linker is told to demangle, 984 it tries to present symbol names in a readable fashion: it strips 985 leading underscores if they are used by the object file format, 986 and converts C++ mangled symbol names into user readable names. 987 Different compilers have different mangling styles. The optional 988 demangling style argument can be used to choose an appropriate 989 demangling style for your compiler. The linker will demangle by 990 default unless the environment variable `COLLECT_NO_DEMANGLE' is 991 set. These options may be used to override the default. 992 993`-IFILE' 994`--dynamic-linker=FILE' 995 Set the name of the dynamic linker. This is only meaningful when 996 generating dynamically linked ELF executables. The default dynamic 997 linker is normally correct; don't use this unless you know what 998 you are doing. 999 1000`--fatal-warnings' 1001`--no-fatal-warnings' 1002 Treat all warnings as errors. The default behaviour can be 1003 restored with the option `--no-fatal-warnings'. 1004 1005`--force-exe-suffix' 1006 Make sure that an output file has a .exe suffix. 1007 1008 If a successfully built fully linked output file does not have a 1009 `.exe' or `.dll' suffix, this option forces the linker to copy the 1010 output file to one of the same name with a `.exe' suffix. This 1011 option is useful when using unmodified Unix makefiles on a 1012 Microsoft Windows host, since some versions of Windows won't run 1013 an image unless it ends in a `.exe' suffix. 1014 1015`--gc-sections' 1016`--no-gc-sections' 1017 Enable garbage collection of unused input sections. It is ignored 1018 on targets that do not support this option. The default behaviour 1019 (of not performing this garbage collection) can be restored by 1020 specifying `--no-gc-sections' on the command line. 1021 1022 `--gc-sections' decides which input sections are used by examining 1023 symbols and relocations. The section containing the entry symbol 1024 and all sections containing symbols undefined on the command-line 1025 will be kept, as will sections containing symbols referenced by 1026 dynamic objects. Note that when building shared libraries, the 1027 linker must assume that any visible symbol is referenced. Once 1028 this initial set of sections has been determined, the linker 1029 recursively marks as used any section referenced by their 1030 relocations. See `--entry' and `--undefined'. 1031 1032 This option can be set when doing a partial link (enabled with 1033 option `-r'). In this case the root of symbols kept must be 1034 explicitly specified either by an `--entry' or `--undefined' 1035 option or by a `ENTRY' command in the linker script. 1036 1037`--print-gc-sections' 1038`--no-print-gc-sections' 1039 List all sections removed by garbage collection. The listing is 1040 printed on stderr. This option is only effective if garbage 1041 collection has been enabled via the `--gc-sections') option. The 1042 default behaviour (of not listing the sections that are removed) 1043 can be restored by specifying `--no-print-gc-sections' on the 1044 command line. 1045 1046`--help' 1047 Print a summary of the command-line options on the standard output 1048 and exit. 1049 1050`--target-help' 1051 Print a summary of all target specific options on the standard 1052 output and exit. 1053 1054`-Map=MAPFILE' 1055 Print a link map to the file MAPFILE. See the description of the 1056 `-M' option, above. 1057 1058`--no-keep-memory' 1059 `ld' normally optimizes for speed over memory usage by caching the 1060 symbol tables of input files in memory. This option tells `ld' to 1061 instead optimize for memory usage, by rereading the symbol tables 1062 as necessary. This may be required if `ld' runs out of memory 1063 space while linking a large executable. 1064 1065`--no-undefined' 1066`-z defs' 1067 Report unresolved symbol references from regular object files. 1068 This is done even if the linker is creating a non-symbolic shared 1069 library. The switch `--[no-]allow-shlib-undefined' controls the 1070 behaviour for reporting unresolved references found in shared 1071 libraries being linked in. 1072 1073`--allow-multiple-definition' 1074`-z muldefs' 1075 Normally when a symbol is defined multiple times, the linker will 1076 report a fatal error. These options allow multiple definitions and 1077 the first definition will be used. 1078 1079`--allow-shlib-undefined' 1080`--no-allow-shlib-undefined' 1081 Allows or disallows undefined symbols in shared libraries. This 1082 switch is similar to `--no-undefined' except that it determines 1083 the behaviour when the undefined symbols are in a shared library 1084 rather than a regular object file. It does not affect how 1085 undefined symbols in regular object files are handled. 1086 1087 The default behaviour is to report errors for any undefined symbols 1088 referenced in shared libraries if the linker is being used to 1089 create an executable, but to allow them if the linker is being 1090 used to create a shared library. 1091 1092 The reasons for allowing undefined symbol references in shared 1093 libraries specified at link time are that: 1094 1095 * A shared library specified at link time may not be the same 1096 as the one that is available at load time, so the symbol 1097 might actually be resolvable at load time. 1098 1099 * There are some operating systems, eg BeOS and HPPA, where 1100 undefined symbols in shared libraries are normal. 1101 1102 The BeOS kernel for example patches shared libraries at load 1103 time to select whichever function is most appropriate for the 1104 current architecture. This is used, for example, to 1105 dynamically select an appropriate memset function. 1106 1107`--no-undefined-version' 1108 Normally when a symbol has an undefined version, the linker will 1109 ignore it. This option disallows symbols with undefined version 1110 and a fatal error will be issued instead. 1111 1112`--default-symver' 1113 Create and use a default symbol version (the soname) for 1114 unversioned exported symbols. 1115 1116`--default-imported-symver' 1117 Create and use a default symbol version (the soname) for 1118 unversioned imported symbols. 1119 1120`--no-warn-mismatch' 1121 Normally `ld' will give an error if you try to link together input 1122 files that are mismatched for some reason, perhaps because they 1123 have been compiled for different processors or for different 1124 endiannesses. This option tells `ld' that it should silently 1125 permit such possible errors. This option should only be used with 1126 care, in cases when you have taken some special action that 1127 ensures that the linker errors are inappropriate. 1128 1129`--no-warn-search-mismatch' 1130 Normally `ld' will give a warning if it finds an incompatible 1131 library during a library search. This option silences the warning. 1132 1133`--no-whole-archive' 1134 Turn off the effect of the `--whole-archive' option for subsequent 1135 archive files. 1136 1137`--noinhibit-exec' 1138 Retain the executable output file whenever it is still usable. 1139 Normally, the linker will not produce an output file if it 1140 encounters errors during the link process; it exits without 1141 writing an output file when it issues any error whatsoever. 1142 1143`-nostdlib' 1144 Only search library directories explicitly specified on the 1145 command line. Library directories specified in linker scripts 1146 (including linker scripts specified on the command line) are 1147 ignored. 1148 1149`--oformat=OUTPUT-FORMAT' 1150 `ld' may be configured to support more than one kind of object 1151 file. If your `ld' is configured this way, you can use the 1152 `--oformat' option to specify the binary format for the output 1153 object file. Even when `ld' is configured to support alternative 1154 object formats, you don't usually need to specify this, as `ld' 1155 should be configured to produce as a default output format the most 1156 usual format on each machine. OUTPUT-FORMAT is a text string, the 1157 name of a particular format supported by the BFD libraries. (You 1158 can list the available binary formats with `objdump -i'.) The 1159 script command `OUTPUT_FORMAT' can also specify the output format, 1160 but this option overrides it. *Note BFD::. 1161 1162`-pie' 1163`--pic-executable' 1164 Create a position independent executable. This is currently only 1165 supported on ELF platforms. Position independent executables are 1166 similar to shared libraries in that they are relocated by the 1167 dynamic linker to the virtual address the OS chooses for them 1168 (which can vary between invocations). Like normal dynamically 1169 linked executables they can be executed and symbols defined in the 1170 executable cannot be overridden by shared libraries. 1171 1172`-qmagic' 1173 This option is ignored for Linux compatibility. 1174 1175`-Qy' 1176 This option is ignored for SVR4 compatibility. 1177 1178`--relax' 1179`--no-relax' 1180 An option with machine dependent effects. This option is only 1181 supported on a few targets. *Note `ld' and the H8/300: H8/300. 1182 *Note `ld' and the Intel 960 family: i960. *Note `ld' and Xtensa 1183 Processors: Xtensa. *Note `ld' and the 68HC11 and 68HC12: 1184 M68HC11/68HC12. *Note `ld' and PowerPC 32-bit ELF Support: 1185 PowerPC ELF32. 1186 1187 On some platforms the `--relax' option performs target specific, 1188 global optimizations that become possible when the linker resolves 1189 addressing in the program, such as relaxing address modes, 1190 synthesizing new instructions, selecting shorter version of current 1191 instructions, and combinig constant values. 1192 1193 On some platforms these link time global optimizations may make 1194 symbolic debugging of the resulting executable impossible. This 1195 is known to be the case for the Matsushita MN10200 and MN10300 1196 family of processors. 1197 1198 On platforms where this is not supported, `--relax' is accepted, 1199 but ignored. 1200 1201 On platforms where `--relax' is accepted the option `--no-relax' 1202 can be used to disable the feature. 1203 1204`--retain-symbols-file=FILENAME' 1205 Retain _only_ the symbols listed in the file FILENAME, discarding 1206 all others. FILENAME is simply a flat file, with one symbol name 1207 per line. This option is especially useful in environments (such 1208 as VxWorks) where a large global symbol table is accumulated 1209 gradually, to conserve run-time memory. 1210 1211 `--retain-symbols-file' does _not_ discard undefined symbols, or 1212 symbols needed for relocations. 1213 1214 You may only specify `--retain-symbols-file' once in the command 1215 line. It overrides `-s' and `-S'. 1216 1217`-rpath=DIR' 1218 Add a directory to the runtime library search path. This is used 1219 when linking an ELF executable with shared objects. All `-rpath' 1220 arguments are concatenated and passed to the runtime linker, which 1221 uses them to locate shared objects at runtime. The `-rpath' 1222 option is also used when locating shared objects which are needed 1223 by shared objects explicitly included in the link; see the 1224 description of the `-rpath-link' option. If `-rpath' is not used 1225 when linking an ELF executable, the contents of the environment 1226 variable `LD_RUN_PATH' will be used if it is defined. 1227 1228 The `-rpath' option may also be used on SunOS. By default, on 1229 SunOS, the linker will form a runtime search patch out of all the 1230 `-L' options it is given. If a `-rpath' option is used, the 1231 runtime search path will be formed exclusively using the `-rpath' 1232 options, ignoring the `-L' options. This can be useful when using 1233 gcc, which adds many `-L' options which may be on NFS mounted file 1234 systems. 1235 1236 For compatibility with other ELF linkers, if the `-R' option is 1237 followed by a directory name, rather than a file name, it is 1238 treated as the `-rpath' option. 1239 1240`-rpath-link=DIR' 1241 When using ELF or SunOS, one shared library may require another. 1242 This happens when an `ld -shared' link includes a shared library 1243 as one of the input files. 1244 1245 When the linker encounters such a dependency when doing a 1246 non-shared, non-relocatable link, it will automatically try to 1247 locate the required shared library and include it in the link, if 1248 it is not included explicitly. In such a case, the `-rpath-link' 1249 option specifies the first set of directories to search. The 1250 `-rpath-link' option may specify a sequence of directory names 1251 either by specifying a list of names separated by colons, or by 1252 appearing multiple times. 1253 1254 This option should be used with caution as it overrides the search 1255 path that may have been hard compiled into a shared library. In 1256 such a case it is possible to use unintentionally a different 1257 search path than the runtime linker would do. 1258 1259 The linker uses the following search paths to locate required 1260 shared libraries: 1261 1. Any directories specified by `-rpath-link' options. 1262 1263 2. Any directories specified by `-rpath' options. The difference 1264 between `-rpath' and `-rpath-link' is that directories 1265 specified by `-rpath' options are included in the executable 1266 and used at runtime, whereas the `-rpath-link' option is only 1267 effective at link time. Searching `-rpath' in this way is 1268 only supported by native linkers and cross linkers which have 1269 been configured with the `--with-sysroot' option. 1270 1271 3. On an ELF system, for native linkers, if the `-rpath' and 1272 `-rpath-link' options were not used, search the contents of 1273 the environment variable `LD_RUN_PATH'. 1274 1275 4. On SunOS, if the `-rpath' option was not used, search any 1276 directories specified using `-L' options. 1277 1278 5. For a native linker, the search the contents of the 1279 environment variable `LD_LIBRARY_PATH'. 1280 1281 6. For a native ELF linker, the directories in `DT_RUNPATH' or 1282 `DT_RPATH' of a shared library are searched for shared 1283 libraries needed by it. The `DT_RPATH' entries are ignored if 1284 `DT_RUNPATH' entries exist. 1285 1286 7. The default directories, normally `/lib' and `/usr/lib'. 1287 1288 8. For a native linker on an ELF system, if the file 1289 `/etc/ld.so.conf' exists, the list of directories found in 1290 that file. 1291 1292 If the required shared library is not found, the linker will issue 1293 a warning and continue with the link. 1294 1295`-shared' 1296`-Bshareable' 1297 Create a shared library. This is currently only supported on ELF, 1298 XCOFF and SunOS platforms. On SunOS, the linker will 1299 automatically create a shared library if the `-e' option is not 1300 used and there are undefined symbols in the link. 1301 1302`--sort-common' 1303`--sort-common=ascending' 1304`--sort-common=descending' 1305 This option tells `ld' to sort the common symbols by alignment in 1306 ascending or descending order when it places them in the 1307 appropriate output sections. The symbol alignments considered are 1308 sixteen-byte or larger, eight-byte, four-byte, two-byte, and 1309 one-byte. This is to prevent gaps between symbols due to alignment 1310 constraints. If no sorting order is specified, then descending 1311 order is assumed. 1312 1313`--sort-section=name' 1314 This option will apply `SORT_BY_NAME' to all wildcard section 1315 patterns in the linker script. 1316 1317`--sort-section=alignment' 1318 This option will apply `SORT_BY_ALIGNMENT' to all wildcard section 1319 patterns in the linker script. 1320 1321`--split-by-file[=SIZE]' 1322 Similar to `--split-by-reloc' but creates a new output section for 1323 each input file when SIZE is reached. SIZE defaults to a size of 1324 1 if not given. 1325 1326`--split-by-reloc[=COUNT]' 1327 Tries to creates extra sections in the output file so that no 1328 single output section in the file contains more than COUNT 1329 relocations. This is useful when generating huge relocatable 1330 files for downloading into certain real time kernels with the COFF 1331 object file format; since COFF cannot represent more than 65535 1332 relocations in a single section. Note that this will fail to work 1333 with object file formats which do not support arbitrary sections. 1334 The linker will not split up individual input sections for 1335 redistribution, so if a single input section contains more than 1336 COUNT relocations one output section will contain that many 1337 relocations. COUNT defaults to a value of 32768. 1338 1339`--stats' 1340 Compute and display statistics about the operation of the linker, 1341 such as execution time and memory usage. 1342 1343`--sysroot=DIRECTORY' 1344 Use DIRECTORY as the location of the sysroot, overriding the 1345 configure-time default. This option is only supported by linkers 1346 that were configured using `--with-sysroot'. 1347 1348`--traditional-format' 1349 For some targets, the output of `ld' is different in some ways from 1350 the output of some existing linker. This switch requests `ld' to 1351 use the traditional format instead. 1352 1353 For example, on SunOS, `ld' combines duplicate entries in the 1354 symbol string table. This can reduce the size of an output file 1355 with full debugging information by over 30 percent. 1356 Unfortunately, the SunOS `dbx' program can not read the resulting 1357 program (`gdb' has no trouble). The `--traditional-format' switch 1358 tells `ld' to not combine duplicate entries. 1359 1360`--section-start=SECTIONNAME=ORG' 1361 Locate a section in the output file at the absolute address given 1362 by ORG. You may use this option as many times as necessary to 1363 locate multiple sections in the command line. ORG must be a 1364 single hexadecimal integer; for compatibility with other linkers, 1365 you may omit the leading `0x' usually associated with hexadecimal 1366 values. _Note:_ there should be no white space between 1367 SECTIONNAME, the equals sign ("<=>"), and ORG. 1368 1369`-Tbss=ORG' 1370`-Tdata=ORG' 1371`-Ttext=ORG' 1372 Same as `--section-start', with `.bss', `.data' or `.text' as the 1373 SECTIONNAME. 1374 1375`-Ttext-segment=ORG' 1376 When creating an ELF executable or shared object, it will set the 1377 address of the first byte of the text segment. 1378 1379`--unresolved-symbols=METHOD' 1380 Determine how to handle unresolved symbols. There are four 1381 possible values for `method': 1382 1383 `ignore-all' 1384 Do not report any unresolved symbols. 1385 1386 `report-all' 1387 Report all unresolved symbols. This is the default. 1388 1389 `ignore-in-object-files' 1390 Report unresolved symbols that are contained in shared 1391 libraries, but ignore them if they come from regular object 1392 files. 1393 1394 `ignore-in-shared-libs' 1395 Report unresolved symbols that come from regular object 1396 files, but ignore them if they come from shared libraries. 1397 This can be useful when creating a dynamic binary and it is 1398 known that all the shared libraries that it should be 1399 referencing are included on the linker's command line. 1400 1401 The behaviour for shared libraries on their own can also be 1402 controlled by the `--[no-]allow-shlib-undefined' option. 1403 1404 Normally the linker will generate an error message for each 1405 reported unresolved symbol but the option 1406 `--warn-unresolved-symbols' can change this to a warning. 1407 1408`--dll-verbose' 1409`--verbose[=NUMBER]' 1410 Display the version number for `ld' and list the linker emulations 1411 supported. Display which input files can and cannot be opened. 1412 Display the linker script being used by the linker. If the 1413 optional NUMBER argument > 1, plugin symbol status will also be 1414 displayed. 1415 1416`--version-script=VERSION-SCRIPTFILE' 1417 Specify the name of a version script to the linker. This is 1418 typically used when creating shared libraries to specify 1419 additional information about the version hierarchy for the library 1420 being created. This option is only fully supported on ELF 1421 platforms which support shared libraries; see *Note VERSION::. It 1422 is partially supported on PE platforms, which can use version 1423 scripts to filter symbol visibility in auto-export mode: any 1424 symbols marked `local' in the version script will not be exported. 1425 *Note WIN32::. 1426 1427`--warn-common' 1428 Warn when a common symbol is combined with another common symbol 1429 or with a symbol definition. Unix linkers allow this somewhat 1430 sloppy practise, but linkers on some other operating systems do 1431 not. This option allows you to find potential problems from 1432 combining global symbols. Unfortunately, some C libraries use 1433 this practise, so you may get some warnings about symbols in the 1434 libraries as well as in your programs. 1435 1436 There are three kinds of global symbols, illustrated here by C 1437 examples: 1438 1439 `int i = 1;' 1440 A definition, which goes in the initialized data section of 1441 the output file. 1442 1443 `extern int i;' 1444 An undefined reference, which does not allocate space. There 1445 must be either a definition or a common symbol for the 1446 variable somewhere. 1447 1448 `int i;' 1449 A common symbol. If there are only (one or more) common 1450 symbols for a variable, it goes in the uninitialized data 1451 area of the output file. The linker merges multiple common 1452 symbols for the same variable into a single symbol. If they 1453 are of different sizes, it picks the largest size. The 1454 linker turns a common symbol into a declaration, if there is 1455 a definition of the same variable. 1456 1457 The `--warn-common' option can produce five kinds of warnings. 1458 Each warning consists of a pair of lines: the first describes the 1459 symbol just encountered, and the second describes the previous 1460 symbol encountered with the same name. One or both of the two 1461 symbols will be a common symbol. 1462 1463 1. Turning a common symbol into a reference, because there is 1464 already a definition for the symbol. 1465 FILE(SECTION): warning: common of `SYMBOL' 1466 overridden by definition 1467 FILE(SECTION): warning: defined here 1468 1469 2. Turning a common symbol into a reference, because a later 1470 definition for the symbol is encountered. This is the same 1471 as the previous case, except that the symbols are encountered 1472 in a different order. 1473 FILE(SECTION): warning: definition of `SYMBOL' 1474 overriding common 1475 FILE(SECTION): warning: common is here 1476 1477 3. Merging a common symbol with a previous same-sized common 1478 symbol. 1479 FILE(SECTION): warning: multiple common 1480 of `SYMBOL' 1481 FILE(SECTION): warning: previous common is here 1482 1483 4. Merging a common symbol with a previous larger common symbol. 1484 FILE(SECTION): warning: common of `SYMBOL' 1485 overridden by larger common 1486 FILE(SECTION): warning: larger common is here 1487 1488 5. Merging a common symbol with a previous smaller common 1489 symbol. This is the same as the previous case, except that 1490 the symbols are encountered in a different order. 1491 FILE(SECTION): warning: common of `SYMBOL' 1492 overriding smaller common 1493 FILE(SECTION): warning: smaller common is here 1494 1495`--warn-constructors' 1496 Warn if any global constructors are used. This is only useful for 1497 a few object file formats. For formats like COFF or ELF, the 1498 linker can not detect the use of global constructors. 1499 1500`--warn-multiple-gp' 1501 Warn if multiple global pointer values are required in the output 1502 file. This is only meaningful for certain processors, such as the 1503 Alpha. Specifically, some processors put large-valued constants 1504 in a special section. A special register (the global pointer) 1505 points into the middle of this section, so that constants can be 1506 loaded efficiently via a base-register relative addressing mode. 1507 Since the offset in base-register relative mode is fixed and 1508 relatively small (e.g., 16 bits), this limits the maximum size of 1509 the constant pool. Thus, in large programs, it is often necessary 1510 to use multiple global pointer values in order to be able to 1511 address all possible constants. This option causes a warning to 1512 be issued whenever this case occurs. 1513 1514`--warn-once' 1515 Only warn once for each undefined symbol, rather than once per 1516 module which refers to it. 1517 1518`--warn-section-align' 1519 Warn if the address of an output section is changed because of 1520 alignment. Typically, the alignment will be set by an input 1521 section. The address will only be changed if it not explicitly 1522 specified; that is, if the `SECTIONS' command does not specify a 1523 start address for the section (*note SECTIONS::). 1524 1525`--warn-shared-textrel' 1526 Warn if the linker adds a DT_TEXTREL to a shared object. 1527 1528`--warn-alternate-em' 1529 Warn if an object has alternate ELF machine code. 1530 1531`--warn-unresolved-symbols' 1532 If the linker is going to report an unresolved symbol (see the 1533 option `--unresolved-symbols') it will normally generate an error. 1534 This option makes it generate a warning instead. 1535 1536`--error-unresolved-symbols' 1537 This restores the linker's default behaviour of generating errors 1538 when it is reporting unresolved symbols. 1539 1540`--whole-archive' 1541 For each archive mentioned on the command line after the 1542 `--whole-archive' option, include every object file in the archive 1543 in the link, rather than searching the archive for the required 1544 object files. This is normally used to turn an archive file into 1545 a shared library, forcing every object to be included in the 1546 resulting shared library. This option may be used more than once. 1547 1548 Two notes when using this option from gcc: First, gcc doesn't know 1549 about this option, so you have to use `-Wl,-whole-archive'. 1550 Second, don't forget to use `-Wl,-no-whole-archive' after your 1551 list of archives, because gcc will add its own list of archives to 1552 your link and you may not want this flag to affect those as well. 1553 1554`--wrap=SYMBOL' 1555 Use a wrapper function for SYMBOL. Any undefined reference to 1556 SYMBOL will be resolved to `__wrap_SYMBOL'. Any undefined 1557 reference to `__real_SYMBOL' will be resolved to SYMBOL. 1558 1559 This can be used to provide a wrapper for a system function. The 1560 wrapper function should be called `__wrap_SYMBOL'. If it wishes 1561 to call the system function, it should call `__real_SYMBOL'. 1562 1563 Here is a trivial example: 1564 1565 void * 1566 __wrap_malloc (size_t c) 1567 { 1568 printf ("malloc called with %zu\n", c); 1569 return __real_malloc (c); 1570 } 1571 1572 If you link other code with this file using `--wrap malloc', then 1573 all calls to `malloc' will call the function `__wrap_malloc' 1574 instead. The call to `__real_malloc' in `__wrap_malloc' will call 1575 the real `malloc' function. 1576 1577 You may wish to provide a `__real_malloc' function as well, so that 1578 links without the `--wrap' option will succeed. If you do this, 1579 you should not put the definition of `__real_malloc' in the same 1580 file as `__wrap_malloc'; if you do, the assembler may resolve the 1581 call before the linker has a chance to wrap it to `malloc'. 1582 1583`--eh-frame-hdr' 1584 Request creation of `.eh_frame_hdr' section and ELF 1585 `PT_GNU_EH_FRAME' segment header. 1586 1587`--enable-new-dtags' 1588`--disable-new-dtags' 1589 This linker can create the new dynamic tags in ELF. But the older 1590 ELF systems may not understand them. If you specify 1591 `--enable-new-dtags', the dynamic tags will be created as needed. 1592 If you specify `--disable-new-dtags', no new dynamic tags will be 1593 created. By default, the new dynamic tags are not created. Note 1594 that those options are only available for ELF systems. 1595 1596`--hash-size=NUMBER' 1597 Set the default size of the linker's hash tables to a prime number 1598 close to NUMBER. Increasing this value can reduce the length of 1599 time it takes the linker to perform its tasks, at the expense of 1600 increasing the linker's memory requirements. Similarly reducing 1601 this value can reduce the memory requirements at the expense of 1602 speed. 1603 1604`--hash-style=STYLE' 1605 Set the type of linker's hash table(s). STYLE can be either 1606 `sysv' for classic ELF `.hash' section, `gnu' for new style GNU 1607 `.gnu.hash' section or `both' for both the classic ELF `.hash' and 1608 new style GNU `.gnu.hash' hash tables. The default is `sysv'. 1609 1610`--reduce-memory-overheads' 1611 This option reduces memory requirements at ld runtime, at the 1612 expense of linking speed. This was introduced to select the old 1613 O(n^2) algorithm for link map file generation, rather than the new 1614 O(n) algorithm which uses about 40% more memory for symbol storage. 1615 1616 Another effect of the switch is to set the default hash table size 1617 to 1021, which again saves memory at the cost of lengthening the 1618 linker's run time. This is not done however if the `--hash-size' 1619 switch has been used. 1620 1621 The `--reduce-memory-overheads' switch may be also be used to 1622 enable other tradeoffs in future versions of the linker. 1623 1624`--build-id' 1625`--build-id=STYLE' 1626 Request creation of `.note.gnu.build-id' ELF note section. The 1627 contents of the note are unique bits identifying this linked file. 1628 STYLE can be `uuid' to use 128 random bits, `sha1' to use a 1629 160-bit SHA1 hash on the normative parts of the output contents, 1630 `md5' to use a 128-bit MD5 hash on the normative parts of the 1631 output contents, or `0xHEXSTRING' to use a chosen bit string 1632 specified as an even number of hexadecimal digits (`-' and `:' 1633 characters between digit pairs are ignored). If STYLE is omitted, 1634 `sha1' is used. 1635 1636 The `md5' and `sha1' styles produces an identifier that is always 1637 the same in an identical output file, but will be unique among all 1638 nonidentical output files. It is not intended to be compared as a 1639 checksum for the file's contents. A linked file may be changed 1640 later by other tools, but the build ID bit string identifying the 1641 original linked file does not change. 1642 1643 Passing `none' for STYLE disables the setting from any 1644 `--build-id' options earlier on the command line. 1645 16462.1.1 Options Specific to i386 PE Targets 1647----------------------------------------- 1648 1649The i386 PE linker supports the `-shared' option, which causes the 1650output to be a dynamically linked library (DLL) instead of a normal 1651executable. You should name the output `*.dll' when you use this 1652option. In addition, the linker fully supports the standard `*.def' 1653files, which may be specified on the linker command line like an object 1654file (in fact, it should precede archives it exports symbols from, to 1655ensure that they get linked in, just like a normal object file). 1656 1657 In addition to the options common to all targets, the i386 PE linker 1658support additional command line options that are specific to the i386 1659PE target. Options that take values may be separated from their values 1660by either a space or an equals sign. 1661 1662`--add-stdcall-alias' 1663 If given, symbols with a stdcall suffix (@NN) will be exported 1664 as-is and also with the suffix stripped. [This option is specific 1665 to the i386 PE targeted port of the linker] 1666 1667`--base-file FILE' 1668 Use FILE as the name of a file in which to save the base addresses 1669 of all the relocations needed for generating DLLs with `dlltool'. 1670 [This is an i386 PE specific option] 1671 1672`--dll' 1673 Create a DLL instead of a regular executable. You may also use 1674 `-shared' or specify a `LIBRARY' in a given `.def' file. [This 1675 option is specific to the i386 PE targeted port of the linker] 1676 1677`--enable-long-section-names' 1678`--disable-long-section-names' 1679 The PE variants of the Coff object format add an extension that 1680 permits the use of section names longer than eight characters, the 1681 normal limit for Coff. By default, these names are only allowed 1682 in object files, as fully-linked executable images do not carry 1683 the Coff string table required to support the longer names. As a 1684 GNU extension, it is possible to allow their use in executable 1685 images as well, or to (probably pointlessly!) disallow it in 1686 object files, by using these two options. Executable images 1687 generated with these long section names are slightly non-standard, 1688 carrying as they do a string table, and may generate confusing 1689 output when examined with non-GNU PE-aware tools, such as file 1690 viewers and dumpers. However, GDB relies on the use of PE long 1691 section names to find Dwarf-2 debug information sections in an 1692 executable image at runtime, and so if neither option is specified 1693 on the command-line, `ld' will enable long section names, 1694 overriding the default and technically correct behaviour, when it 1695 finds the presence of debug information while linking an executable 1696 image and not stripping symbols. [This option is valid for all PE 1697 targeted ports of the linker] 1698 1699`--enable-stdcall-fixup' 1700`--disable-stdcall-fixup' 1701 If the link finds a symbol that it cannot resolve, it will attempt 1702 to do "fuzzy linking" by looking for another defined symbol that 1703 differs only in the format of the symbol name (cdecl vs stdcall) 1704 and will resolve that symbol by linking to the match. For 1705 example, the undefined symbol `_foo' might be linked to the 1706 function `_foo@12', or the undefined symbol `_bar@16' might be 1707 linked to the function `_bar'. When the linker does this, it 1708 prints a warning, since it normally should have failed to link, 1709 but sometimes import libraries generated from third-party dlls may 1710 need this feature to be usable. If you specify 1711 `--enable-stdcall-fixup', this feature is fully enabled and 1712 warnings are not printed. If you specify 1713 `--disable-stdcall-fixup', this feature is disabled and such 1714 mismatches are considered to be errors. [This option is specific 1715 to the i386 PE targeted port of the linker] 1716 1717`--leading-underscore' 1718`--no-leading-underscore' 1719 For most targets default symbol-prefix is an underscore and is 1720 defined in target's description. By this option it is possible to 1721 disable/enable the default underscore symbol-prefix. 1722 1723`--export-all-symbols' 1724 If given, all global symbols in the objects used to build a DLL 1725 will be exported by the DLL. Note that this is the default if 1726 there otherwise wouldn't be any exported symbols. When symbols are 1727 explicitly exported via DEF files or implicitly exported via 1728 function attributes, the default is to not export anything else 1729 unless this option is given. Note that the symbols `DllMain@12', 1730 `DllEntryPoint@0', `DllMainCRTStartup@12', and `impure_ptr' will 1731 not be automatically exported. Also, symbols imported from other 1732 DLLs will not be re-exported, nor will symbols specifying the 1733 DLL's internal layout such as those beginning with `_head_' or 1734 ending with `_iname'. In addition, no symbols from `libgcc', 1735 `libstd++', `libmingw32', or `crtX.o' will be exported. Symbols 1736 whose names begin with `__rtti_' or `__builtin_' will not be 1737 exported, to help with C++ DLLs. Finally, there is an extensive 1738 list of cygwin-private symbols that are not exported (obviously, 1739 this applies on when building DLLs for cygwin targets). These 1740 cygwin-excludes are: `_cygwin_dll_entry@12', 1741 `_cygwin_crt0_common@8', `_cygwin_noncygwin_dll_entry@12', 1742 `_fmode', `_impure_ptr', `cygwin_attach_dll', `cygwin_premain0', 1743 `cygwin_premain1', `cygwin_premain2', `cygwin_premain3', and 1744 `environ'. [This option is specific to the i386 PE targeted port 1745 of the linker] 1746 1747`--exclude-symbols SYMBOL,SYMBOL,...' 1748 Specifies a list of symbols which should not be automatically 1749 exported. The symbol names may be delimited by commas or colons. 1750 [This option is specific to the i386 PE targeted port of the 1751 linker] 1752 1753`--exclude-all-symbols' 1754 Specifies no symbols should be automatically exported. [This 1755 option is specific to the i386 PE targeted port of the linker] 1756 1757`--file-alignment' 1758 Specify the file alignment. Sections in the file will always 1759 begin at file offsets which are multiples of this number. This 1760 defaults to 512. [This option is specific to the i386 PE targeted 1761 port of the linker] 1762 1763`--heap RESERVE' 1764`--heap RESERVE,COMMIT' 1765 Specify the number of bytes of memory to reserve (and optionally 1766 commit) to be used as heap for this program. The default is 1Mb 1767 reserved, 4K committed. [This option is specific to the i386 PE 1768 targeted port of the linker] 1769 1770`--image-base VALUE' 1771 Use VALUE as the base address of your program or dll. This is the 1772 lowest memory location that will be used when your program or dll 1773 is loaded. To reduce the need to relocate and improve performance 1774 of your dlls, each should have a unique base address and not 1775 overlap any other dlls. The default is 0x400000 for executables, 1776 and 0x10000000 for dlls. [This option is specific to the i386 PE 1777 targeted port of the linker] 1778 1779`--kill-at' 1780 If given, the stdcall suffixes (@NN) will be stripped from symbols 1781 before they are exported. [This option is specific to the i386 PE 1782 targeted port of the linker] 1783 1784`--large-address-aware' 1785 If given, the appropriate bit in the "Characteristics" field of 1786 the COFF header is set to indicate that this executable supports 1787 virtual addresses greater than 2 gigabytes. This should be used 1788 in conjunction with the /3GB or /USERVA=VALUE megabytes switch in 1789 the "[operating systems]" section of the BOOT.INI. Otherwise, 1790 this bit has no effect. [This option is specific to PE targeted 1791 ports of the linker] 1792 1793`--major-image-version VALUE' 1794 Sets the major number of the "image version". Defaults to 1. 1795 [This option is specific to the i386 PE targeted port of the 1796 linker] 1797 1798`--major-os-version VALUE' 1799 Sets the major number of the "os version". Defaults to 4. [This 1800 option is specific to the i386 PE targeted port of the linker] 1801 1802`--major-subsystem-version VALUE' 1803 Sets the major number of the "subsystem version". Defaults to 4. 1804 [This option is specific to the i386 PE targeted port of the 1805 linker] 1806 1807`--minor-image-version VALUE' 1808 Sets the minor number of the "image version". Defaults to 0. 1809 [This option is specific to the i386 PE targeted port of the 1810 linker] 1811 1812`--minor-os-version VALUE' 1813 Sets the minor number of the "os version". Defaults to 0. [This 1814 option is specific to the i386 PE targeted port of the linker] 1815 1816`--minor-subsystem-version VALUE' 1817 Sets the minor number of the "subsystem version". Defaults to 0. 1818 [This option is specific to the i386 PE targeted port of the 1819 linker] 1820 1821`--output-def FILE' 1822 The linker will create the file FILE which will contain a DEF file 1823 corresponding to the DLL the linker is generating. This DEF file 1824 (which should be called `*.def') may be used to create an import 1825 library with `dlltool' or may be used as a reference to 1826 automatically or implicitly exported symbols. [This option is 1827 specific to the i386 PE targeted port of the linker] 1828 1829`--out-implib FILE' 1830 The linker will create the file FILE which will contain an import 1831 lib corresponding to the DLL the linker is generating. This import 1832 lib (which should be called `*.dll.a' or `*.a' may be used to link 1833 clients against the generated DLL; this behaviour makes it 1834 possible to skip a separate `dlltool' import library creation step. 1835 [This option is specific to the i386 PE targeted port of the 1836 linker] 1837 1838`--enable-auto-image-base' 1839 Automatically choose the image base for DLLs, unless one is 1840 specified using the `--image-base' argument. By using a hash 1841 generated from the dllname to create unique image bases for each 1842 DLL, in-memory collisions and relocations which can delay program 1843 execution are avoided. [This option is specific to the i386 PE 1844 targeted port of the linker] 1845 1846`--disable-auto-image-base' 1847 Do not automatically generate a unique image base. If there is no 1848 user-specified image base (`--image-base') then use the platform 1849 default. [This option is specific to the i386 PE targeted port of 1850 the linker] 1851 1852`--dll-search-prefix STRING' 1853 When linking dynamically to a dll without an import library, 1854 search for `<string><basename>.dll' in preference to 1855 `lib<basename>.dll'. This behaviour allows easy distinction 1856 between DLLs built for the various "subplatforms": native, cygwin, 1857 uwin, pw, etc. For instance, cygwin DLLs typically use 1858 `--dll-search-prefix=cyg'. [This option is specific to the i386 1859 PE targeted port of the linker] 1860 1861`--enable-auto-import' 1862 Do sophisticated linking of `_symbol' to `__imp__symbol' for DATA 1863 imports from DLLs, and create the necessary thunking symbols when 1864 building the import libraries with those DATA exports. Note: Use 1865 of the 'auto-import' extension will cause the text section of the 1866 image file to be made writable. This does not conform to the 1867 PE-COFF format specification published by Microsoft. 1868 1869 Note - use of the 'auto-import' extension will also cause read only 1870 data which would normally be placed into the .rdata section to be 1871 placed into the .data section instead. This is in order to work 1872 around a problem with consts that is described here: 1873 http://www.cygwin.com/ml/cygwin/2004-09/msg01101.html 1874 1875 Using 'auto-import' generally will 'just work' - but sometimes you 1876 may see this message: 1877 1878 "variable '<var>' can't be auto-imported. Please read the 1879 documentation for ld's `--enable-auto-import' for details." 1880 1881 This message occurs when some (sub)expression accesses an address 1882 ultimately given by the sum of two constants (Win32 import tables 1883 only allow one). Instances where this may occur include accesses 1884 to member fields of struct variables imported from a DLL, as well 1885 as using a constant index into an array variable imported from a 1886 DLL. Any multiword variable (arrays, structs, long long, etc) may 1887 trigger this error condition. However, regardless of the exact 1888 data type of the offending exported variable, ld will always 1889 detect it, issue the warning, and exit. 1890 1891 There are several ways to address this difficulty, regardless of 1892 the data type of the exported variable: 1893 1894 One way is to use -enable-runtime-pseudo-reloc switch. This leaves 1895 the task of adjusting references in your client code for runtime 1896 environment, so this method works only when runtime environment 1897 supports this feature. 1898 1899 A second solution is to force one of the 'constants' to be a 1900 variable - that is, unknown and un-optimizable at compile time. 1901 For arrays, there are two possibilities: a) make the indexee (the 1902 array's address) a variable, or b) make the 'constant' index a 1903 variable. Thus: 1904 1905 extern type extern_array[]; 1906 extern_array[1] --> 1907 { volatile type *t=extern_array; t[1] } 1908 1909 or 1910 1911 extern type extern_array[]; 1912 extern_array[1] --> 1913 { volatile int t=1; extern_array[t] } 1914 1915 For structs (and most other multiword data types) the only option 1916 is to make the struct itself (or the long long, or the ...) 1917 variable: 1918 1919 extern struct s extern_struct; 1920 extern_struct.field --> 1921 { volatile struct s *t=&extern_struct; t->field } 1922 1923 or 1924 1925 extern long long extern_ll; 1926 extern_ll --> 1927 { volatile long long * local_ll=&extern_ll; *local_ll } 1928 1929 A third method of dealing with this difficulty is to abandon 1930 'auto-import' for the offending symbol and mark it with 1931 `__declspec(dllimport)'. However, in practise that requires using 1932 compile-time #defines to indicate whether you are building a DLL, 1933 building client code that will link to the DLL, or merely 1934 building/linking to a static library. In making the choice 1935 between the various methods of resolving the 'direct address with 1936 constant offset' problem, you should consider typical real-world 1937 usage: 1938 1939 Original: 1940 --foo.h 1941 extern int arr[]; 1942 --foo.c 1943 #include "foo.h" 1944 void main(int argc, char **argv){ 1945 printf("%d\n",arr[1]); 1946 } 1947 1948 Solution 1: 1949 --foo.h 1950 extern int arr[]; 1951 --foo.c 1952 #include "foo.h" 1953 void main(int argc, char **argv){ 1954 /* This workaround is for win32 and cygwin; do not "optimize" */ 1955 volatile int *parr = arr; 1956 printf("%d\n",parr[1]); 1957 } 1958 1959 Solution 2: 1960 --foo.h 1961 /* Note: auto-export is assumed (no __declspec(dllexport)) */ 1962 #if (defined(_WIN32) || defined(__CYGWIN__)) && \ 1963 !(defined(FOO_BUILD_DLL) || defined(FOO_STATIC)) 1964 #define FOO_IMPORT __declspec(dllimport) 1965 #else 1966 #define FOO_IMPORT 1967 #endif 1968 extern FOO_IMPORT int arr[]; 1969 --foo.c 1970 #include "foo.h" 1971 void main(int argc, char **argv){ 1972 printf("%d\n",arr[1]); 1973 } 1974 1975 A fourth way to avoid this problem is to re-code your library to 1976 use a functional interface rather than a data interface for the 1977 offending variables (e.g. set_foo() and get_foo() accessor 1978 functions). [This option is specific to the i386 PE targeted port 1979 of the linker] 1980 1981`--disable-auto-import' 1982 Do not attempt to do sophisticated linking of `_symbol' to 1983 `__imp__symbol' for DATA imports from DLLs. [This option is 1984 specific to the i386 PE targeted port of the linker] 1985 1986`--enable-runtime-pseudo-reloc' 1987 If your code contains expressions described in -enable-auto-import 1988 section, that is, DATA imports from DLL with non-zero offset, this 1989 switch will create a vector of 'runtime pseudo relocations' which 1990 can be used by runtime environment to adjust references to such 1991 data in your client code. [This option is specific to the i386 PE 1992 targeted port of the linker] 1993 1994`--disable-runtime-pseudo-reloc' 1995 Do not create pseudo relocations for non-zero offset DATA imports 1996 from DLLs. This is the default. [This option is specific to the 1997 i386 PE targeted port of the linker] 1998 1999`--enable-extra-pe-debug' 2000 Show additional debug info related to auto-import symbol thunking. 2001 [This option is specific to the i386 PE targeted port of the 2002 linker] 2003 2004`--section-alignment' 2005 Sets the section alignment. Sections in memory will always begin 2006 at addresses which are a multiple of this number. Defaults to 2007 0x1000. [This option is specific to the i386 PE targeted port of 2008 the linker] 2009 2010`--stack RESERVE' 2011`--stack RESERVE,COMMIT' 2012 Specify the number of bytes of memory to reserve (and optionally 2013 commit) to be used as stack for this program. The default is 2Mb 2014 reserved, 4K committed. [This option is specific to the i386 PE 2015 targeted port of the linker] 2016 2017`--subsystem WHICH' 2018`--subsystem WHICH:MAJOR' 2019`--subsystem WHICH:MAJOR.MINOR' 2020 Specifies the subsystem under which your program will execute. The 2021 legal values for WHICH are `native', `windows', `console', 2022 `posix', and `xbox'. You may optionally set the subsystem version 2023 also. Numeric values are also accepted for WHICH. [This option 2024 is specific to the i386 PE targeted port of the linker] 2025 2026 The following options set flags in the `DllCharacteristics' field 2027 of the PE file header: [These options are specific to PE targeted 2028 ports of the linker] 2029 2030`--dynamicbase' 2031 The image base address may be relocated using address space layout 2032 randomization (ASLR). This feature was introduced with MS Windows 2033 Vista for i386 PE targets. 2034 2035`--forceinteg' 2036 Code integrity checks are enforced. 2037 2038`--nxcompat' 2039 The image is compatible with the Data Execution Prevention. This 2040 feature was introduced with MS Windows XP SP2 for i386 PE targets. 2041 2042`--no-isolation' 2043 Although the image understands isolation, do not isolate the image. 2044 2045`--no-seh' 2046 The image does not use SEH. No SE handler may be called from this 2047 image. 2048 2049`--no-bind' 2050 Do not bind this image. 2051 2052`--wdmdriver' 2053 The driver uses the MS Windows Driver Model. 2054 2055`--tsaware' 2056 The image is Terminal Server aware. 2057 2058 20592.1.2 Options specific to Motorola 68HC11 and 68HC12 targets 2060------------------------------------------------------------ 2061 2062The 68HC11 and 68HC12 linkers support specific options to control the 2063memory bank switching mapping and trampoline code generation. 2064 2065`--no-trampoline' 2066 This option disables the generation of trampoline. By default a 2067 trampoline is generated for each far function which is called 2068 using a `jsr' instruction (this happens when a pointer to a far 2069 function is taken). 2070 2071`--bank-window NAME' 2072 This option indicates to the linker the name of the memory region 2073 in the `MEMORY' specification that describes the memory bank 2074 window. The definition of such region is then used by the linker 2075 to compute paging and addresses within the memory window. 2076 2077 20782.1.3 Options specific to Motorola 68K target 2079--------------------------------------------- 2080 2081The following options are supported to control handling of GOT 2082generation when linking for 68K targets. 2083 2084`--got=TYPE' 2085 This option tells the linker which GOT generation scheme to use. 2086 TYPE should be one of `single', `negative', `multigot' or 2087 `target'. For more information refer to the Info entry for `ld'. 2088 2089 2090 2091File: ld.info, Node: Environment, Prev: Options, Up: Invocation 2092 20932.2 Environment Variables 2094========================= 2095 2096You can change the behaviour of `ld' with the environment variables 2097`GNUTARGET', `LDEMULATION' and `COLLECT_NO_DEMANGLE'. 2098 2099 `GNUTARGET' determines the input-file object format if you don't use 2100`-b' (or its synonym `--format'). Its value should be one of the BFD 2101names for an input format (*note BFD::). If there is no `GNUTARGET' in 2102the environment, `ld' uses the natural format of the target. If 2103`GNUTARGET' is set to `default' then BFD attempts to discover the input 2104format by examining binary input files; this method often succeeds, but 2105there are potential ambiguities, since there is no method of ensuring 2106that the magic number used to specify object-file formats is unique. 2107However, the configuration procedure for BFD on each system places the 2108conventional format for that system first in the search-list, so 2109ambiguities are resolved in favor of convention. 2110 2111 `LDEMULATION' determines the default emulation if you don't use the 2112`-m' option. The emulation can affect various aspects of linker 2113behaviour, particularly the default linker script. You can list the 2114available emulations with the `--verbose' or `-V' options. If the `-m' 2115option is not used, and the `LDEMULATION' environment variable is not 2116defined, the default emulation depends upon how the linker was 2117configured. 2118 2119 Normally, the linker will default to demangling symbols. However, if 2120`COLLECT_NO_DEMANGLE' is set in the environment, then it will default 2121to not demangling symbols. This environment variable is used in a 2122similar fashion by the `gcc' linker wrapper program. The default may 2123be overridden by the `--demangle' and `--no-demangle' options. 2124 2125 2126File: ld.info, Node: Scripts, Next: Machine Dependent, Prev: Invocation, Up: Top 2127 21283 Linker Scripts 2129**************** 2130 2131Every link is controlled by a "linker script". This script is written 2132in the linker command language. 2133 2134 The main purpose of the linker script is to describe how the 2135sections in the input files should be mapped into the output file, and 2136to control the memory layout of the output file. Most linker scripts 2137do nothing more than this. However, when necessary, the linker script 2138can also direct the linker to perform many other operations, using the 2139commands described below. 2140 2141 The linker always uses a linker script. If you do not supply one 2142yourself, the linker will use a default script that is compiled into the 2143linker executable. You can use the `--verbose' command line option to 2144display the default linker script. Certain command line options, such 2145as `-r' or `-N', will affect the default linker script. 2146 2147 You may supply your own linker script by using the `-T' command line 2148option. When you do this, your linker script will replace the default 2149linker script. 2150 2151 You may also use linker scripts implicitly by naming them as input 2152files to the linker, as though they were files to be linked. *Note 2153Implicit Linker Scripts::. 2154 2155* Menu: 2156 2157* Basic Script Concepts:: Basic Linker Script Concepts 2158* Script Format:: Linker Script Format 2159* Simple Example:: Simple Linker Script Example 2160* Simple Commands:: Simple Linker Script Commands 2161* Assignments:: Assigning Values to Symbols 2162* SECTIONS:: SECTIONS Command 2163* MEMORY:: MEMORY Command 2164* PHDRS:: PHDRS Command 2165* VERSION:: VERSION Command 2166* Expressions:: Expressions in Linker Scripts 2167* Implicit Linker Scripts:: Implicit Linker Scripts 2168 2169 2170File: ld.info, Node: Basic Script Concepts, Next: Script Format, Up: Scripts 2171 21723.1 Basic Linker Script Concepts 2173================================ 2174 2175We need to define some basic concepts and vocabulary in order to 2176describe the linker script language. 2177 2178 The linker combines input files into a single output file. The 2179output file and each input file are in a special data format known as an 2180"object file format". Each file is called an "object file". The 2181output file is often called an "executable", but for our purposes we 2182will also call it an object file. Each object file has, among other 2183things, a list of "sections". We sometimes refer to a section in an 2184input file as an "input section"; similarly, a section in the output 2185file is an "output section". 2186 2187 Each section in an object file has a name and a size. Most sections 2188also have an associated block of data, known as the "section contents". 2189A section may be marked as "loadable", which mean that the contents 2190should be loaded into memory when the output file is run. A section 2191with no contents may be "allocatable", which means that an area in 2192memory should be set aside, but nothing in particular should be loaded 2193there (in some cases this memory must be zeroed out). A section which 2194is neither loadable nor allocatable typically contains some sort of 2195debugging information. 2196 2197 Every loadable or allocatable output section has two addresses. The 2198first is the "VMA", or virtual memory address. This is the address the 2199section will have when the output file is run. The second is the 2200"LMA", or load memory address. This is the address at which the 2201section will be loaded. In most cases the two addresses will be the 2202same. An example of when they might be different is when a data section 2203is loaded into ROM, and then copied into RAM when the program starts up 2204(this technique is often used to initialize global variables in a ROM 2205based system). In this case the ROM address would be the LMA, and the 2206RAM address would be the VMA. 2207 2208 You can see the sections in an object file by using the `objdump' 2209program with the `-h' option. 2210 2211 Every object file also has a list of "symbols", known as the "symbol 2212table". A symbol may be defined or undefined. Each symbol has a name, 2213and each defined symbol has an address, among other information. If 2214you compile a C or C++ program into an object file, you will get a 2215defined symbol for every defined function and global or static 2216variable. Every undefined function or global variable which is 2217referenced in the input file will become an undefined symbol. 2218 2219 You can see the symbols in an object file by using the `nm' program, 2220or by using the `objdump' program with the `-t' option. 2221 2222 2223File: ld.info, Node: Script Format, Next: Simple Example, Prev: Basic Script Concepts, Up: Scripts 2224 22253.2 Linker Script Format 2226======================== 2227 2228Linker scripts are text files. 2229 2230 You write a linker script as a series of commands. Each command is 2231either a keyword, possibly followed by arguments, or an assignment to a 2232symbol. You may separate commands using semicolons. Whitespace is 2233generally ignored. 2234 2235 Strings such as file or format names can normally be entered 2236directly. If the file name contains a character such as a comma which 2237would otherwise serve to separate file names, you may put the file name 2238in double quotes. There is no way to use a double quote character in a 2239file name. 2240 2241 You may include comments in linker scripts just as in C, delimited by 2242`/*' and `*/'. As in C, comments are syntactically equivalent to 2243whitespace. 2244 2245 2246File: ld.info, Node: Simple Example, Next: Simple Commands, Prev: Script Format, Up: Scripts 2247 22483.3 Simple Linker Script Example 2249================================ 2250 2251Many linker scripts are fairly simple. 2252 2253 The simplest possible linker script has just one command: 2254`SECTIONS'. You use the `SECTIONS' command to describe the memory 2255layout of the output file. 2256 2257 The `SECTIONS' command is a powerful command. Here we will describe 2258a simple use of it. Let's assume your program consists only of code, 2259initialized data, and uninitialized data. These will be in the 2260`.text', `.data', and `.bss' sections, respectively. Let's assume 2261further that these are the only sections which appear in your input 2262files. 2263 2264 For this example, let's say that the code should be loaded at address 22650x10000, and that the data should start at address 0x8000000. Here is a 2266linker script which will do that: 2267 SECTIONS 2268 { 2269 . = 0x10000; 2270 .text : { *(.text) } 2271 . = 0x8000000; 2272 .data : { *(.data) } 2273 .bss : { *(.bss) } 2274 } 2275 2276 You write the `SECTIONS' command as the keyword `SECTIONS', followed 2277by a series of symbol assignments and output section descriptions 2278enclosed in curly braces. 2279 2280 The first line inside the `SECTIONS' command of the above example 2281sets the value of the special symbol `.', which is the location 2282counter. If you do not specify the address of an output section in some 2283other way (other ways are described later), the address is set from the 2284current value of the location counter. The location counter is then 2285incremented by the size of the output section. At the start of the 2286`SECTIONS' command, the location counter has the value `0'. 2287 2288 The second line defines an output section, `.text'. The colon is 2289required syntax which may be ignored for now. Within the curly braces 2290after the output section name, you list the names of the input sections 2291which should be placed into this output section. The `*' is a wildcard 2292which matches any file name. The expression `*(.text)' means all 2293`.text' input sections in all input files. 2294 2295 Since the location counter is `0x10000' when the output section 2296`.text' is defined, the linker will set the address of the `.text' 2297section in the output file to be `0x10000'. 2298 2299 The remaining lines define the `.data' and `.bss' sections in the 2300output file. The linker will place the `.data' output section at 2301address `0x8000000'. After the linker places the `.data' output 2302section, the value of the location counter will be `0x8000000' plus the 2303size of the `.data' output section. The effect is that the linker will 2304place the `.bss' output section immediately after the `.data' output 2305section in memory. 2306 2307 The linker will ensure that each output section has the required 2308alignment, by increasing the location counter if necessary. In this 2309example, the specified addresses for the `.text' and `.data' sections 2310will probably satisfy any alignment constraints, but the linker may 2311have to create a small gap between the `.data' and `.bss' sections. 2312 2313 That's it! That's a simple and complete linker script. 2314 2315 2316File: ld.info, Node: Simple Commands, Next: Assignments, Prev: Simple Example, Up: Scripts 2317 23183.4 Simple Linker Script Commands 2319================================= 2320 2321In this section we describe the simple linker script commands. 2322 2323* Menu: 2324 2325* Entry Point:: Setting the entry point 2326* File Commands:: Commands dealing with files 2327 2328* Format Commands:: Commands dealing with object file formats 2329 2330* REGION_ALIAS:: Assign alias names to memory regions 2331* Miscellaneous Commands:: Other linker script commands 2332 2333 2334File: ld.info, Node: Entry Point, Next: File Commands, Up: Simple Commands 2335 23363.4.1 Setting the Entry Point 2337----------------------------- 2338 2339The first instruction to execute in a program is called the "entry 2340point". You can use the `ENTRY' linker script command to set the entry 2341point. The argument is a symbol name: 2342 ENTRY(SYMBOL) 2343 2344 There are several ways to set the entry point. The linker will set 2345the entry point by trying each of the following methods in order, and 2346stopping when one of them succeeds: 2347 * the `-e' ENTRY command-line option; 2348 2349 * the `ENTRY(SYMBOL)' command in a linker script; 2350 2351 * the value of a target specific symbol, if it is defined; For many 2352 targets this is `start', but PE and BeOS based systems for example 2353 check a list of possible entry symbols, matching the first one 2354 found. 2355 2356 * the address of the first byte of the `.text' section, if present; 2357 2358 * The address `0'. 2359 2360 2361File: ld.info, Node: File Commands, Next: Format Commands, Prev: Entry Point, Up: Simple Commands 2362 23633.4.2 Commands Dealing with Files 2364--------------------------------- 2365 2366Several linker script commands deal with files. 2367 2368`INCLUDE FILENAME' 2369 Include the linker script FILENAME at this point. The file will 2370 be searched for in the current directory, and in any directory 2371 specified with the `-L' option. You can nest calls to `INCLUDE' 2372 up to 10 levels deep. 2373 2374 You can place `INCLUDE' directives at the top level, in `MEMORY' or 2375 `SECTIONS' commands, or in output section descriptions. 2376 2377`INPUT(FILE, FILE, ...)' 2378`INPUT(FILE FILE ...)' 2379 The `INPUT' command directs the linker to include the named files 2380 in the link, as though they were named on the command line. 2381 2382 For example, if you always want to include `subr.o' any time you do 2383 a link, but you can't be bothered to put it on every link command 2384 line, then you can put `INPUT (subr.o)' in your linker script. 2385 2386 In fact, if you like, you can list all of your input files in the 2387 linker script, and then invoke the linker with nothing but a `-T' 2388 option. 2389 2390 In case a "sysroot prefix" is configured, and the filename starts 2391 with the `/' character, and the script being processed was located 2392 inside the "sysroot prefix", the filename will be looked for in 2393 the "sysroot prefix". Otherwise, the linker will try to open the 2394 file in the current directory. If it is not found, the linker 2395 will search through the archive library search path. See the 2396 description of `-L' in *Note Command Line Options: Options. 2397 2398 If you use `INPUT (-lFILE)', `ld' will transform the name to 2399 `libFILE.a', as with the command line argument `-l'. 2400 2401 When you use the `INPUT' command in an implicit linker script, the 2402 files will be included in the link at the point at which the linker 2403 script file is included. This can affect archive searching. 2404 2405`GROUP(FILE, FILE, ...)' 2406`GROUP(FILE FILE ...)' 2407 The `GROUP' command is like `INPUT', except that the named files 2408 should all be archives, and they are searched repeatedly until no 2409 new undefined references are created. See the description of `-(' 2410 in *Note Command Line Options: Options. 2411 2412`AS_NEEDED(FILE, FILE, ...)' 2413`AS_NEEDED(FILE FILE ...)' 2414 This construct can appear only inside of the `INPUT' or `GROUP' 2415 commands, among other filenames. The files listed will be handled 2416 as if they appear directly in the `INPUT' or `GROUP' commands, 2417 with the exception of ELF shared libraries, that will be added only 2418 when they are actually needed. This construct essentially enables 2419 `--as-needed' option for all the files listed inside of it and 2420 restores previous `--as-needed' resp. `--no-as-needed' setting 2421 afterwards. 2422 2423`OUTPUT(FILENAME)' 2424 The `OUTPUT' command names the output file. Using 2425 `OUTPUT(FILENAME)' in the linker script is exactly like using `-o 2426 FILENAME' on the command line (*note Command Line Options: 2427 Options.). If both are used, the command line option takes 2428 precedence. 2429 2430 You can use the `OUTPUT' command to define a default name for the 2431 output file other than the usual default of `a.out'. 2432 2433`SEARCH_DIR(PATH)' 2434 The `SEARCH_DIR' command adds PATH to the list of paths where `ld' 2435 looks for archive libraries. Using `SEARCH_DIR(PATH)' is exactly 2436 like using `-L PATH' on the command line (*note Command Line 2437 Options: Options.). If both are used, then the linker will search 2438 both paths. Paths specified using the command line option are 2439 searched first. 2440 2441`STARTUP(FILENAME)' 2442 The `STARTUP' command is just like the `INPUT' command, except 2443 that FILENAME will become the first input file to be linked, as 2444 though it were specified first on the command line. This may be 2445 useful when using a system in which the entry point is always the 2446 start of the first file. 2447 2448 2449File: ld.info, Node: Format Commands, Next: REGION_ALIAS, Prev: File Commands, Up: Simple Commands 2450 24513.4.3 Commands Dealing with Object File Formats 2452----------------------------------------------- 2453 2454A couple of linker script commands deal with object file formats. 2455 2456`OUTPUT_FORMAT(BFDNAME)' 2457`OUTPUT_FORMAT(DEFAULT, BIG, LITTLE)' 2458 The `OUTPUT_FORMAT' command names the BFD format to use for the 2459 output file (*note BFD::). Using `OUTPUT_FORMAT(BFDNAME)' is 2460 exactly like using `--oformat BFDNAME' on the command line (*note 2461 Command Line Options: Options.). If both are used, the command 2462 line option takes precedence. 2463 2464 You can use `OUTPUT_FORMAT' with three arguments to use different 2465 formats based on the `-EB' and `-EL' command line options. This 2466 permits the linker script to set the output format based on the 2467 desired endianness. 2468 2469 If neither `-EB' nor `-EL' are used, then the output format will 2470 be the first argument, DEFAULT. If `-EB' is used, the output 2471 format will be the second argument, BIG. If `-EL' is used, the 2472 output format will be the third argument, LITTLE. 2473 2474 For example, the default linker script for the MIPS ELF target 2475 uses this command: 2476 OUTPUT_FORMAT(elf32-bigmips, elf32-bigmips, elf32-littlemips) 2477 This says that the default format for the output file is 2478 `elf32-bigmips', but if the user uses the `-EL' command line 2479 option, the output file will be created in the `elf32-littlemips' 2480 format. 2481 2482`TARGET(BFDNAME)' 2483 The `TARGET' command names the BFD format to use when reading input 2484 files. It affects subsequent `INPUT' and `GROUP' commands. This 2485 command is like using `-b BFDNAME' on the command line (*note 2486 Command Line Options: Options.). If the `TARGET' command is used 2487 but `OUTPUT_FORMAT' is not, then the last `TARGET' command is also 2488 used to set the format for the output file. *Note BFD::. 2489 2490 2491File: ld.info, Node: REGION_ALIAS, Next: Miscellaneous Commands, Prev: Format Commands, Up: Simple Commands 2492 24933.4.4 Assign alias names to memory regions 2494------------------------------------------ 2495 2496Alias names can be added to existing memory regions created with the 2497*Note MEMORY:: command. Each name corresponds to at most one memory 2498region. 2499 2500 REGION_ALIAS(ALIAS, REGION) 2501 2502 The `REGION_ALIAS' function creates an alias name ALIAS for the 2503memory region REGION. This allows a flexible mapping of output sections 2504to memory regions. An example follows. 2505 2506 Suppose we have an application for embedded systems which come with 2507various memory storage devices. All have a general purpose, volatile 2508memory `RAM' that allows code execution or data storage. Some may have 2509a read-only, non-volatile memory `ROM' that allows code execution and 2510read-only data access. The last variant is a read-only, non-volatile 2511memory `ROM2' with read-only data access and no code execution 2512capability. We have four output sections: 2513 2514 * `.text' program code; 2515 2516 * `.rodata' read-only data; 2517 2518 * `.data' read-write initialized data; 2519 2520 * `.bss' read-write zero initialized data. 2521 2522 The goal is to provide a linker command file that contains a system 2523independent part defining the output sections and a system dependent 2524part mapping the output sections to the memory regions available on the 2525system. Our embedded systems come with three different memory setups 2526`A', `B' and `C': 2527Section Variant A Variant B Variant C 2528.text RAM ROM ROM 2529.rodata RAM ROM ROM2 2530.data RAM RAM/ROM RAM/ROM2 2531.bss RAM RAM RAM 2532 The notation `RAM/ROM' or `RAM/ROM2' means that this section is 2533loaded into region `ROM' or `ROM2' respectively. Please note that the 2534load address of the `.data' section starts in all three variants at the 2535end of the `.rodata' section. 2536 2537 The base linker script that deals with the output sections follows. 2538It includes the system dependent `linkcmds.memory' file that describes 2539the memory layout: 2540 INCLUDE linkcmds.memory 2541 2542 SECTIONS 2543 { 2544 .text : 2545 { 2546 *(.text) 2547 } > REGION_TEXT 2548 .rodata : 2549 { 2550 *(.rodata) 2551 rodata_end = .; 2552 } > REGION_RODATA 2553 .data : AT (rodata_end) 2554 { 2555 data_start = .; 2556 *(.data) 2557 } > REGION_DATA 2558 data_size = SIZEOF(.data); 2559 data_load_start = LOADADDR(.data); 2560 .bss : 2561 { 2562 *(.bss) 2563 } > REGION_BSS 2564 } 2565 2566 Now we need three different `linkcmds.memory' files to define memory 2567regions and alias names. The content of `linkcmds.memory' for the three 2568variants `A', `B' and `C': 2569`A' 2570 Here everything goes into the `RAM'. 2571 MEMORY 2572 { 2573 RAM : ORIGIN = 0, LENGTH = 4M 2574 } 2575 2576 REGION_ALIAS("REGION_TEXT", RAM); 2577 REGION_ALIAS("REGION_RODATA", RAM); 2578 REGION_ALIAS("REGION_DATA", RAM); 2579 REGION_ALIAS("REGION_BSS", RAM); 2580 2581`B' 2582 Program code and read-only data go into the `ROM'. Read-write 2583 data goes into the `RAM'. An image of the initialized data is 2584 loaded into the `ROM' and will be copied during system start into 2585 the `RAM'. 2586 MEMORY 2587 { 2588 ROM : ORIGIN = 0, LENGTH = 3M 2589 RAM : ORIGIN = 0x10000000, LENGTH = 1M 2590 } 2591 2592 REGION_ALIAS("REGION_TEXT", ROM); 2593 REGION_ALIAS("REGION_RODATA", ROM); 2594 REGION_ALIAS("REGION_DATA", RAM); 2595 REGION_ALIAS("REGION_BSS", RAM); 2596 2597`C' 2598 Program code goes into the `ROM'. Read-only data goes into the 2599 `ROM2'. Read-write data goes into the `RAM'. An image of the 2600 initialized data is loaded into the `ROM2' and will be copied 2601 during system start into the `RAM'. 2602 MEMORY 2603 { 2604 ROM : ORIGIN = 0, LENGTH = 2M 2605 ROM2 : ORIGIN = 0x10000000, LENGTH = 1M 2606 RAM : ORIGIN = 0x20000000, LENGTH = 1M 2607 } 2608 2609 REGION_ALIAS("REGION_TEXT", ROM); 2610 REGION_ALIAS("REGION_RODATA", ROM2); 2611 REGION_ALIAS("REGION_DATA", RAM); 2612 REGION_ALIAS("REGION_BSS", RAM); 2613 2614 It is possible to write a common system initialization routine to 2615copy the `.data' section from `ROM' or `ROM2' into the `RAM' if 2616necessary: 2617 #include <string.h> 2618 2619 extern char data_start []; 2620 extern char data_size []; 2621 extern char data_load_start []; 2622 2623 void copy_data(void) 2624 { 2625 if (data_start != data_load_start) 2626 { 2627 memcpy(data_start, data_load_start, (size_t) data_size); 2628 } 2629 } 2630 2631 2632File: ld.info, Node: Miscellaneous Commands, Prev: REGION_ALIAS, Up: Simple Commands 2633 26343.4.5 Other Linker Script Commands 2635---------------------------------- 2636 2637There are a few other linker scripts commands. 2638 2639`ASSERT(EXP, MESSAGE)' 2640 Ensure that EXP is non-zero. If it is zero, then exit the linker 2641 with an error code, and print MESSAGE. 2642 2643`EXTERN(SYMBOL SYMBOL ...)' 2644 Force SYMBOL to be entered in the output file as an undefined 2645 symbol. Doing this may, for example, trigger linking of additional 2646 modules from standard libraries. You may list several SYMBOLs for 2647 each `EXTERN', and you may use `EXTERN' multiple times. This 2648 command has the same effect as the `-u' command-line option. 2649 2650`FORCE_COMMON_ALLOCATION' 2651 This command has the same effect as the `-d' command-line option: 2652 to make `ld' assign space to common symbols even if a relocatable 2653 output file is specified (`-r'). 2654 2655`INHIBIT_COMMON_ALLOCATION' 2656 This command has the same effect as the `--no-define-common' 2657 command-line option: to make `ld' omit the assignment of addresses 2658 to common symbols even for a non-relocatable output file. 2659 2660`INSERT [ AFTER | BEFORE ] OUTPUT_SECTION' 2661 This command is typically used in a script specified by `-T' to 2662 augment the default `SECTIONS' with, for example, overlays. It 2663 inserts all prior linker script statements after (or before) 2664 OUTPUT_SECTION, and also causes `-T' to not override the default 2665 linker script. The exact insertion point is as for orphan 2666 sections. *Note Location Counter::. The insertion happens after 2667 the linker has mapped input sections to output sections. Prior to 2668 the insertion, since `-T' scripts are parsed before the default 2669 linker script, statements in the `-T' script occur before the 2670 default linker script statements in the internal linker 2671 representation of the script. In particular, input section 2672 assignments will be made to `-T' output sections before those in 2673 the default script. Here is an example of how a `-T' script using 2674 `INSERT' might look: 2675 2676 SECTIONS 2677 { 2678 OVERLAY : 2679 { 2680 .ov1 { ov1*(.text) } 2681 .ov2 { ov2*(.text) } 2682 } 2683 } 2684 INSERT AFTER .text; 2685 2686`NOCROSSREFS(SECTION SECTION ...)' 2687 This command may be used to tell `ld' to issue an error about any 2688 references among certain output sections. 2689 2690 In certain types of programs, particularly on embedded systems when 2691 using overlays, when one section is loaded into memory, another 2692 section will not be. Any direct references between the two 2693 sections would be errors. For example, it would be an error if 2694 code in one section called a function defined in the other section. 2695 2696 The `NOCROSSREFS' command takes a list of output section names. If 2697 `ld' detects any cross references between the sections, it reports 2698 an error and returns a non-zero exit status. Note that the 2699 `NOCROSSREFS' command uses output section names, not input section 2700 names. 2701 2702`OUTPUT_ARCH(BFDARCH)' 2703 Specify a particular output machine architecture. The argument is 2704 one of the names used by the BFD library (*note BFD::). You can 2705 see the architecture of an object file by using the `objdump' 2706 program with the `-f' option. 2707 2708`LD_FEATURE(STRING)' 2709 This command may be used to modify `ld' behavior. If STRING is 2710 `"SANE_EXPR"' then absolute symbols and numbers in a script are 2711 simply treated as numbers everywhere. *Note Expression Section::. 2712 2713 2714File: ld.info, Node: Assignments, Next: SECTIONS, Prev: Simple Commands, Up: Scripts 2715 27163.5 Assigning Values to Symbols 2717=============================== 2718 2719You may assign a value to a symbol in a linker script. This will define 2720the symbol and place it into the symbol table with a global scope. 2721 2722* Menu: 2723 2724* Simple Assignments:: Simple Assignments 2725* PROVIDE:: PROVIDE 2726* PROVIDE_HIDDEN:: PROVIDE_HIDDEN 2727* Source Code Reference:: How to use a linker script defined symbol in source code 2728 2729 2730File: ld.info, Node: Simple Assignments, Next: PROVIDE, Up: Assignments 2731 27323.5.1 Simple Assignments 2733------------------------ 2734 2735You may assign to a symbol using any of the C assignment operators: 2736 2737`SYMBOL = EXPRESSION ;' 2738`SYMBOL += EXPRESSION ;' 2739`SYMBOL -= EXPRESSION ;' 2740`SYMBOL *= EXPRESSION ;' 2741`SYMBOL /= EXPRESSION ;' 2742`SYMBOL <<= EXPRESSION ;' 2743`SYMBOL >>= EXPRESSION ;' 2744`SYMBOL &= EXPRESSION ;' 2745`SYMBOL |= EXPRESSION ;' 2746 2747 The first case will define SYMBOL to the value of EXPRESSION. In 2748the other cases, SYMBOL must already be defined, and the value will be 2749adjusted accordingly. 2750 2751 The special symbol name `.' indicates the location counter. You may 2752only use this within a `SECTIONS' command. *Note Location Counter::. 2753 2754 The semicolon after EXPRESSION is required. 2755 2756 Expressions are defined below; see *Note Expressions::. 2757 2758 You may write symbol assignments as commands in their own right, or 2759as statements within a `SECTIONS' command, or as part of an output 2760section description in a `SECTIONS' command. 2761 2762 The section of the symbol will be set from the section of the 2763expression; for more information, see *Note Expression Section::. 2764 2765 Here is an example showing the three different places that symbol 2766assignments may be used: 2767 2768 floating_point = 0; 2769 SECTIONS 2770 { 2771 .text : 2772 { 2773 *(.text) 2774 _etext = .; 2775 } 2776 _bdata = (. + 3) & ~ 3; 2777 .data : { *(.data) } 2778 } 2779 In this example, the symbol `floating_point' will be defined as 2780zero. The symbol `_etext' will be defined as the address following the 2781last `.text' input section. The symbol `_bdata' will be defined as the 2782address following the `.text' output section aligned upward to a 4 byte 2783boundary. 2784 2785 2786File: ld.info, Node: PROVIDE, Next: PROVIDE_HIDDEN, Prev: Simple Assignments, Up: Assignments 2787 27883.5.2 PROVIDE 2789------------- 2790 2791In some cases, it is desirable for a linker script to define a symbol 2792only if it is referenced and is not defined by any object included in 2793the link. For example, traditional linkers defined the symbol `etext'. 2794However, ANSI C requires that the user be able to use `etext' as a 2795function name without encountering an error. The `PROVIDE' keyword may 2796be used to define a symbol, such as `etext', only if it is referenced 2797but not defined. The syntax is `PROVIDE(SYMBOL = EXPRESSION)'. 2798 2799 Here is an example of using `PROVIDE' to define `etext': 2800 SECTIONS 2801 { 2802 .text : 2803 { 2804 *(.text) 2805 _etext = .; 2806 PROVIDE(etext = .); 2807 } 2808 } 2809 2810 In this example, if the program defines `_etext' (with a leading 2811underscore), the linker will give a multiple definition error. If, on 2812the other hand, the program defines `etext' (with no leading 2813underscore), the linker will silently use the definition in the program. 2814If the program references `etext' but does not define it, the linker 2815will use the definition in the linker script. 2816 2817 2818File: ld.info, Node: PROVIDE_HIDDEN, Next: Source Code Reference, Prev: PROVIDE, Up: Assignments 2819 28203.5.3 PROVIDE_HIDDEN 2821-------------------- 2822 2823Similar to `PROVIDE'. For ELF targeted ports, the symbol will be 2824hidden and won't be exported. 2825 2826 2827File: ld.info, Node: Source Code Reference, Prev: PROVIDE_HIDDEN, Up: Assignments 2828 28293.5.4 Source Code Reference 2830--------------------------- 2831 2832Accessing a linker script defined variable from source code is not 2833intuitive. In particular a linker script symbol is not equivalent to a 2834variable declaration in a high level language, it is instead a symbol 2835that does not have a value. 2836 2837 Before going further, it is important to note that compilers often 2838transform names in the source code into different names when they are 2839stored in the symbol table. For example, Fortran compilers commonly 2840prepend or append an underscore, and C++ performs extensive `name 2841mangling'. Therefore there might be a discrepancy between the name of 2842a variable as it is used in source code and the name of the same 2843variable as it is defined in a linker script. For example in C a 2844linker script variable might be referred to as: 2845 2846 extern int foo; 2847 2848 But in the linker script it might be defined as: 2849 2850 _foo = 1000; 2851 2852 In the remaining examples however it is assumed that no name 2853transformation has taken place. 2854 2855 When a symbol is declared in a high level language such as C, two 2856things happen. The first is that the compiler reserves enough space in 2857the program's memory to hold the _value_ of the symbol. The second is 2858that the compiler creates an entry in the program's symbol table which 2859holds the symbol's _address_. ie the symbol table contains the address 2860of the block of memory holding the symbol's value. So for example the 2861following C declaration, at file scope: 2862 2863 int foo = 1000; 2864 2865 creates a entry called `foo' in the symbol table. This entry holds 2866the address of an `int' sized block of memory where the number 1000 is 2867initially stored. 2868 2869 When a program references a symbol the compiler generates code that 2870first accesses the symbol table to find the address of the symbol's 2871memory block and then code to read the value from that memory block. 2872So: 2873 2874 foo = 1; 2875 2876 looks up the symbol `foo' in the symbol table, gets the address 2877associated with this symbol and then writes the value 1 into that 2878address. Whereas: 2879 2880 int * a = & foo; 2881 2882 looks up the symbol `foo' in the symbol table, gets it address and 2883then copies this address into the block of memory associated with the 2884variable `a'. 2885 2886 Linker scripts symbol declarations, by contrast, create an entry in 2887the symbol table but do not assign any memory to them. Thus they are 2888an address without a value. So for example the linker script 2889definition: 2890 2891 foo = 1000; 2892 2893 creates an entry in the symbol table called `foo' which holds the 2894address of memory location 1000, but nothing special is stored at 2895address 1000. This means that you cannot access the _value_ of a 2896linker script defined symbol - it has no value - all you can do is 2897access the _address_ of a linker script defined symbol. 2898 2899 Hence when you are using a linker script defined symbol in source 2900code you should always take the address of the symbol, and never 2901attempt to use its value. For example suppose you want to copy the 2902contents of a section of memory called .ROM into a section called 2903.FLASH and the linker script contains these declarations: 2904 2905 start_of_ROM = .ROM; 2906 end_of_ROM = .ROM + sizeof (.ROM) - 1; 2907 start_of_FLASH = .FLASH; 2908 2909 Then the C source code to perform the copy would be: 2910 2911 extern char start_of_ROM, end_of_ROM, start_of_FLASH; 2912 2913 memcpy (& start_of_FLASH, & start_of_ROM, & end_of_ROM - & start_of_ROM); 2914 2915 Note the use of the `&' operators. These are correct. 2916 2917 2918File: ld.info, Node: SECTIONS, Next: MEMORY, Prev: Assignments, Up: Scripts 2919 29203.6 SECTIONS Command 2921==================== 2922 2923The `SECTIONS' command tells the linker how to map input sections into 2924output sections, and how to place the output sections in memory. 2925 2926 The format of the `SECTIONS' command is: 2927 SECTIONS 2928 { 2929 SECTIONS-COMMAND 2930 SECTIONS-COMMAND 2931 ... 2932 } 2933 2934 Each SECTIONS-COMMAND may of be one of the following: 2935 2936 * an `ENTRY' command (*note Entry command: Entry Point.) 2937 2938 * a symbol assignment (*note Assignments::) 2939 2940 * an output section description 2941 2942 * an overlay description 2943 2944 The `ENTRY' command and symbol assignments are permitted inside the 2945`SECTIONS' command for convenience in using the location counter in 2946those commands. This can also make the linker script easier to 2947understand because you can use those commands at meaningful points in 2948the layout of the output file. 2949 2950 Output section descriptions and overlay descriptions are described 2951below. 2952 2953 If you do not use a `SECTIONS' command in your linker script, the 2954linker will place each input section into an identically named output 2955section in the order that the sections are first encountered in the 2956input files. If all input sections are present in the first file, for 2957example, the order of sections in the output file will match the order 2958in the first input file. The first section will be at address zero. 2959 2960* Menu: 2961 2962* Output Section Description:: Output section description 2963* Output Section Name:: Output section name 2964* Output Section Address:: Output section address 2965* Input Section:: Input section description 2966* Output Section Data:: Output section data 2967* Output Section Keywords:: Output section keywords 2968* Output Section Discarding:: Output section discarding 2969* Output Section Attributes:: Output section attributes 2970* Overlay Description:: Overlay description 2971 2972 2973File: ld.info, Node: Output Section Description, Next: Output Section Name, Up: SECTIONS 2974 29753.6.1 Output Section Description 2976-------------------------------- 2977 2978The full description of an output section looks like this: 2979 SECTION [ADDRESS] [(TYPE)] : 2980 [AT(LMA)] 2981 [ALIGN(SECTION_ALIGN)] 2982 [SUBALIGN(SUBSECTION_ALIGN)] 2983 [CONSTRAINT] 2984 { 2985 OUTPUT-SECTION-COMMAND 2986 OUTPUT-SECTION-COMMAND 2987 ... 2988 } [>REGION] [AT>LMA_REGION] [:PHDR :PHDR ...] [=FILLEXP] 2989 2990 Most output sections do not use most of the optional section 2991attributes. 2992 2993 The whitespace around SECTION is required, so that the section name 2994is unambiguous. The colon and the curly braces are also required. The 2995line breaks and other white space are optional. 2996 2997 Each OUTPUT-SECTION-COMMAND may be one of the following: 2998 2999 * a symbol assignment (*note Assignments::) 3000 3001 * an input section description (*note Input Section::) 3002 3003 * data values to include directly (*note Output Section Data::) 3004 3005 * a special output section keyword (*note Output Section Keywords::) 3006 3007 3008File: ld.info, Node: Output Section Name, Next: Output Section Address, Prev: Output Section Description, Up: SECTIONS 3009 30103.6.2 Output Section Name 3011------------------------- 3012 3013The name of the output section is SECTION. SECTION must meet the 3014constraints of your output format. In formats which only support a 3015limited number of sections, such as `a.out', the name must be one of 3016the names supported by the format (`a.out', for example, allows only 3017`.text', `.data' or `.bss'). If the output format supports any number 3018of sections, but with numbers and not names (as is the case for Oasys), 3019the name should be supplied as a quoted numeric string. A section name 3020may consist of any sequence of characters, but a name which contains 3021any unusual characters such as commas must be quoted. 3022 3023 The output section name `/DISCARD/' is special; *Note Output Section 3024Discarding::. 3025 3026 3027File: ld.info, Node: Output Section Address, Next: Input Section, Prev: Output Section Name, Up: SECTIONS 3028 30293.6.3 Output Section Address 3030---------------------------- 3031 3032The ADDRESS is an expression for the VMA (the virtual memory address) 3033of the output section. This address is optional, but if it is provided 3034then the output address will be set exactly as specified. 3035 3036 If the output address is not specified then one will be chosen for 3037the section, based on the heuristic below. This address will be 3038adjusted to fit the alignment requirement of the output section. The 3039alignment requirement is the strictest alignment of any input section 3040contained within the output section. 3041 3042 The output section address heuristic is as follows: 3043 3044 * If an output memory REGION is set for the section then it is added 3045 to this region and its address will be the next free address in 3046 that region. 3047 3048 * If the MEMORY command has been used to create a list of memory 3049 regions then the first region which has attributes compatible with 3050 the section is selected to contain it. The section's output 3051 address will be the next free address in that region; *Note 3052 MEMORY::. 3053 3054 * If no memory regions were specified, or none match the section then 3055 the output address will be based on the current value of the 3056 location counter. 3057 3058For example: 3059 3060 .text . : { *(.text) } 3061 3062and 3063 3064 .text : { *(.text) } 3065 3066are subtly different. The first will set the address of the `.text' 3067output section to the current value of the location counter. The 3068second will set it to the current value of the location counter aligned 3069to the strictest alignment of any of the `.text' input sections. 3070 3071 The ADDRESS may be an arbitrary expression; *Note Expressions::. 3072For example, if you want to align the section on a 0x10 byte boundary, 3073so that the lowest four bits of the section address are zero, you could 3074do something like this: 3075 .text ALIGN(0x10) : { *(.text) } 3076 This works because `ALIGN' returns the current location counter 3077aligned upward to the specified value. 3078 3079 Specifying ADDRESS for a section will change the value of the 3080location counter, provided that the section is non-empty. (Empty 3081sections are ignored). 3082 3083 3084File: ld.info, Node: Input Section, Next: Output Section Data, Prev: Output Section Address, Up: SECTIONS 3085 30863.6.4 Input Section Description 3087------------------------------- 3088 3089The most common output section command is an input section description. 3090 3091 The input section description is the most basic linker script 3092operation. You use output sections to tell the linker how to lay out 3093your program in memory. You use input section descriptions to tell the 3094linker how to map the input files into your memory layout. 3095 3096* Menu: 3097 3098* Input Section Basics:: Input section basics 3099* Input Section Wildcards:: Input section wildcard patterns 3100* Input Section Common:: Input section for common symbols 3101* Input Section Keep:: Input section and garbage collection 3102* Input Section Example:: Input section example 3103 3104 3105File: ld.info, Node: Input Section Basics, Next: Input Section Wildcards, Up: Input Section 3106 31073.6.4.1 Input Section Basics 3108............................ 3109 3110An input section description consists of a file name optionally followed 3111by a list of section names in parentheses. 3112 3113 The file name and the section name may be wildcard patterns, which we 3114describe further below (*note Input Section Wildcards::). 3115 3116 The most common input section description is to include all input 3117sections with a particular name in the output section. For example, to 3118include all input `.text' sections, you would write: 3119 *(.text) 3120 Here the `*' is a wildcard which matches any file name. To exclude 3121a list of files from matching the file name wildcard, EXCLUDE_FILE may 3122be used to match all files except the ones specified in the 3123EXCLUDE_FILE list. For example: 3124 *(EXCLUDE_FILE (*crtend.o *otherfile.o) .ctors) 3125 will cause all .ctors sections from all files except `crtend.o' and 3126`otherfile.o' to be included. 3127 3128 There are two ways to include more than one section: 3129 *(.text .rdata) 3130 *(.text) *(.rdata) 3131 The difference between these is the order in which the `.text' and 3132`.rdata' input sections will appear in the output section. In the 3133first example, they will be intermingled, appearing in the same order as 3134they are found in the linker input. In the second example, all `.text' 3135input sections will appear first, followed by all `.rdata' input 3136sections. 3137 3138 You can specify a file name to include sections from a particular 3139file. You would do this if one or more of your files contain special 3140data that needs to be at a particular location in memory. For example: 3141 data.o(.data) 3142 3143 You can also specify files within archives by writing a pattern 3144matching the archive, a colon, then the pattern matching the file, with 3145no whitespace around the colon. 3146 3147`archive:file' 3148 matches file within archive 3149 3150`archive:' 3151 matches the whole archive 3152 3153`:file' 3154 matches file but not one in an archive 3155 3156 Either one or both of `archive' and `file' can contain shell 3157wildcards. On DOS based file systems, the linker will assume that a 3158single letter followed by a colon is a drive specifier, so `c:myfile.o' 3159is a simple file specification, not `myfile.o' within an archive called 3160`c'. `archive:file' filespecs may also be used within an 3161`EXCLUDE_FILE' list, but may not appear in other linker script 3162contexts. For instance, you cannot extract a file from an archive by 3163using `archive:file' in an `INPUT' command. 3164 3165 If you use a file name without a list of sections, then all sections 3166in the input file will be included in the output section. This is not 3167commonly done, but it may by useful on occasion. For example: 3168 data.o 3169 3170 When you use a file name which is not an `archive:file' specifier 3171and does not contain any wild card characters, the linker will first 3172see if you also specified the file name on the linker command line or 3173in an `INPUT' command. If you did not, the linker will attempt to open 3174the file as an input file, as though it appeared on the command line. 3175Note that this differs from an `INPUT' command, because the linker will 3176not search for the file in the archive search path. 3177 3178 3179File: ld.info, Node: Input Section Wildcards, Next: Input Section Common, Prev: Input Section Basics, Up: Input Section 3180 31813.6.4.2 Input Section Wildcard Patterns 3182....................................... 3183 3184In an input section description, either the file name or the section 3185name or both may be wildcard patterns. 3186 3187 The file name of `*' seen in many examples is a simple wildcard 3188pattern for the file name. 3189 3190 The wildcard patterns are like those used by the Unix shell. 3191 3192`*' 3193 matches any number of characters 3194 3195`?' 3196 matches any single character 3197 3198`[CHARS]' 3199 matches a single instance of any of the CHARS; the `-' character 3200 may be used to specify a range of characters, as in `[a-z]' to 3201 match any lower case letter 3202 3203`\' 3204 quotes the following character 3205 3206 When a file name is matched with a wildcard, the wildcard characters 3207will not match a `/' character (used to separate directory names on 3208Unix). A pattern consisting of a single `*' character is an exception; 3209it will always match any file name, whether it contains a `/' or not. 3210In a section name, the wildcard characters will match a `/' character. 3211 3212 File name wildcard patterns only match files which are explicitly 3213specified on the command line or in an `INPUT' command. The linker 3214does not search directories to expand wildcards. 3215 3216 If a file name matches more than one wildcard pattern, or if a file 3217name appears explicitly and is also matched by a wildcard pattern, the 3218linker will use the first match in the linker script. For example, this 3219sequence of input section descriptions is probably in error, because the 3220`data.o' rule will not be used: 3221 .data : { *(.data) } 3222 .data1 : { data.o(.data) } 3223 3224 Normally, the linker will place files and sections matched by 3225wildcards in the order in which they are seen during the link. You can 3226change this by using the `SORT_BY_NAME' keyword, which appears before a 3227wildcard pattern in parentheses (e.g., `SORT_BY_NAME(.text*)'). When 3228the `SORT_BY_NAME' keyword is used, the linker will sort the files or 3229sections into ascending order by name before placing them in the output 3230file. 3231 3232 `SORT_BY_ALIGNMENT' is very similar to `SORT_BY_NAME'. The 3233difference is `SORT_BY_ALIGNMENT' will sort sections into ascending 3234order by alignment before placing them in the output file. 3235 3236 `SORT' is an alias for `SORT_BY_NAME'. 3237 3238 When there are nested section sorting commands in linker script, 3239there can be at most 1 level of nesting for section sorting commands. 3240 3241 1. `SORT_BY_NAME' (`SORT_BY_ALIGNMENT' (wildcard section pattern)). 3242 It will sort the input sections by name first, then by alignment 3243 if 2 sections have the same name. 3244 3245 2. `SORT_BY_ALIGNMENT' (`SORT_BY_NAME' (wildcard section pattern)). 3246 It will sort the input sections by alignment first, then by name 3247 if 2 sections have the same alignment. 3248 3249 3. `SORT_BY_NAME' (`SORT_BY_NAME' (wildcard section pattern)) is 3250 treated the same as `SORT_BY_NAME' (wildcard section pattern). 3251 3252 4. `SORT_BY_ALIGNMENT' (`SORT_BY_ALIGNMENT' (wildcard section 3253 pattern)) is treated the same as `SORT_BY_ALIGNMENT' (wildcard 3254 section pattern). 3255 3256 5. All other nested section sorting commands are invalid. 3257 3258 When both command line section sorting option and linker script 3259section sorting command are used, section sorting command always takes 3260precedence over the command line option. 3261 3262 If the section sorting command in linker script isn't nested, the 3263command line option will make the section sorting command to be treated 3264as nested sorting command. 3265 3266 1. `SORT_BY_NAME' (wildcard section pattern ) with `--sort-sections 3267 alignment' is equivalent to `SORT_BY_NAME' (`SORT_BY_ALIGNMENT' 3268 (wildcard section pattern)). 3269 3270 2. `SORT_BY_ALIGNMENT' (wildcard section pattern) with 3271 `--sort-section name' is equivalent to `SORT_BY_ALIGNMENT' 3272 (`SORT_BY_NAME' (wildcard section pattern)). 3273 3274 If the section sorting command in linker script is nested, the 3275command line option will be ignored. 3276 3277 If you ever get confused about where input sections are going, use 3278the `-M' linker option to generate a map file. The map file shows 3279precisely how input sections are mapped to output sections. 3280 3281 This example shows how wildcard patterns might be used to partition 3282files. This linker script directs the linker to place all `.text' 3283sections in `.text' and all `.bss' sections in `.bss'. The linker will 3284place the `.data' section from all files beginning with an upper case 3285character in `.DATA'; for all other files, the linker will place the 3286`.data' section in `.data'. 3287 SECTIONS { 3288 .text : { *(.text) } 3289 .DATA : { [A-Z]*(.data) } 3290 .data : { *(.data) } 3291 .bss : { *(.bss) } 3292 } 3293 3294 3295File: ld.info, Node: Input Section Common, Next: Input Section Keep, Prev: Input Section Wildcards, Up: Input Section 3296 32973.6.4.3 Input Section for Common Symbols 3298........................................ 3299 3300A special notation is needed for common symbols, because in many object 3301file formats common symbols do not have a particular input section. The 3302linker treats common symbols as though they are in an input section 3303named `COMMON'. 3304 3305 You may use file names with the `COMMON' section just as with any 3306other input sections. You can use this to place common symbols from a 3307particular input file in one section while common symbols from other 3308input files are placed in another section. 3309 3310 In most cases, common symbols in input files will be placed in the 3311`.bss' section in the output file. For example: 3312 .bss { *(.bss) *(COMMON) } 3313 3314 Some object file formats have more than one type of common symbol. 3315For example, the MIPS ELF object file format distinguishes standard 3316common symbols and small common symbols. In this case, the linker will 3317use a different special section name for other types of common symbols. 3318In the case of MIPS ELF, the linker uses `COMMON' for standard common 3319symbols and `.scommon' for small common symbols. This permits you to 3320map the different types of common symbols into memory at different 3321locations. 3322 3323 You will sometimes see `[COMMON]' in old linker scripts. This 3324notation is now considered obsolete. It is equivalent to `*(COMMON)'. 3325 3326 3327File: ld.info, Node: Input Section Keep, Next: Input Section Example, Prev: Input Section Common, Up: Input Section 3328 33293.6.4.4 Input Section and Garbage Collection 3330............................................ 3331 3332When link-time garbage collection is in use (`--gc-sections'), it is 3333often useful to mark sections that should not be eliminated. This is 3334accomplished by surrounding an input section's wildcard entry with 3335`KEEP()', as in `KEEP(*(.init))' or `KEEP(SORT_BY_NAME(*)(.ctors))'. 3336 3337 3338File: ld.info, Node: Input Section Example, Prev: Input Section Keep, Up: Input Section 3339 33403.6.4.5 Input Section Example 3341............................. 3342 3343The following example is a complete linker script. It tells the linker 3344to read all of the sections from file `all.o' and place them at the 3345start of output section `outputa' which starts at location `0x10000'. 3346All of section `.input1' from file `foo.o' follows immediately, in the 3347same output section. All of section `.input2' from `foo.o' goes into 3348output section `outputb', followed by section `.input1' from `foo1.o'. 3349All of the remaining `.input1' and `.input2' sections from any files 3350are written to output section `outputc'. 3351 3352 SECTIONS { 3353 outputa 0x10000 : 3354 { 3355 all.o 3356 foo.o (.input1) 3357 } 3358 outputb : 3359 { 3360 foo.o (.input2) 3361 foo1.o (.input1) 3362 } 3363 outputc : 3364 { 3365 *(.input1) 3366 *(.input2) 3367 } 3368 } 3369 3370 3371File: ld.info, Node: Output Section Data, Next: Output Section Keywords, Prev: Input Section, Up: SECTIONS 3372 33733.6.5 Output Section Data 3374------------------------- 3375 3376You can include explicit bytes of data in an output section by using 3377`BYTE', `SHORT', `LONG', `QUAD', or `SQUAD' as an output section 3378command. Each keyword is followed by an expression in parentheses 3379providing the value to store (*note Expressions::). The value of the 3380expression is stored at the current value of the location counter. 3381 3382 The `BYTE', `SHORT', `LONG', and `QUAD' commands store one, two, 3383four, and eight bytes (respectively). After storing the bytes, the 3384location counter is incremented by the number of bytes stored. 3385 3386 For example, this will store the byte 1 followed by the four byte 3387value of the symbol `addr': 3388 BYTE(1) 3389 LONG(addr) 3390 3391 When using a 64 bit host or target, `QUAD' and `SQUAD' are the same; 3392they both store an 8 byte, or 64 bit, value. When both host and target 3393are 32 bits, an expression is computed as 32 bits. In this case `QUAD' 3394stores a 32 bit value zero extended to 64 bits, and `SQUAD' stores a 32 3395bit value sign extended to 64 bits. 3396 3397 If the object file format of the output file has an explicit 3398endianness, which is the normal case, the value will be stored in that 3399endianness. When the object file format does not have an explicit 3400endianness, as is true of, for example, S-records, the value will be 3401stored in the endianness of the first input object file. 3402 3403 Note--these commands only work inside a section description and not 3404between them, so the following will produce an error from the linker: 3405 SECTIONS { .text : { *(.text) } LONG(1) .data : { *(.data) } } 3406 whereas this will work: 3407 SECTIONS { .text : { *(.text) ; LONG(1) } .data : { *(.data) } } 3408 3409 You may use the `FILL' command to set the fill pattern for the 3410current section. It is followed by an expression in parentheses. Any 3411otherwise unspecified regions of memory within the section (for example, 3412gaps left due to the required alignment of input sections) are filled 3413with the value of the expression, repeated as necessary. A `FILL' 3414statement covers memory locations after the point at which it occurs in 3415the section definition; by including more than one `FILL' statement, 3416you can have different fill patterns in different parts of an output 3417section. 3418 3419 This example shows how to fill unspecified regions of memory with the 3420value `0x90': 3421 FILL(0x90909090) 3422 3423 The `FILL' command is similar to the `=FILLEXP' output section 3424attribute, but it only affects the part of the section following the 3425`FILL' command, rather than the entire section. If both are used, the 3426`FILL' command takes precedence. *Note Output Section Fill::, for 3427details on the fill expression. 3428 3429 3430File: ld.info, Node: Output Section Keywords, Next: Output Section Discarding, Prev: Output Section Data, Up: SECTIONS 3431 34323.6.6 Output Section Keywords 3433----------------------------- 3434 3435There are a couple of keywords which can appear as output section 3436commands. 3437 3438`CREATE_OBJECT_SYMBOLS' 3439 The command tells the linker to create a symbol for each input 3440 file. The name of each symbol will be the name of the 3441 corresponding input file. The section of each symbol will be the 3442 output section in which the `CREATE_OBJECT_SYMBOLS' command 3443 appears. 3444 3445 This is conventional for the a.out object file format. It is not 3446 normally used for any other object file format. 3447 3448`CONSTRUCTORS' 3449 When linking using the a.out object file format, the linker uses an 3450 unusual set construct to support C++ global constructors and 3451 destructors. When linking object file formats which do not support 3452 arbitrary sections, such as ECOFF and XCOFF, the linker will 3453 automatically recognize C++ global constructors and destructors by 3454 name. For these object file formats, the `CONSTRUCTORS' command 3455 tells the linker to place constructor information in the output 3456 section where the `CONSTRUCTORS' command appears. The 3457 `CONSTRUCTORS' command is ignored for other object file formats. 3458 3459 The symbol `__CTOR_LIST__' marks the start of the global 3460 constructors, and the symbol `__CTOR_END__' marks the end. 3461 Similarly, `__DTOR_LIST__' and `__DTOR_END__' mark the start and 3462 end of the global destructors. The first word in the list is the 3463 number of entries, followed by the address of each constructor or 3464 destructor, followed by a zero word. The compiler must arrange to 3465 actually run the code. For these object file formats GNU C++ 3466 normally calls constructors from a subroutine `__main'; a call to 3467 `__main' is automatically inserted into the startup code for 3468 `main'. GNU C++ normally runs destructors either by using 3469 `atexit', or directly from the function `exit'. 3470 3471 For object file formats such as `COFF' or `ELF' which support 3472 arbitrary section names, GNU C++ will normally arrange to put the 3473 addresses of global constructors and destructors into the `.ctors' 3474 and `.dtors' sections. Placing the following sequence into your 3475 linker script will build the sort of table which the GNU C++ 3476 runtime code expects to see. 3477 3478 __CTOR_LIST__ = .; 3479 LONG((__CTOR_END__ - __CTOR_LIST__) / 4 - 2) 3480 *(.ctors) 3481 LONG(0) 3482 __CTOR_END__ = .; 3483 __DTOR_LIST__ = .; 3484 LONG((__DTOR_END__ - __DTOR_LIST__) / 4 - 2) 3485 *(.dtors) 3486 LONG(0) 3487 __DTOR_END__ = .; 3488 3489 If you are using the GNU C++ support for initialization priority, 3490 which provides some control over the order in which global 3491 constructors are run, you must sort the constructors at link time 3492 to ensure that they are executed in the correct order. When using 3493 the `CONSTRUCTORS' command, use `SORT_BY_NAME(CONSTRUCTORS)' 3494 instead. When using the `.ctors' and `.dtors' sections, use 3495 `*(SORT_BY_NAME(.ctors))' and `*(SORT_BY_NAME(.dtors))' instead of 3496 just `*(.ctors)' and `*(.dtors)'. 3497 3498 Normally the compiler and linker will handle these issues 3499 automatically, and you will not need to concern yourself with 3500 them. However, you may need to consider this if you are using C++ 3501 and writing your own linker scripts. 3502 3503 3504 3505File: ld.info, Node: Output Section Discarding, Next: Output Section Attributes, Prev: Output Section Keywords, Up: SECTIONS 3506 35073.6.7 Output Section Discarding 3508------------------------------- 3509 3510The linker will not create output sections with no contents. This is 3511for convenience when referring to input sections that may or may not be 3512present in any of the input files. For example: 3513 .foo : { *(.foo) } 3514 will only create a `.foo' section in the output file if there is a 3515`.foo' section in at least one input file, and if the input sections 3516are not all empty. Other link script directives that allocate space in 3517an output section will also create the output section. 3518 3519 The linker will ignore address assignments (*note Output Section 3520Address::) on discarded output sections, except when the linker script 3521defines symbols in the output section. In that case the linker will 3522obey the address assignments, possibly advancing dot even though the 3523section is discarded. 3524 3525 The special output section name `/DISCARD/' may be used to discard 3526input sections. Any input sections which are assigned to an output 3527section named `/DISCARD/' are not included in the output file. 3528 3529 3530File: ld.info, Node: Output Section Attributes, Next: Overlay Description, Prev: Output Section Discarding, Up: SECTIONS 3531 35323.6.8 Output Section Attributes 3533------------------------------- 3534 3535We showed above that the full description of an output section looked 3536like this: 3537 3538 SECTION [ADDRESS] [(TYPE)] : 3539 [AT(LMA)] 3540 [ALIGN(SECTION_ALIGN)] 3541 [SUBALIGN(SUBSECTION_ALIGN)] 3542 [CONSTRAINT] 3543 { 3544 OUTPUT-SECTION-COMMAND 3545 OUTPUT-SECTION-COMMAND 3546 ... 3547 } [>REGION] [AT>LMA_REGION] [:PHDR :PHDR ...] [=FILLEXP] 3548 3549 We've already described SECTION, ADDRESS, and 3550OUTPUT-SECTION-COMMAND. In this section we will describe the remaining 3551section attributes. 3552 3553* Menu: 3554 3555* Output Section Type:: Output section type 3556* Output Section LMA:: Output section LMA 3557* Forced Output Alignment:: Forced Output Alignment 3558* Forced Input Alignment:: Forced Input Alignment 3559* Output Section Constraint:: Output section constraint 3560* Output Section Region:: Output section region 3561* Output Section Phdr:: Output section phdr 3562* Output Section Fill:: Output section fill 3563 3564 3565File: ld.info, Node: Output Section Type, Next: Output Section LMA, Up: Output Section Attributes 3566 35673.6.8.1 Output Section Type 3568........................... 3569 3570Each output section may have a type. The type is a keyword in 3571parentheses. The following types are defined: 3572 3573`NOLOAD' 3574 The section should be marked as not loadable, so that it will not 3575 be loaded into memory when the program is run. 3576 3577`DSECT' 3578`COPY' 3579`INFO' 3580`OVERLAY' 3581 These type names are supported for backward compatibility, and are 3582 rarely used. They all have the same effect: the section should be 3583 marked as not allocatable, so that no memory is allocated for the 3584 section when the program is run. 3585 3586 The linker normally sets the attributes of an output section based on 3587the input sections which map into it. You can override this by using 3588the section type. For example, in the script sample below, the `ROM' 3589section is addressed at memory location `0' and does not need to be 3590loaded when the program is run. 3591 SECTIONS { 3592 ROM 0 (NOLOAD) : { ... } 3593 ... 3594 } 3595 3596 3597File: ld.info, Node: Output Section LMA, Next: Forced Output Alignment, Prev: Output Section Type, Up: Output Section Attributes 3598 35993.6.8.2 Output Section LMA 3600.......................... 3601 3602Every section has a virtual address (VMA) and a load address (LMA); see 3603*Note Basic Script Concepts::. The virtual address is specified by the 3604*note Output Section Address:: described earlier. The load address is 3605specified by the `AT' or `AT>' keywords. Specifying a load address is 3606optional. 3607 3608 The `AT' keyword takes an expression as an argument. This specifies 3609the exact load address of the section. The `AT>' keyword takes the 3610name of a memory region as an argument. *Note MEMORY::. The load 3611address of the section is set to the next free address in the region, 3612aligned to the section's alignment requirements. 3613 3614 If neither `AT' nor `AT>' is specified for an allocatable section, 3615the linker will use the following heuristic to determine the load 3616address: 3617 3618 * If the section has a specific VMA address, then this is used as 3619 the LMA address as well. 3620 3621 * If the section is not allocatable then its LMA is set to its VMA. 3622 3623 * Otherwise if a memory region can be found that is compatible with 3624 the current section, and this region contains at least one 3625 section, then the LMA is set so the difference between the VMA and 3626 LMA is the same as the difference between the VMA and LMA of the 3627 last section in the located region. 3628 3629 * If no memory regions have been declared then a default region that 3630 covers the entire address space is used in the previous step. 3631 3632 * If no suitable region could be found, or there was no previous 3633 section then the LMA is set equal to the VMA. 3634 3635 This feature is designed to make it easy to build a ROM image. For 3636example, the following linker script creates three output sections: one 3637called `.text', which starts at `0x1000', one called `.mdata', which is 3638loaded at the end of the `.text' section even though its VMA is 3639`0x2000', and one called `.bss' to hold uninitialized data at address 3640`0x3000'. The symbol `_data' is defined with the value `0x2000', which 3641shows that the location counter holds the VMA value, not the LMA value. 3642 3643 SECTIONS 3644 { 3645 .text 0x1000 : { *(.text) _etext = . ; } 3646 .mdata 0x2000 : 3647 AT ( ADDR (.text) + SIZEOF (.text) ) 3648 { _data = . ; *(.data); _edata = . ; } 3649 .bss 0x3000 : 3650 { _bstart = . ; *(.bss) *(COMMON) ; _bend = . ;} 3651 } 3652 3653 The run-time initialization code for use with a program generated 3654with this linker script would include something like the following, to 3655copy the initialized data from the ROM image to its runtime address. 3656Notice how this code takes advantage of the symbols defined by the 3657linker script. 3658 3659 extern char _etext, _data, _edata, _bstart, _bend; 3660 char *src = &_etext; 3661 char *dst = &_data; 3662 3663 /* ROM has data at end of text; copy it. */ 3664 while (dst < &_edata) 3665 *dst++ = *src++; 3666 3667 /* Zero bss. */ 3668 for (dst = &_bstart; dst< &_bend; dst++) 3669 *dst = 0; 3670 3671 3672File: ld.info, Node: Forced Output Alignment, Next: Forced Input Alignment, Prev: Output Section LMA, Up: Output Section Attributes 3673 36743.6.8.3 Forced Output Alignment 3675............................... 3676 3677You can increase an output section's alignment by using ALIGN. 3678 3679 3680File: ld.info, Node: Forced Input Alignment, Next: Output Section Constraint, Prev: Forced Output Alignment, Up: Output Section Attributes 3681 36823.6.8.4 Forced Input Alignment 3683.............................. 3684 3685You can force input section alignment within an output section by using 3686SUBALIGN. The value specified overrides any alignment given by input 3687sections, whether larger or smaller. 3688 3689 3690File: ld.info, Node: Output Section Constraint, Next: Output Section Region, Prev: Forced Input Alignment, Up: Output Section Attributes 3691 36923.6.8.5 Output Section Constraint 3693................................. 3694 3695You can specify that an output section should only be created if all of 3696its input sections are read-only or all of its input sections are 3697read-write by using the keyword `ONLY_IF_RO' and `ONLY_IF_RW' 3698respectively. 3699 3700 3701File: ld.info, Node: Output Section Region, Next: Output Section Phdr, Prev: Output Section Constraint, Up: Output Section Attributes 3702 37033.6.8.6 Output Section Region 3704............................. 3705 3706You can assign a section to a previously defined region of memory by 3707using `>REGION'. *Note MEMORY::. 3708 3709 Here is a simple example: 3710 MEMORY { rom : ORIGIN = 0x1000, LENGTH = 0x1000 } 3711 SECTIONS { ROM : { *(.text) } >rom } 3712 3713 3714File: ld.info, Node: Output Section Phdr, Next: Output Section Fill, Prev: Output Section Region, Up: Output Section Attributes 3715 37163.6.8.7 Output Section Phdr 3717........................... 3718 3719You can assign a section to a previously defined program segment by 3720using `:PHDR'. *Note PHDRS::. If a section is assigned to one or more 3721segments, then all subsequent allocated sections will be assigned to 3722those segments as well, unless they use an explicitly `:PHDR' modifier. 3723You can use `:NONE' to tell the linker to not put the section in any 3724segment at all. 3725 3726 Here is a simple example: 3727 PHDRS { text PT_LOAD ; } 3728 SECTIONS { .text : { *(.text) } :text } 3729 3730 3731File: ld.info, Node: Output Section Fill, Prev: Output Section Phdr, Up: Output Section Attributes 3732 37333.6.8.8 Output Section Fill 3734........................... 3735 3736You can set the fill pattern for an entire section by using `=FILLEXP'. 3737FILLEXP is an expression (*note Expressions::). Any otherwise 3738unspecified regions of memory within the output section (for example, 3739gaps left due to the required alignment of input sections) will be 3740filled with the value, repeated as necessary. If the fill expression 3741is a simple hex number, ie. a string of hex digit starting with `0x' 3742and without a trailing `k' or `M', then an arbitrarily long sequence of 3743hex digits can be used to specify the fill pattern; Leading zeros 3744become part of the pattern too. For all other cases, including extra 3745parentheses or a unary `+', the fill pattern is the four least 3746significant bytes of the value of the expression. In all cases, the 3747number is big-endian. 3748 3749 You can also change the fill value with a `FILL' command in the 3750output section commands; (*note Output Section Data::). 3751 3752 Here is a simple example: 3753 SECTIONS { .text : { *(.text) } =0x90909090 } 3754 3755 3756File: ld.info, Node: Overlay Description, Prev: Output Section Attributes, Up: SECTIONS 3757 37583.6.9 Overlay Description 3759------------------------- 3760 3761An overlay description provides an easy way to describe sections which 3762are to be loaded as part of a single memory image but are to be run at 3763the same memory address. At run time, some sort of overlay manager will 3764copy the overlaid sections in and out of the runtime memory address as 3765required, perhaps by simply manipulating addressing bits. This approach 3766can be useful, for example, when a certain region of memory is faster 3767than another. 3768 3769 Overlays are described using the `OVERLAY' command. The `OVERLAY' 3770command is used within a `SECTIONS' command, like an output section 3771description. The full syntax of the `OVERLAY' command is as follows: 3772 OVERLAY [START] : [NOCROSSREFS] [AT ( LDADDR )] 3773 { 3774 SECNAME1 3775 { 3776 OUTPUT-SECTION-COMMAND 3777 OUTPUT-SECTION-COMMAND 3778 ... 3779 } [:PHDR...] [=FILL] 3780 SECNAME2 3781 { 3782 OUTPUT-SECTION-COMMAND 3783 OUTPUT-SECTION-COMMAND 3784 ... 3785 } [:PHDR...] [=FILL] 3786 ... 3787 } [>REGION] [:PHDR...] [=FILL] 3788 3789 Everything is optional except `OVERLAY' (a keyword), and each 3790section must have a name (SECNAME1 and SECNAME2 above). The section 3791definitions within the `OVERLAY' construct are identical to those 3792within the general `SECTIONS' contruct (*note SECTIONS::), except that 3793no addresses and no memory regions may be defined for sections within 3794an `OVERLAY'. 3795 3796 The sections are all defined with the same starting address. The 3797load addresses of the sections are arranged such that they are 3798consecutive in memory starting at the load address used for the 3799`OVERLAY' as a whole (as with normal section definitions, the load 3800address is optional, and defaults to the start address; the start 3801address is also optional, and defaults to the current value of the 3802location counter). 3803 3804 If the `NOCROSSREFS' keyword is used, and there any references among 3805the sections, the linker will report an error. Since the sections all 3806run at the same address, it normally does not make sense for one 3807section to refer directly to another. *Note NOCROSSREFS: Miscellaneous 3808Commands. 3809 3810 For each section within the `OVERLAY', the linker automatically 3811provides two symbols. The symbol `__load_start_SECNAME' is defined as 3812the starting load address of the section. The symbol 3813`__load_stop_SECNAME' is defined as the final load address of the 3814section. Any characters within SECNAME which are not legal within C 3815identifiers are removed. C (or assembler) code may use these symbols 3816to move the overlaid sections around as necessary. 3817 3818 At the end of the overlay, the value of the location counter is set 3819to the start address of the overlay plus the size of the largest 3820section. 3821 3822 Here is an example. Remember that this would appear inside a 3823`SECTIONS' construct. 3824 OVERLAY 0x1000 : AT (0x4000) 3825 { 3826 .text0 { o1/*.o(.text) } 3827 .text1 { o2/*.o(.text) } 3828 } 3829This will define both `.text0' and `.text1' to start at address 38300x1000. `.text0' will be loaded at address 0x4000, and `.text1' will 3831be loaded immediately after `.text0'. The following symbols will be 3832defined if referenced: `__load_start_text0', `__load_stop_text0', 3833`__load_start_text1', `__load_stop_text1'. 3834 3835 C code to copy overlay `.text1' into the overlay area might look 3836like the following. 3837 3838 extern char __load_start_text1, __load_stop_text1; 3839 memcpy ((char *) 0x1000, &__load_start_text1, 3840 &__load_stop_text1 - &__load_start_text1); 3841 3842 Note that the `OVERLAY' command is just syntactic sugar, since 3843everything it does can be done using the more basic commands. The above 3844example could have been written identically as follows. 3845 3846 .text0 0x1000 : AT (0x4000) { o1/*.o(.text) } 3847 PROVIDE (__load_start_text0 = LOADADDR (.text0)); 3848 PROVIDE (__load_stop_text0 = LOADADDR (.text0) + SIZEOF (.text0)); 3849 .text1 0x1000 : AT (0x4000 + SIZEOF (.text0)) { o2/*.o(.text) } 3850 PROVIDE (__load_start_text1 = LOADADDR (.text1)); 3851 PROVIDE (__load_stop_text1 = LOADADDR (.text1) + SIZEOF (.text1)); 3852 . = 0x1000 + MAX (SIZEOF (.text0), SIZEOF (.text1)); 3853 3854 3855File: ld.info, Node: MEMORY, Next: PHDRS, Prev: SECTIONS, Up: Scripts 3856 38573.7 MEMORY Command 3858================== 3859 3860The linker's default configuration permits allocation of all available 3861memory. You can override this by using the `MEMORY' command. 3862 3863 The `MEMORY' command describes the location and size of blocks of 3864memory in the target. You can use it to describe which memory regions 3865may be used by the linker, and which memory regions it must avoid. You 3866can then assign sections to particular memory regions. The linker will 3867set section addresses based on the memory regions, and will warn about 3868regions that become too full. The linker will not shuffle sections 3869around to fit into the available regions. 3870 3871 A linker script may contain at most one use of the `MEMORY' command. 3872However, you can define as many blocks of memory within it as you 3873wish. The syntax is: 3874 MEMORY 3875 { 3876 NAME [(ATTR)] : ORIGIN = ORIGIN, LENGTH = LEN 3877 ... 3878 } 3879 3880 The NAME is a name used in the linker script to refer to the region. 3881The region name has no meaning outside of the linker script. Region 3882names are stored in a separate name space, and will not conflict with 3883symbol names, file names, or section names. Each memory region must 3884have a distinct name within the `MEMORY' command. However you can add 3885later alias names to existing memory regions with the *Note 3886REGION_ALIAS:: command. 3887 3888 The ATTR string is an optional list of attributes that specify 3889whether to use a particular memory region for an input section which is 3890not explicitly mapped in the linker script. As described in *Note 3891SECTIONS::, if you do not specify an output section for some input 3892section, the linker will create an output section with the same name as 3893the input section. If you define region attributes, the linker will use 3894them to select the memory region for the output section that it creates. 3895 3896 The ATTR string must consist only of the following characters: 3897`R' 3898 Read-only section 3899 3900`W' 3901 Read/write section 3902 3903`X' 3904 Executable section 3905 3906`A' 3907 Allocatable section 3908 3909`I' 3910 Initialized section 3911 3912`L' 3913 Same as `I' 3914 3915`!' 3916 Invert the sense of any of the attributes that follow 3917 3918 If a unmapped section matches any of the listed attributes other than 3919`!', it will be placed in the memory region. The `!' attribute 3920reverses this test, so that an unmapped section will be placed in the 3921memory region only if it does not match any of the listed attributes. 3922 3923 The ORIGIN is an numerical expression for the start address of the 3924memory region. The expression must evaluate to a constant and it 3925cannot involve any symbols. The keyword `ORIGIN' may be abbreviated to 3926`org' or `o' (but not, for example, `ORG'). 3927 3928 The LEN is an expression for the size in bytes of the memory region. 3929As with the ORIGIN expression, the expression must be numerical only 3930and must evaluate to a constant. The keyword `LENGTH' may be 3931abbreviated to `len' or `l'. 3932 3933 In the following example, we specify that there are two memory 3934regions available for allocation: one starting at `0' for 256 kilobytes, 3935and the other starting at `0x40000000' for four megabytes. The linker 3936will place into the `rom' memory region every section which is not 3937explicitly mapped into a memory region, and is either read-only or 3938executable. The linker will place other sections which are not 3939explicitly mapped into a memory region into the `ram' memory region. 3940 3941 MEMORY 3942 { 3943 rom (rx) : ORIGIN = 0, LENGTH = 256K 3944 ram (!rx) : org = 0x40000000, l = 4M 3945 } 3946 3947 Once you define a memory region, you can direct the linker to place 3948specific output sections into that memory region by using the `>REGION' 3949output section attribute. For example, if you have a memory region 3950named `mem', you would use `>mem' in the output section definition. 3951*Note Output Section Region::. If no address was specified for the 3952output section, the linker will set the address to the next available 3953address within the memory region. If the combined output sections 3954directed to a memory region are too large for the region, the linker 3955will issue an error message. 3956 3957 It is possible to access the origin and length of a memory in an 3958expression via the `ORIGIN(MEMORY)' and `LENGTH(MEMORY)' functions: 3959 3960 _fstack = ORIGIN(ram) + LENGTH(ram) - 4; 3961 3962 3963File: ld.info, Node: PHDRS, Next: VERSION, Prev: MEMORY, Up: Scripts 3964 39653.8 PHDRS Command 3966================= 3967 3968The ELF object file format uses "program headers", also knows as 3969"segments". The program headers describe how the program should be 3970loaded into memory. You can print them out by using the `objdump' 3971program with the `-p' option. 3972 3973 When you run an ELF program on a native ELF system, the system loader 3974reads the program headers in order to figure out how to load the 3975program. This will only work if the program headers are set correctly. 3976This manual does not describe the details of how the system loader 3977interprets program headers; for more information, see the ELF ABI. 3978 3979 The linker will create reasonable program headers by default. 3980However, in some cases, you may need to specify the program headers more 3981precisely. You may use the `PHDRS' command for this purpose. When the 3982linker sees the `PHDRS' command in the linker script, it will not 3983create any program headers other than the ones specified. 3984 3985 The linker only pays attention to the `PHDRS' command when 3986generating an ELF output file. In other cases, the linker will simply 3987ignore `PHDRS'. 3988 3989 This is the syntax of the `PHDRS' command. The words `PHDRS', 3990`FILEHDR', `AT', and `FLAGS' are keywords. 3991 3992 PHDRS 3993 { 3994 NAME TYPE [ FILEHDR ] [ PHDRS ] [ AT ( ADDRESS ) ] 3995 [ FLAGS ( FLAGS ) ] ; 3996 } 3997 3998 The NAME is used only for reference in the `SECTIONS' command of the 3999linker script. It is not put into the output file. Program header 4000names are stored in a separate name space, and will not conflict with 4001symbol names, file names, or section names. Each program header must 4002have a distinct name. The headers are processed in order and it is 4003usual for them to map to sections in ascending load address order. 4004 4005 Certain program header types describe segments of memory which the 4006system loader will load from the file. In the linker script, you 4007specify the contents of these segments by placing allocatable output 4008sections in the segments. You use the `:PHDR' output section attribute 4009to place a section in a particular segment. *Note Output Section 4010Phdr::. 4011 4012 It is normal to put certain sections in more than one segment. This 4013merely implies that one segment of memory contains another. You may 4014repeat `:PHDR', using it once for each segment which should contain the 4015section. 4016 4017 If you place a section in one or more segments using `:PHDR', then 4018the linker will place all subsequent allocatable sections which do not 4019specify `:PHDR' in the same segments. This is for convenience, since 4020generally a whole set of contiguous sections will be placed in a single 4021segment. You can use `:NONE' to override the default segment and tell 4022the linker to not put the section in any segment at all. 4023 4024 You may use the `FILEHDR' and `PHDRS' keywords after the program 4025header type to further describe the contents of the segment. The 4026`FILEHDR' keyword means that the segment should include the ELF file 4027header. The `PHDRS' keyword means that the segment should include the 4028ELF program headers themselves. If applied to a loadable segment 4029(`PT_LOAD'), all prior loadable segments must have one of these 4030keywords. 4031 4032 The TYPE may be one of the following. The numbers indicate the 4033value of the keyword. 4034 4035`PT_NULL' (0) 4036 Indicates an unused program header. 4037 4038`PT_LOAD' (1) 4039 Indicates that this program header describes a segment to be 4040 loaded from the file. 4041 4042`PT_DYNAMIC' (2) 4043 Indicates a segment where dynamic linking information can be found. 4044 4045`PT_INTERP' (3) 4046 Indicates a segment where the name of the program interpreter may 4047 be found. 4048 4049`PT_NOTE' (4) 4050 Indicates a segment holding note information. 4051 4052`PT_SHLIB' (5) 4053 A reserved program header type, defined but not specified by the 4054 ELF ABI. 4055 4056`PT_PHDR' (6) 4057 Indicates a segment where the program headers may be found. 4058 4059EXPRESSION 4060 An expression giving the numeric type of the program header. This 4061 may be used for types not defined above. 4062 4063 You can specify that a segment should be loaded at a particular 4064address in memory by using an `AT' expression. This is identical to the 4065`AT' command used as an output section attribute (*note Output Section 4066LMA::). The `AT' command for a program header overrides the output 4067section attribute. 4068 4069 The linker will normally set the segment flags based on the sections 4070which comprise the segment. You may use the `FLAGS' keyword to 4071explicitly specify the segment flags. The value of FLAGS must be an 4072integer. It is used to set the `p_flags' field of the program header. 4073 4074 Here is an example of `PHDRS'. This shows a typical set of program 4075headers used on a native ELF system. 4076 4077 PHDRS 4078 { 4079 headers PT_PHDR PHDRS ; 4080 interp PT_INTERP ; 4081 text PT_LOAD FILEHDR PHDRS ; 4082 data PT_LOAD ; 4083 dynamic PT_DYNAMIC ; 4084 } 4085 4086 SECTIONS 4087 { 4088 . = SIZEOF_HEADERS; 4089 .interp : { *(.interp) } :text :interp 4090 .text : { *(.text) } :text 4091 .rodata : { *(.rodata) } /* defaults to :text */ 4092 ... 4093 . = . + 0x1000; /* move to a new page in memory */ 4094 .data : { *(.data) } :data 4095 .dynamic : { *(.dynamic) } :data :dynamic 4096 ... 4097 } 4098 4099 4100File: ld.info, Node: VERSION, Next: Expressions, Prev: PHDRS, Up: Scripts 4101 41023.9 VERSION Command 4103=================== 4104 4105The linker supports symbol versions when using ELF. Symbol versions are 4106only useful when using shared libraries. The dynamic linker can use 4107symbol versions to select a specific version of a function when it runs 4108a program that may have been linked against an earlier version of the 4109shared library. 4110 4111 You can include a version script directly in the main linker script, 4112or you can supply the version script as an implicit linker script. You 4113can also use the `--version-script' linker option. 4114 4115 The syntax of the `VERSION' command is simply 4116 VERSION { version-script-commands } 4117 4118 The format of the version script commands is identical to that used 4119by Sun's linker in Solaris 2.5. The version script defines a tree of 4120version nodes. You specify the node names and interdependencies in the 4121version script. You can specify which symbols are bound to which 4122version nodes, and you can reduce a specified set of symbols to local 4123scope so that they are not globally visible outside of the shared 4124library. 4125 4126 The easiest way to demonstrate the version script language is with a 4127few examples. 4128 4129 VERS_1.1 { 4130 global: 4131 foo1; 4132 local: 4133 old*; 4134 original*; 4135 new*; 4136 }; 4137 4138 VERS_1.2 { 4139 foo2; 4140 } VERS_1.1; 4141 4142 VERS_2.0 { 4143 bar1; bar2; 4144 extern "C++" { 4145 ns::*; 4146 "f(int, double)"; 4147 }; 4148 } VERS_1.2; 4149 4150 This example version script defines three version nodes. The first 4151version node defined is `VERS_1.1'; it has no other dependencies. The 4152script binds the symbol `foo1' to `VERS_1.1'. It reduces a number of 4153symbols to local scope so that they are not visible outside of the 4154shared library; this is done using wildcard patterns, so that any 4155symbol whose name begins with `old', `original', or `new' is matched. 4156The wildcard patterns available are the same as those used in the shell 4157when matching filenames (also known as "globbing"). However, if you 4158specify the symbol name inside double quotes, then the name is treated 4159as literal, rather than as a glob pattern. 4160 4161 Next, the version script defines node `VERS_1.2'. This node depends 4162upon `VERS_1.1'. The script binds the symbol `foo2' to the version 4163node `VERS_1.2'. 4164 4165 Finally, the version script defines node `VERS_2.0'. This node 4166depends upon `VERS_1.2'. The scripts binds the symbols `bar1' and 4167`bar2' are bound to the version node `VERS_2.0'. 4168 4169 When the linker finds a symbol defined in a library which is not 4170specifically bound to a version node, it will effectively bind it to an 4171unspecified base version of the library. You can bind all otherwise 4172unspecified symbols to a given version node by using `global: *;' 4173somewhere in the version script. Note that it's slightly crazy to use 4174wildcards in a global spec except on the last version node. Global 4175wildcards elsewhere run the risk of accidentally adding symbols to the 4176set exported for an old version. That's wrong since older versions 4177ought to have a fixed set of symbols. 4178 4179 The names of the version nodes have no specific meaning other than 4180what they might suggest to the person reading them. The `2.0' version 4181could just as well have appeared in between `1.1' and `1.2'. However, 4182this would be a confusing way to write a version script. 4183 4184 Node name can be omitted, provided it is the only version node in 4185the version script. Such version script doesn't assign any versions to 4186symbols, only selects which symbols will be globally visible out and 4187which won't. 4188 4189 { global: foo; bar; local: *; }; 4190 4191 When you link an application against a shared library that has 4192versioned symbols, the application itself knows which version of each 4193symbol it requires, and it also knows which version nodes it needs from 4194each shared library it is linked against. Thus at runtime, the dynamic 4195loader can make a quick check to make sure that the libraries you have 4196linked against do in fact supply all of the version nodes that the 4197application will need to resolve all of the dynamic symbols. In this 4198way it is possible for the dynamic linker to know with certainty that 4199all external symbols that it needs will be resolvable without having to 4200search for each symbol reference. 4201 4202 The symbol versioning is in effect a much more sophisticated way of 4203doing minor version checking that SunOS does. The fundamental problem 4204that is being addressed here is that typically references to external 4205functions are bound on an as-needed basis, and are not all bound when 4206the application starts up. If a shared library is out of date, a 4207required interface may be missing; when the application tries to use 4208that interface, it may suddenly and unexpectedly fail. With symbol 4209versioning, the user will get a warning when they start their program if 4210the libraries being used with the application are too old. 4211 4212 There are several GNU extensions to Sun's versioning approach. The 4213first of these is the ability to bind a symbol to a version node in the 4214source file where the symbol is defined instead of in the versioning 4215script. This was done mainly to reduce the burden on the library 4216maintainer. You can do this by putting something like: 4217 __asm__(".symver original_foo,foo@VERS_1.1"); 4218 in the C source file. This renames the function `original_foo' to 4219be an alias for `foo' bound to the version node `VERS_1.1'. The 4220`local:' directive can be used to prevent the symbol `original_foo' 4221from being exported. A `.symver' directive takes precedence over a 4222version script. 4223 4224 The second GNU extension is to allow multiple versions of the same 4225function to appear in a given shared library. In this way you can make 4226an incompatible change to an interface without increasing the major 4227version number of the shared library, while still allowing applications 4228linked against the old interface to continue to function. 4229 4230 To do this, you must use multiple `.symver' directives in the source 4231file. Here is an example: 4232 4233 __asm__(".symver original_foo,foo@"); 4234 __asm__(".symver old_foo,foo@VERS_1.1"); 4235 __asm__(".symver old_foo1,foo@VERS_1.2"); 4236 __asm__(".symver new_foo,foo@@VERS_2.0"); 4237 4238 In this example, `foo@' represents the symbol `foo' bound to the 4239unspecified base version of the symbol. The source file that contains 4240this example would define 4 C functions: `original_foo', `old_foo', 4241`old_foo1', and `new_foo'. 4242 4243 When you have multiple definitions of a given symbol, there needs to 4244be some way to specify a default version to which external references to 4245this symbol will be bound. You can do this with the `foo@@VERS_2.0' 4246type of `.symver' directive. You can only declare one version of a 4247symbol as the default in this manner; otherwise you would effectively 4248have multiple definitions of the same symbol. 4249 4250 If you wish to bind a reference to a specific version of the symbol 4251within the shared library, you can use the aliases of convenience 4252(i.e., `old_foo'), or you can use the `.symver' directive to 4253specifically bind to an external version of the function in question. 4254 4255 You can also specify the language in the version script: 4256 4257 VERSION extern "lang" { version-script-commands } 4258 4259 The supported `lang's are `C', `C++', and `Java'. The linker will 4260iterate over the list of symbols at the link time and demangle them 4261according to `lang' before matching them to the patterns specified in 4262`version-script-commands'. The default `lang' is `C'. 4263 4264 Demangled names may contains spaces and other special characters. As 4265described above, you can use a glob pattern to match demangled names, 4266or you can use a double-quoted string to match the string exactly. In 4267the latter case, be aware that minor differences (such as differing 4268whitespace) between the version script and the demangler output will 4269cause a mismatch. As the exact string generated by the demangler might 4270change in the future, even if the mangled name does not, you should 4271check that all of your version directives are behaving as you expect 4272when you upgrade. 4273 4274 4275File: ld.info, Node: Expressions, Next: Implicit Linker Scripts, Prev: VERSION, Up: Scripts 4276 42773.10 Expressions in Linker Scripts 4278================================== 4279 4280The syntax for expressions in the linker script language is identical to 4281that of C expressions. All expressions are evaluated as integers. All 4282expressions are evaluated in the same size, which is 32 bits if both the 4283host and target are 32 bits, and is otherwise 64 bits. 4284 4285 You can use and set symbol values in expressions. 4286 4287 The linker defines several special purpose builtin functions for use 4288in expressions. 4289 4290* Menu: 4291 4292* Constants:: Constants 4293* Symbolic Constants:: Symbolic constants 4294* Symbols:: Symbol Names 4295* Orphan Sections:: Orphan Sections 4296* Location Counter:: The Location Counter 4297* Operators:: Operators 4298* Evaluation:: Evaluation 4299* Expression Section:: The Section of an Expression 4300* Builtin Functions:: Builtin Functions 4301 4302 4303File: ld.info, Node: Constants, Next: Symbolic Constants, Up: Expressions 4304 43053.10.1 Constants 4306---------------- 4307 4308All constants are integers. 4309 4310 As in C, the linker considers an integer beginning with `0' to be 4311octal, and an integer beginning with `0x' or `0X' to be hexadecimal. 4312Alternatively the linker accepts suffixes of `h' or `H' for 4313hexadeciaml, `o' or `O' for octal, `b' or `B' for binary and `d' or `D' 4314for decimal. Any integer value without a prefix or a suffix is 4315considered to be decimal. 4316 4317 In addition, you can use the suffixes `K' and `M' to scale a 4318constant by `1024' or `1024*1024' respectively. For example, the 4319following all refer to the same quantity: 4320 4321 _fourk_1 = 4K; 4322 _fourk_2 = 4096; 4323 _fourk_3 = 0x1000; 4324 _fourk_4 = 10000o; 4325 4326 Note - the `K' and `M' suffixes cannot be used in conjunction with 4327the base suffixes mentioned above. 4328 4329 4330File: ld.info, Node: Symbolic Constants, Next: Symbols, Prev: Constants, Up: Expressions 4331 43323.10.2 Symbolic Constants 4333------------------------- 4334 4335It is possible to refer to target specific constants via the use of the 4336`CONSTANT(NAME)' operator, where NAME is one of: 4337 4338`MAXPAGESIZE' 4339 The target's maximum page size. 4340 4341`COMMONPAGESIZE' 4342 The target's default page size. 4343 4344 So for example: 4345 4346 .text ALIGN (CONSTANT (MAXPAGESIZE)) : { *(.text) } 4347 4348 will create a text section aligned to the largest page boundary 4349supported by the target. 4350 4351 4352File: ld.info, Node: Symbols, Next: Orphan Sections, Prev: Symbolic Constants, Up: Expressions 4353 43543.10.3 Symbol Names 4355------------------- 4356 4357Unless quoted, symbol names start with a letter, underscore, or period 4358and may include letters, digits, underscores, periods, and hyphens. 4359Unquoted symbol names must not conflict with any keywords. You can 4360specify a symbol which contains odd characters or has the same name as a 4361keyword by surrounding the symbol name in double quotes: 4362 "SECTION" = 9; 4363 "with a space" = "also with a space" + 10; 4364 4365 Since symbols can contain many non-alphabetic characters, it is 4366safest to delimit symbols with spaces. For example, `A-B' is one 4367symbol, whereas `A - B' is an expression involving subtraction. 4368 4369 4370File: ld.info, Node: Orphan Sections, Next: Location Counter, Prev: Symbols, Up: Expressions 4371 43723.10.4 Orphan Sections 4373---------------------- 4374 4375Orphan sections are sections present in the input files which are not 4376explicitly placed into the output file by the linker script. The 4377linker will still copy these sections into the output file, but it has 4378to guess as to where they should be placed. The linker uses a simple 4379heuristic to do this. It attempts to place orphan sections after 4380non-orphan sections of the same attribute, such as code vs data, 4381loadable vs non-loadable, etc. If there is not enough room to do this 4382then it places at the end of the file. 4383 4384 For ELF targets, the attribute of the section includes section type 4385as well as section flag. 4386 4387 If an orphaned section's name is representable as a C identifier then 4388the linker will automatically *note PROVIDE:: two symbols: 4389__start_SECNAME and __end_SECNAME, where SECNAME is the name of the 4390section. These indicate the start address and end address of the 4391orphaned section respectively. Note: most section names are not 4392representable as C identifiers because they contain a `.' character. 4393 4394 4395File: ld.info, Node: Location Counter, Next: Operators, Prev: Orphan Sections, Up: Expressions 4396 43973.10.5 The Location Counter 4398--------------------------- 4399 4400The special linker variable "dot" `.' always contains the current 4401output location counter. Since the `.' always refers to a location in 4402an output section, it may only appear in an expression within a 4403`SECTIONS' command. The `.' symbol may appear anywhere that an 4404ordinary symbol is allowed in an expression. 4405 4406 Assigning a value to `.' will cause the location counter to be 4407moved. This may be used to create holes in the output section. The 4408location counter may not be moved backwards inside an output section, 4409and may not be moved backwards outside of an output section if so doing 4410creates areas with overlapping LMAs. 4411 4412 SECTIONS 4413 { 4414 output : 4415 { 4416 file1(.text) 4417 . = . + 1000; 4418 file2(.text) 4419 . += 1000; 4420 file3(.text) 4421 } = 0x12345678; 4422 } 4423 In the previous example, the `.text' section from `file1' is located 4424at the beginning of the output section `output'. It is followed by a 44251000 byte gap. Then the `.text' section from `file2' appears, also 4426with a 1000 byte gap following before the `.text' section from `file3'. 4427The notation `= 0x12345678' specifies what data to write in the gaps 4428(*note Output Section Fill::). 4429 4430 Note: `.' actually refers to the byte offset from the start of the 4431current containing object. Normally this is the `SECTIONS' statement, 4432whose start address is 0, hence `.' can be used as an absolute address. 4433If `.' is used inside a section description however, it refers to the 4434byte offset from the start of that section, not an absolute address. 4435Thus in a script like this: 4436 4437 SECTIONS 4438 { 4439 . = 0x100 4440 .text: { 4441 *(.text) 4442 . = 0x200 4443 } 4444 . = 0x500 4445 .data: { 4446 *(.data) 4447 . += 0x600 4448 } 4449 } 4450 4451 The `.text' section will be assigned a starting address of 0x100 and 4452a size of exactly 0x200 bytes, even if there is not enough data in the 4453`.text' input sections to fill this area. (If there is too much data, 4454an error will be produced because this would be an attempt to move `.' 4455backwards). The `.data' section will start at 0x500 and it will have 4456an extra 0x600 bytes worth of space after the end of the values from 4457the `.data' input sections and before the end of the `.data' output 4458section itself. 4459 4460 Setting symbols to the value of the location counter outside of an 4461output section statement can result in unexpected values if the linker 4462needs to place orphan sections. For example, given the following: 4463 4464 SECTIONS 4465 { 4466 start_of_text = . ; 4467 .text: { *(.text) } 4468 end_of_text = . ; 4469 4470 start_of_data = . ; 4471 .data: { *(.data) } 4472 end_of_data = . ; 4473 } 4474 4475 If the linker needs to place some input section, e.g. `.rodata', not 4476mentioned in the script, it might choose to place that section between 4477`.text' and `.data'. You might think the linker should place `.rodata' 4478on the blank line in the above script, but blank lines are of no 4479particular significance to the linker. As well, the linker doesn't 4480associate the above symbol names with their sections. Instead, it 4481assumes that all assignments or other statements belong to the previous 4482output section, except for the special case of an assignment to `.'. 4483I.e., the linker will place the orphan `.rodata' section as if the 4484script was written as follows: 4485 4486 SECTIONS 4487 { 4488 start_of_text = . ; 4489 .text: { *(.text) } 4490 end_of_text = . ; 4491 4492 start_of_data = . ; 4493 .rodata: { *(.rodata) } 4494 .data: { *(.data) } 4495 end_of_data = . ; 4496 } 4497 4498 This may or may not be the script author's intention for the value of 4499`start_of_data'. One way to influence the orphan section placement is 4500to assign the location counter to itself, as the linker assumes that an 4501assignment to `.' is setting the start address of a following output 4502section and thus should be grouped with that section. So you could 4503write: 4504 4505 SECTIONS 4506 { 4507 start_of_text = . ; 4508 .text: { *(.text) } 4509 end_of_text = . ; 4510 4511 . = . ; 4512 start_of_data = . ; 4513 .data: { *(.data) } 4514 end_of_data = . ; 4515 } 4516 4517 Now, the orphan `.rodata' section will be placed between 4518`end_of_text' and `start_of_data'. 4519 4520 4521File: ld.info, Node: Operators, Next: Evaluation, Prev: Location Counter, Up: Expressions 4522 45233.10.6 Operators 4524---------------- 4525 4526The linker recognizes the standard C set of arithmetic operators, with 4527the standard bindings and precedence levels: 4528 precedence associativity Operators Notes 4529 (highest) 4530 1 left ! - ~ (1) 4531 2 left * / % 4532 3 left + - 4533 4 left >> << 4534 5 left == != > < <= >= 4535 6 left & 4536 7 left | 4537 8 left && 4538 9 left || 4539 10 right ? : 4540 11 right &= += -= *= /= (2) 4541 (lowest) 4542 Notes: (1) Prefix operators (2) *Note Assignments::. 4543 4544 4545File: ld.info, Node: Evaluation, Next: Expression Section, Prev: Operators, Up: Expressions 4546 45473.10.7 Evaluation 4548----------------- 4549 4550The linker evaluates expressions lazily. It only computes the value of 4551an expression when absolutely necessary. 4552 4553 The linker needs some information, such as the value of the start 4554address of the first section, and the origins and lengths of memory 4555regions, in order to do any linking at all. These values are computed 4556as soon as possible when the linker reads in the linker script. 4557 4558 However, other values (such as symbol values) are not known or needed 4559until after storage allocation. Such values are evaluated later, when 4560other information (such as the sizes of output sections) is available 4561for use in the symbol assignment expression. 4562 4563 The sizes of sections cannot be known until after allocation, so 4564assignments dependent upon these are not performed until after 4565allocation. 4566 4567 Some expressions, such as those depending upon the location counter 4568`.', must be evaluated during section allocation. 4569 4570 If the result of an expression is required, but the value is not 4571available, then an error results. For example, a script like the 4572following 4573 SECTIONS 4574 { 4575 .text 9+this_isnt_constant : 4576 { *(.text) } 4577 } 4578will cause the error message `non constant expression for initial 4579address'. 4580 4581 4582File: ld.info, Node: Expression Section, Next: Builtin Functions, Prev: Evaluation, Up: Expressions 4583 45843.10.8 The Section of an Expression 4585----------------------------------- 4586 4587Addresses and symbols may be section relative, or absolute. A section 4588relative symbol is relocatable. If you request relocatable output 4589using the `-r' option, a further link operation may change the value of 4590a section relative symbol. On the other hand, an absolute symbol will 4591retain the same value throughout any further link operations. 4592 4593 Some terms in linker expressions are addresses. This is true of 4594section relative symbols and for builtin functions that return an 4595address, such as `ADDR', `LOADADDR', `ORIGIN' and `SEGMENT_START'. 4596Other terms are simply numbers, or are builtin functions that return a 4597non-address value, such as `LENGTH'. One complication is that unless 4598you set `LD_FEATURE ("SANE_EXPR")' (*note Miscellaneous Commands::), 4599numbers and absolute symbols are treated differently depending on their 4600location, for compatibility with older versions of `ld'. Expressions 4601appearing outside an output section definition treat all numbers as 4602absolute addresses. Expressions appearing inside an output section 4603definition treat absolute symbols as numbers. If `LD_FEATURE 4604("SANE_EXPR")' is given, then absolute symbols and numbers are simply 4605treated as numbers everywhere. 4606 4607 In the following simple example, 4608 4609 SECTIONS 4610 { 4611 . = 0x100; 4612 __executable_start = 0x100; 4613 .data : 4614 { 4615 . = 0x10; 4616 __data_start = 0x10; 4617 *(.data) 4618 } 4619 ... 4620 } 4621 4622 both `.' and `__executable_start' are set to the absolute address 46230x100 in the first two assignments, then both `.' and `__data_start' 4624are set to 0x10 relative to the `.data' section in the second two 4625assignments. 4626 4627 For expressions involving numbers, relative addresses and absolute 4628addresses, ld follows these rules to evaluate terms: 4629 4630 * Unary operations on a relative address, and binary operations on 4631 two relative addresses in the same section or between one relative 4632 address and a number, apply the operator to the offset part of the 4633 address(es). 4634 4635 * Unary operations on an absolute address, and binary operations on 4636 one or more absolute addresses or on two relative addresses not in 4637 the same section, first convert any non-absolute term to an 4638 absolute address before applying the operator. 4639 4640 The result section of each sub-expression is as follows: 4641 4642 * An operation involving only numbers results in a number. 4643 4644 * The result of comparisons, `&&' and `||' is also a number. 4645 4646 * The result of other binary arithmetic and logical operations on two 4647 relative addresses in the same section or two absolute addresess 4648 (after above conversions) is also a number. 4649 4650 * The result of other operations on relative addresses or one 4651 relative address and a number, is a relative address in the same 4652 section as the relative operand(s). 4653 4654 * The result of other operations on absolute addresses (after above 4655 conversions) is an absolute address. 4656 4657 You can use the builtin function `ABSOLUTE' to force an expression 4658to be absolute when it would otherwise be relative. For example, to 4659create an absolute symbol set to the address of the end of the output 4660section `.data': 4661 SECTIONS 4662 { 4663 .data : { *(.data) _edata = ABSOLUTE(.); } 4664 } 4665 If `ABSOLUTE' were not used, `_edata' would be relative to the 4666`.data' section. 4667 4668 Using `LOADADDR' also forces an expression absolute, since this 4669particular builtin function returns an absolute address. 4670 4671 4672File: ld.info, Node: Builtin Functions, Prev: Expression Section, Up: Expressions 4673 46743.10.9 Builtin Functions 4675------------------------ 4676 4677The linker script language includes a number of builtin functions for 4678use in linker script expressions. 4679 4680`ABSOLUTE(EXP)' 4681 Return the absolute (non-relocatable, as opposed to non-negative) 4682 value of the expression EXP. Primarily useful to assign an 4683 absolute value to a symbol within a section definition, where 4684 symbol values are normally section relative. *Note Expression 4685 Section::. 4686 4687`ADDR(SECTION)' 4688 Return the address (VMA) of the named SECTION. Your script must 4689 previously have defined the location of that section. In the 4690 following example, `start_of_output_1', `symbol_1' and `symbol_2' 4691 are assigned equivalent values, except that `symbol_1' will be 4692 relative to the `.output1' section while the other two will be 4693 absolute: 4694 SECTIONS { ... 4695 .output1 : 4696 { 4697 start_of_output_1 = ABSOLUTE(.); 4698 ... 4699 } 4700 .output : 4701 { 4702 symbol_1 = ADDR(.output1); 4703 symbol_2 = start_of_output_1; 4704 } 4705 ... } 4706 4707`ALIGN(ALIGN)' 4708`ALIGN(EXP,ALIGN)' 4709 Return the location counter (`.') or arbitrary expression aligned 4710 to the next ALIGN boundary. The single operand `ALIGN' doesn't 4711 change the value of the location counter--it just does arithmetic 4712 on it. The two operand `ALIGN' allows an arbitrary expression to 4713 be aligned upwards (`ALIGN(ALIGN)' is equivalent to `ALIGN(., 4714 ALIGN)'). 4715 4716 Here is an example which aligns the output `.data' section to the 4717 next `0x2000' byte boundary after the preceding section and sets a 4718 variable within the section to the next `0x8000' boundary after the 4719 input sections: 4720 SECTIONS { ... 4721 .data ALIGN(0x2000): { 4722 *(.data) 4723 variable = ALIGN(0x8000); 4724 } 4725 ... } 4726 The first use of `ALIGN' in this example specifies the 4727 location of a section because it is used as the optional ADDRESS 4728 attribute of a section definition (*note Output Section 4729 Address::). The second use of `ALIGN' is used to defines the 4730 value of a symbol. 4731 4732 The builtin function `NEXT' is closely related to `ALIGN'. 4733 4734`ALIGNOF(SECTION)' 4735 Return the alignment in bytes of the named SECTION, if that 4736 section has been allocated. If the section has not been allocated 4737 when this is evaluated, the linker will report an error. In the 4738 following example, the alignment of the `.output' section is 4739 stored as the first value in that section. 4740 SECTIONS{ ... 4741 .output { 4742 LONG (ALIGNOF (.output)) 4743 ... 4744 } 4745 ... } 4746 4747`BLOCK(EXP)' 4748 This is a synonym for `ALIGN', for compatibility with older linker 4749 scripts. It is most often seen when setting the address of an 4750 output section. 4751 4752`DATA_SEGMENT_ALIGN(MAXPAGESIZE, COMMONPAGESIZE)' 4753 This is equivalent to either 4754 (ALIGN(MAXPAGESIZE) + (. & (MAXPAGESIZE - 1))) 4755 or 4756 (ALIGN(MAXPAGESIZE) + (. & (MAXPAGESIZE - COMMONPAGESIZE))) 4757 depending on whether the latter uses fewer COMMONPAGESIZE sized 4758 pages for the data segment (area between the result of this 4759 expression and `DATA_SEGMENT_END') than the former or not. If the 4760 latter form is used, it means COMMONPAGESIZE bytes of runtime 4761 memory will be saved at the expense of up to COMMONPAGESIZE wasted 4762 bytes in the on-disk file. 4763 4764 This expression can only be used directly in `SECTIONS' commands, 4765 not in any output section descriptions and only once in the linker 4766 script. COMMONPAGESIZE should be less or equal to MAXPAGESIZE and 4767 should be the system page size the object wants to be optimized 4768 for (while still working on system page sizes up to MAXPAGESIZE). 4769 4770 Example: 4771 . = DATA_SEGMENT_ALIGN(0x10000, 0x2000); 4772 4773`DATA_SEGMENT_END(EXP)' 4774 This defines the end of data segment for `DATA_SEGMENT_ALIGN' 4775 evaluation purposes. 4776 4777 . = DATA_SEGMENT_END(.); 4778 4779`DATA_SEGMENT_RELRO_END(OFFSET, EXP)' 4780 This defines the end of the `PT_GNU_RELRO' segment when `-z relro' 4781 option is used. Second argument is returned. When `-z relro' 4782 option is not present, `DATA_SEGMENT_RELRO_END' does nothing, 4783 otherwise `DATA_SEGMENT_ALIGN' is padded so that EXP + OFFSET is 4784 aligned to the most commonly used page boundary for particular 4785 target. If present in the linker script, it must always come in 4786 between `DATA_SEGMENT_ALIGN' and `DATA_SEGMENT_END'. 4787 4788 . = DATA_SEGMENT_RELRO_END(24, .); 4789 4790`DEFINED(SYMBOL)' 4791 Return 1 if SYMBOL is in the linker global symbol table and is 4792 defined before the statement using DEFINED in the script, otherwise 4793 return 0. You can use this function to provide default values for 4794 symbols. For example, the following script fragment shows how to 4795 set a global symbol `begin' to the first location in the `.text' 4796 section--but if a symbol called `begin' already existed, its value 4797 is preserved: 4798 4799 SECTIONS { ... 4800 .text : { 4801 begin = DEFINED(begin) ? begin : . ; 4802 ... 4803 } 4804 ... 4805 } 4806 4807`LENGTH(MEMORY)' 4808 Return the length of the memory region named MEMORY. 4809 4810`LOADADDR(SECTION)' 4811 Return the absolute LMA of the named SECTION. (*note Output 4812 Section LMA::). 4813 4814`MAX(EXP1, EXP2)' 4815 Returns the maximum of EXP1 and EXP2. 4816 4817`MIN(EXP1, EXP2)' 4818 Returns the minimum of EXP1 and EXP2. 4819 4820`NEXT(EXP)' 4821 Return the next unallocated address that is a multiple of EXP. 4822 This function is closely related to `ALIGN(EXP)'; unless you use 4823 the `MEMORY' command to define discontinuous memory for the output 4824 file, the two functions are equivalent. 4825 4826`ORIGIN(MEMORY)' 4827 Return the origin of the memory region named MEMORY. 4828 4829`SEGMENT_START(SEGMENT, DEFAULT)' 4830 Return the base address of the named SEGMENT. If an explicit 4831 value has been given for this segment (with a command-line `-T' 4832 option) that value will be returned; otherwise the value will be 4833 DEFAULT. At present, the `-T' command-line option can only be 4834 used to set the base address for the "text", "data", and "bss" 4835 sections, but you can use `SEGMENT_START' with any segment name. 4836 4837`SIZEOF(SECTION)' 4838 Return the size in bytes of the named SECTION, if that section has 4839 been allocated. If the section has not been allocated when this is 4840 evaluated, the linker will report an error. In the following 4841 example, `symbol_1' and `symbol_2' are assigned identical values: 4842 SECTIONS{ ... 4843 .output { 4844 .start = . ; 4845 ... 4846 .end = . ; 4847 } 4848 symbol_1 = .end - .start ; 4849 symbol_2 = SIZEOF(.output); 4850 ... } 4851 4852`SIZEOF_HEADERS' 4853`sizeof_headers' 4854 Return the size in bytes of the output file's headers. This is 4855 information which appears at the start of the output file. You 4856 can use this number when setting the start address of the first 4857 section, if you choose, to facilitate paging. 4858 4859 When producing an ELF output file, if the linker script uses the 4860 `SIZEOF_HEADERS' builtin function, the linker must compute the 4861 number of program headers before it has determined all the section 4862 addresses and sizes. If the linker later discovers that it needs 4863 additional program headers, it will report an error `not enough 4864 room for program headers'. To avoid this error, you must avoid 4865 using the `SIZEOF_HEADERS' function, or you must rework your linker 4866 script to avoid forcing the linker to use additional program 4867 headers, or you must define the program headers yourself using the 4868 `PHDRS' command (*note PHDRS::). 4869 4870 4871File: ld.info, Node: Implicit Linker Scripts, Prev: Expressions, Up: Scripts 4872 48733.11 Implicit Linker Scripts 4874============================ 4875 4876If you specify a linker input file which the linker can not recognize as 4877an object file or an archive file, it will try to read the file as a 4878linker script. If the file can not be parsed as a linker script, the 4879linker will report an error. 4880 4881 An implicit linker script will not replace the default linker script. 4882 4883 Typically an implicit linker script would contain only symbol 4884assignments, or the `INPUT', `GROUP', or `VERSION' commands. 4885 4886 Any input files read because of an implicit linker script will be 4887read at the position in the command line where the implicit linker 4888script was read. This can affect archive searching. 4889 4890 4891File: ld.info, Node: Machine Dependent, Next: BFD, Prev: Scripts, Up: Top 4892 48934 Machine Dependent Features 4894**************************** 4895 4896`ld' has additional features on some platforms; the following sections 4897describe them. Machines where `ld' has no additional functionality are 4898not listed. 4899 4900* Menu: 4901 4902 4903* H8/300:: `ld' and the H8/300 4904 4905* i960:: `ld' and the Intel 960 family 4906 4907* ARM:: `ld' and the ARM family 4908 4909* HPPA ELF32:: `ld' and HPPA 32-bit ELF 4910 4911* M68K:: `ld' and the Motorola 68K family 4912 4913* MMIX:: `ld' and MMIX 4914 4915* MSP430:: `ld' and MSP430 4916 4917* M68HC11/68HC12:: `ld' and the Motorola 68HC11 and 68HC12 families 4918 4919* PowerPC ELF32:: `ld' and PowerPC 32-bit ELF Support 4920 4921* PowerPC64 ELF64:: `ld' and PowerPC64 64-bit ELF Support 4922 4923* SPU ELF:: `ld' and SPU ELF Support 4924 4925* TI COFF:: `ld' and TI COFF 4926 4927* WIN32:: `ld' and WIN32 (cygwin/mingw) 4928 4929* Xtensa:: `ld' and Xtensa Processors 4930 4931 4932File: ld.info, Node: H8/300, Next: i960, Up: Machine Dependent 4933 49344.1 `ld' and the H8/300 4935======================= 4936 4937For the H8/300, `ld' can perform these global optimizations when you 4938specify the `--relax' command-line option. 4939 4940_relaxing address modes_ 4941 `ld' finds all `jsr' and `jmp' instructions whose targets are 4942 within eight bits, and turns them into eight-bit program-counter 4943 relative `bsr' and `bra' instructions, respectively. 4944 4945_synthesizing instructions_ 4946 `ld' finds all `mov.b' instructions which use the sixteen-bit 4947 absolute address form, but refer to the top page of memory, and 4948 changes them to use the eight-bit address form. (That is: the 4949 linker turns `mov.b `@'AA:16' into `mov.b `@'AA:8' whenever the 4950 address AA is in the top page of memory). 4951 4952_bit manipulation instructions_ 4953 `ld' finds all bit manipulation instructions like `band, bclr, 4954 biand, bild, bior, bist, bixor, bld, bnot, bor, bset, bst, btst, 4955 bxor' which use 32 bit and 16 bit absolute address form, but refer 4956 to the top page of memory, and changes them to use the 8 bit 4957 address form. (That is: the linker turns `bset #xx:3,`@'AA:32' 4958 into `bset #xx:3,`@'AA:8' whenever the address AA is in the top 4959 page of memory). 4960 4961_system control instructions_ 4962 `ld' finds all `ldc.w, stc.w' instructions which use the 32 bit 4963 absolute address form, but refer to the top page of memory, and 4964 changes them to use 16 bit address form. (That is: the linker 4965 turns `ldc.w `@'AA:32,ccr' into `ldc.w `@'AA:16,ccr' whenever the 4966 address AA is in the top page of memory). 4967 4968 4969File: ld.info, Node: i960, Next: ARM, Prev: H8/300, Up: Machine Dependent 4970 49714.2 `ld' and the Intel 960 Family 4972================================= 4973 4974You can use the `-AARCHITECTURE' command line option to specify one of 4975the two-letter names identifying members of the 960 family; the option 4976specifies the desired output target, and warns of any incompatible 4977instructions in the input files. It also modifies the linker's search 4978strategy for archive libraries, to support the use of libraries 4979specific to each particular architecture, by including in the search 4980loop names suffixed with the string identifying the architecture. 4981 4982 For example, if your `ld' command line included `-ACA' as well as 4983`-ltry', the linker would look (in its built-in search paths, and in 4984any paths you specify with `-L') for a library with the names 4985 4986 try 4987 libtry.a 4988 tryca 4989 libtryca.a 4990 4991The first two possibilities would be considered in any event; the last 4992two are due to the use of `-ACA'. 4993 4994 You can meaningfully use `-A' more than once on a command line, since 4995the 960 architecture family allows combination of target architectures; 4996each use will add another pair of name variants to search for when `-l' 4997specifies a library. 4998 4999 `ld' supports the `--relax' option for the i960 family. If you 5000specify `--relax', `ld' finds all `balx' and `calx' instructions whose 5001targets are within 24 bits, and turns them into 24-bit program-counter 5002relative `bal' and `cal' instructions, respectively. `ld' also turns 5003`cal' instructions into `bal' instructions when it determines that the 5004target subroutine is a leaf routine (that is, the target subroutine does 5005not itself call any subroutines). 5006 5007 The `--fix-cortex-a8' switch enables a link-time workaround for an 5008erratum in certain Cortex-A8 processors. The workaround is enabled by 5009default if you are targeting the ARM v7-A architecture profile. It can 5010be enabled otherwise by specifying `--fix-cortex-a8', or disabled 5011unconditionally by specifying `--no-fix-cortex-a8'. 5012 5013 The erratum only affects Thumb-2 code. Please contact ARM for 5014further details. 5015 5016 The `--no-merge-exidx-entries' switch disables the merging of 5017adjacent exidx entries in debuginfo. 5018 5019 5020File: ld.info, Node: M68HC11/68HC12, Next: PowerPC ELF32, Prev: MSP430, Up: Machine Dependent 5021 50224.3 `ld' and the Motorola 68HC11 and 68HC12 families 5023==================================================== 5024 50254.3.1 Linker Relaxation 5026----------------------- 5027 5028For the Motorola 68HC11, `ld' can perform these global optimizations 5029when you specify the `--relax' command-line option. 5030 5031_relaxing address modes_ 5032 `ld' finds all `jsr' and `jmp' instructions whose targets are 5033 within eight bits, and turns them into eight-bit program-counter 5034 relative `bsr' and `bra' instructions, respectively. 5035 5036 `ld' also looks at all 16-bit extended addressing modes and 5037 transforms them in a direct addressing mode when the address is in 5038 page 0 (between 0 and 0x0ff). 5039 5040_relaxing gcc instruction group_ 5041 When `gcc' is called with `-mrelax', it can emit group of 5042 instructions that the linker can optimize to use a 68HC11 direct 5043 addressing mode. These instructions consists of `bclr' or `bset' 5044 instructions. 5045 5046 50474.3.2 Trampoline Generation 5048--------------------------- 5049 5050For 68HC11 and 68HC12, `ld' can generate trampoline code to call a far 5051function using a normal `jsr' instruction. The linker will also change 5052the relocation to some far function to use the trampoline address 5053instead of the function address. This is typically the case when a 5054pointer to a function is taken. The pointer will in fact point to the 5055function trampoline. 5056 5057 5058File: ld.info, Node: ARM, Next: HPPA ELF32, Prev: i960, Up: Machine Dependent 5059 50604.4 `ld' and the ARM family 5061=========================== 5062 5063For the ARM, `ld' will generate code stubs to allow functions calls 5064between ARM and Thumb code. These stubs only work with code that has 5065been compiled and assembled with the `-mthumb-interwork' command line 5066option. If it is necessary to link with old ARM object files or 5067libraries, which have not been compiled with the -mthumb-interwork 5068option then the `--support-old-code' command line switch should be 5069given to the linker. This will make it generate larger stub functions 5070which will work with non-interworking aware ARM code. Note, however, 5071the linker does not support generating stubs for function calls to 5072non-interworking aware Thumb code. 5073 5074 The `--thumb-entry' switch is a duplicate of the generic `--entry' 5075switch, in that it sets the program's starting address. But it also 5076sets the bottom bit of the address, so that it can be branched to using 5077a BX instruction, and the program will start executing in Thumb mode 5078straight away. 5079 5080 The `--use-nul-prefixed-import-tables' switch is specifying, that 5081the import tables idata4 and idata5 have to be generated with a zero 5082elememt prefix for import libraries. This is the old style to generate 5083import tables. By default this option is turned off. 5084 5085 The `--be8' switch instructs `ld' to generate BE8 format 5086executables. This option is only valid when linking big-endian objects. 5087The resulting image will contain big-endian data and little-endian code. 5088 5089 The `R_ARM_TARGET1' relocation is typically used for entries in the 5090`.init_array' section. It is interpreted as either `R_ARM_REL32' or 5091`R_ARM_ABS32', depending on the target. The `--target1-rel' and 5092`--target1-abs' switches override the default. 5093 5094 The `--target2=type' switch overrides the default definition of the 5095`R_ARM_TARGET2' relocation. Valid values for `type', their meanings, 5096and target defaults are as follows: 5097`rel' 5098 `R_ARM_REL32' (arm*-*-elf, arm*-*-eabi) 5099 5100`abs' 5101 `R_ARM_ABS32' (arm*-*-symbianelf) 5102 5103`got-rel' 5104 `R_ARM_GOT_PREL' (arm*-*-linux, arm*-*-*bsd) 5105 5106 The `R_ARM_V4BX' relocation (defined by the ARM AAELF specification) 5107enables objects compiled for the ARMv4 architecture to be 5108interworking-safe when linked with other objects compiled for ARMv4t, 5109but also allows pure ARMv4 binaries to be built from the same ARMv4 5110objects. 5111 5112 In the latter case, the switch `--fix-v4bx' must be passed to the 5113linker, which causes v4t `BX rM' instructions to be rewritten as `MOV 5114PC,rM', since v4 processors do not have a `BX' instruction. 5115 5116 In the former case, the switch should not be used, and `R_ARM_V4BX' 5117relocations are ignored. 5118 5119 Replace `BX rM' instructions identified by `R_ARM_V4BX' relocations 5120with a branch to the following veneer: 5121 5122 TST rM, #1 5123 MOVEQ PC, rM 5124 BX Rn 5125 5126 This allows generation of libraries/applications that work on ARMv4 5127cores and are still interworking safe. Note that the above veneer 5128clobbers the condition flags, so may cause incorrect progrm behavior in 5129rare cases. 5130 5131 The `--use-blx' switch enables the linker to use ARM/Thumb BLX 5132instructions (available on ARMv5t and above) in various situations. 5133Currently it is used to perform calls via the PLT from Thumb code using 5134BLX rather than using BX and a mode-switching stub before each PLT 5135entry. This should lead to such calls executing slightly faster. 5136 5137 This option is enabled implicitly for SymbianOS, so there is no need 5138to specify it if you are using that target. 5139 5140 The `--vfp11-denorm-fix' switch enables a link-time workaround for a 5141bug in certain VFP11 coprocessor hardware, which sometimes allows 5142instructions with denorm operands (which must be handled by support 5143code) to have those operands overwritten by subsequent instructions 5144before the support code can read the intended values. 5145 5146 The bug may be avoided in scalar mode if you allow at least one 5147intervening instruction between a VFP11 instruction which uses a 5148register and another instruction which writes to the same register, or 5149at least two intervening instructions if vector mode is in use. The bug 5150only affects full-compliance floating-point mode: you do not need this 5151workaround if you are using "runfast" mode. Please contact ARM for 5152further details. 5153 5154 If you know you are using buggy VFP11 hardware, you can enable this 5155workaround by specifying the linker option `--vfp-denorm-fix=scalar' if 5156you are using the VFP11 scalar mode only, or `--vfp-denorm-fix=vector' 5157if you are using vector mode (the latter also works for scalar code). 5158The default is `--vfp-denorm-fix=none'. 5159 5160 If the workaround is enabled, instructions are scanned for 5161potentially-troublesome sequences, and a veneer is created for each 5162such sequence which may trigger the erratum. The veneer consists of the 5163first instruction of the sequence and a branch back to the subsequent 5164instruction. The original instruction is then replaced with a branch to 5165the veneer. The extra cycles required to call and return from the veneer 5166are sufficient to avoid the erratum in both the scalar and vector cases. 5167 5168 The `--no-enum-size-warning' switch prevents the linker from warning 5169when linking object files that specify incompatible EABI enumeration 5170size attributes. For example, with this switch enabled, linking of an 5171object file using 32-bit enumeration values with another using 5172enumeration values fitted into the smallest possible space will not be 5173diagnosed. 5174 5175 The `--no-wchar-size-warning' switch prevents the linker from 5176warning when linking object files that specify incompatible EABI 5177`wchar_t' size attributes. For example, with this switch enabled, 5178linking of an object file using 32-bit `wchar_t' values with another 5179using 16-bit `wchar_t' values will not be diagnosed. 5180 5181 The `--pic-veneer' switch makes the linker use PIC sequences for 5182ARM/Thumb interworking veneers, even if the rest of the binary is not 5183PIC. This avoids problems on uClinux targets where `--emit-relocs' is 5184used to generate relocatable binaries. 5185 5186 The linker will automatically generate and insert small sequences of 5187code into a linked ARM ELF executable whenever an attempt is made to 5188perform a function call to a symbol that is too far away. The 5189placement of these sequences of instructions - called stubs - is 5190controlled by the command line option `--stub-group-size=N'. The 5191placement is important because a poor choice can create a need for 5192duplicate stubs, increasing the code sizw. The linker will try to 5193group stubs together in order to reduce interruptions to the flow of 5194code, but it needs guidance as to how big these groups should be and 5195where they should be placed. 5196 5197 The value of `N', the parameter to the `--stub-group-size=' option 5198controls where the stub groups are placed. If it is negative then all 5199stubs are placed after the first branch that needs them. If it is 5200positive then the stubs can be placed either before or after the 5201branches that need them. If the value of `N' is 1 (either +1 or -1) 5202then the linker will choose exactly where to place groups of stubs, 5203using its built in heuristics. A value of `N' greater than 1 (or 5204smaller than -1) tells the linker that a single group of stubs can 5205service at most `N' bytes from the input sections. 5206 5207 The default, if `--stub-group-size=' is not specified, is `N = +1'. 5208 5209 Farcalls stubs insertion is fully supported for the ARM-EABI target 5210only, because it relies on object files properties not present 5211otherwise. 5212 5213 5214File: ld.info, Node: HPPA ELF32, Next: M68K, Prev: ARM, Up: Machine Dependent 5215 52164.5 `ld' and HPPA 32-bit ELF Support 5217==================================== 5218 5219When generating a shared library, `ld' will by default generate import 5220stubs suitable for use with a single sub-space application. The 5221`--multi-subspace' switch causes `ld' to generate export stubs, and 5222different (larger) import stubs suitable for use with multiple 5223sub-spaces. 5224 5225 Long branch stubs and import/export stubs are placed by `ld' in stub 5226sections located between groups of input sections. `--stub-group-size' 5227specifies the maximum size of a group of input sections handled by one 5228stub section. Since branch offsets are signed, a stub section may 5229serve two groups of input sections, one group before the stub section, 5230and one group after it. However, when using conditional branches that 5231require stubs, it may be better (for branch prediction) that stub 5232sections only serve one group of input sections. A negative value for 5233`N' chooses this scheme, ensuring that branches to stubs always use a 5234negative offset. Two special values of `N' are recognized, `1' and 5235`-1'. These both instruct `ld' to automatically size input section 5236groups for the branch types detected, with the same behaviour regarding 5237stub placement as other positive or negative values of `N' respectively. 5238 5239 Note that `--stub-group-size' does not split input sections. A 5240single input section larger than the group size specified will of course 5241create a larger group (of one section). If input sections are too 5242large, it may not be possible for a branch to reach its stub. 5243 5244 5245File: ld.info, Node: M68K, Next: MMIX, Prev: HPPA ELF32, Up: Machine Dependent 5246 52474.6 `ld' and the Motorola 68K family 5248==================================== 5249 5250The `--got=TYPE' option lets you choose the GOT generation scheme. The 5251choices are `single', `negative', `multigot' and `target'. When 5252`target' is selected the linker chooses the default GOT generation 5253scheme for the current target. `single' tells the linker to generate a 5254single GOT with entries only at non-negative offsets. `negative' 5255instructs the linker to generate a single GOT with entries at both 5256negative and positive offsets. Not all environments support such GOTs. 5257`multigot' allows the linker to generate several GOTs in the output 5258file. All GOT references from a single input object file access the 5259same GOT, but references from different input object files might access 5260different GOTs. Not all environments support such GOTs. 5261 5262 5263File: ld.info, Node: MMIX, Next: MSP430, Prev: M68K, Up: Machine Dependent 5264 52654.7 `ld' and MMIX 5266================= 5267 5268For MMIX, there is a choice of generating `ELF' object files or `mmo' 5269object files when linking. The simulator `mmix' understands the `mmo' 5270format. The binutils `objcopy' utility can translate between the two 5271formats. 5272 5273 There is one special section, the `.MMIX.reg_contents' section. 5274Contents in this section is assumed to correspond to that of global 5275registers, and symbols referring to it are translated to special 5276symbols, equal to registers. In a final link, the start address of the 5277`.MMIX.reg_contents' section corresponds to the first allocated global 5278register multiplied by 8. Register `$255' is not included in this 5279section; it is always set to the program entry, which is at the symbol 5280`Main' for `mmo' files. 5281 5282 Global symbols with the prefix `__.MMIX.start.', for example 5283`__.MMIX.start..text' and `__.MMIX.start..data' are special. The 5284default linker script uses these to set the default start address of a 5285section. 5286 5287 Initial and trailing multiples of zero-valued 32-bit words in a 5288section, are left out from an mmo file. 5289 5290 5291File: ld.info, Node: MSP430, Next: M68HC11/68HC12, Prev: MMIX, Up: Machine Dependent 5292 52934.8 `ld' and MSP430 5294=================== 5295 5296For the MSP430 it is possible to select the MPU architecture. The flag 5297`-m [mpu type]' will select an appropriate linker script for selected 5298MPU type. (To get a list of known MPUs just pass `-m help' option to 5299the linker). 5300 5301 The linker will recognize some extra sections which are MSP430 5302specific: 5303 5304``.vectors'' 5305 Defines a portion of ROM where interrupt vectors located. 5306 5307``.bootloader'' 5308 Defines the bootloader portion of the ROM (if applicable). Any 5309 code in this section will be uploaded to the MPU. 5310 5311``.infomem'' 5312 Defines an information memory section (if applicable). Any code in 5313 this section will be uploaded to the MPU. 5314 5315``.infomemnobits'' 5316 This is the same as the `.infomem' section except that any code in 5317 this section will not be uploaded to the MPU. 5318 5319``.noinit'' 5320 Denotes a portion of RAM located above `.bss' section. 5321 5322 The last two sections are used by gcc. 5323 5324 5325File: ld.info, Node: PowerPC ELF32, Next: PowerPC64 ELF64, Prev: M68HC11/68HC12, Up: Machine Dependent 5326 53274.9 `ld' and PowerPC 32-bit ELF Support 5328======================================= 5329 5330Branches on PowerPC processors are limited to a signed 26-bit 5331displacement, which may result in `ld' giving `relocation truncated to 5332fit' errors with very large programs. `--relax' enables the generation 5333of trampolines that can access the entire 32-bit address space. These 5334trampolines are inserted at section boundaries, so may not themselves 5335be reachable if an input section exceeds 33M in size. You may combine 5336`-r' and `--relax' to add trampolines in a partial link. In that case 5337both branches to undefined symbols and inter-section branches are also 5338considered potentially out of range, and trampolines inserted. 5339 5340`--bss-plt' 5341 Current PowerPC GCC accepts a `-msecure-plt' option that generates 5342 code capable of using a newer PLT and GOT layout that has the 5343 security advantage of no executable section ever needing to be 5344 writable and no writable section ever being executable. PowerPC 5345 `ld' will generate this layout, including stubs to access the PLT, 5346 if all input files (including startup and static libraries) were 5347 compiled with `-msecure-plt'. `--bss-plt' forces the old BSS PLT 5348 (and GOT layout) which can give slightly better performance. 5349 5350`--secure-plt' 5351 `ld' will use the new PLT and GOT layout if it is linking new 5352 `-fpic' or `-fPIC' code, but does not do so automatically when 5353 linking non-PIC code. This option requests the new PLT and GOT 5354 layout. A warning will be given if some object file requires the 5355 old style BSS PLT. 5356 5357`--sdata-got' 5358 The new secure PLT and GOT are placed differently relative to other 5359 sections compared to older BSS PLT and GOT placement. The 5360 location of `.plt' must change because the new secure PLT is an 5361 initialized section while the old PLT is uninitialized. The 5362 reason for the `.got' change is more subtle: The new placement 5363 allows `.got' to be read-only in applications linked with `-z 5364 relro -z now'. However, this placement means that `.sdata' cannot 5365 always be used in shared libraries, because the PowerPC ABI 5366 accesses `.sdata' in shared libraries from the GOT pointer. 5367 `--sdata-got' forces the old GOT placement. PowerPC GCC doesn't 5368 use `.sdata' in shared libraries, so this option is really only 5369 useful for other compilers that may do so. 5370 5371`--emit-stub-syms' 5372 This option causes `ld' to label linker stubs with a local symbol 5373 that encodes the stub type and destination. 5374 5375`--no-tls-optimize' 5376 PowerPC `ld' normally performs some optimization of code sequences 5377 used to access Thread-Local Storage. Use this option to disable 5378 the optimization. 5379 5380 5381File: ld.info, Node: PowerPC64 ELF64, Next: SPU ELF, Prev: PowerPC ELF32, Up: Machine Dependent 5382 53834.10 `ld' and PowerPC64 64-bit ELF Support 5384========================================== 5385 5386`--stub-group-size' 5387 Long branch stubs, PLT call stubs and TOC adjusting stubs are 5388 placed by `ld' in stub sections located between groups of input 5389 sections. `--stub-group-size' specifies the maximum size of a 5390 group of input sections handled by one stub section. Since branch 5391 offsets are signed, a stub section may serve two groups of input 5392 sections, one group before the stub section, and one group after 5393 it. However, when using conditional branches that require stubs, 5394 it may be better (for branch prediction) that stub sections only 5395 serve one group of input sections. A negative value for `N' 5396 chooses this scheme, ensuring that branches to stubs always use a 5397 negative offset. Two special values of `N' are recognized, `1' 5398 and `-1'. These both instruct `ld' to automatically size input 5399 section groups for the branch types detected, with the same 5400 behaviour regarding stub placement as other positive or negative 5401 values of `N' respectively. 5402 5403 Note that `--stub-group-size' does not split input sections. A 5404 single input section larger than the group size specified will of 5405 course create a larger group (of one section). If input sections 5406 are too large, it may not be possible for a branch to reach its 5407 stub. 5408 5409`--emit-stub-syms' 5410 This option causes `ld' to label linker stubs with a local symbol 5411 that encodes the stub type and destination. 5412 5413`--dotsyms, --no-dotsyms' 5414 These two options control how `ld' interprets version patterns in 5415 a version script. Older PowerPC64 compilers emitted both a 5416 function descriptor symbol with the same name as the function, and 5417 a code entry symbol with the name prefixed by a dot (`.'). To 5418 properly version a function `foo', the version script thus needs 5419 to control both `foo' and `.foo'. The option `--dotsyms', on by 5420 default, automatically adds the required dot-prefixed patterns. 5421 Use `--no-dotsyms' to disable this feature. 5422 5423`--no-tls-optimize' 5424 PowerPC64 `ld' normally performs some optimization of code 5425 sequences used to access Thread-Local Storage. Use this option to 5426 disable the optimization. 5427 5428`--no-opd-optimize' 5429 PowerPC64 `ld' normally removes `.opd' section entries 5430 corresponding to deleted link-once functions, or functions removed 5431 by the action of `--gc-sections' or linker script `/DISCARD/'. 5432 Use this option to disable `.opd' optimization. 5433 5434`--non-overlapping-opd' 5435 Some PowerPC64 compilers have an option to generate compressed 5436 `.opd' entries spaced 16 bytes apart, overlapping the third word, 5437 the static chain pointer (unused in C) with the first word of the 5438 next entry. This option expands such entries to the full 24 bytes. 5439 5440`--no-toc-optimize' 5441 PowerPC64 `ld' normally removes unused `.toc' section entries. 5442 Such entries are detected by examining relocations that reference 5443 the TOC in code sections. A reloc in a deleted code section marks 5444 a TOC word as unneeded, while a reloc in a kept code section marks 5445 a TOC word as needed. Since the TOC may reference itself, TOC 5446 relocs are also examined. TOC words marked as both needed and 5447 unneeded will of course be kept. TOC words without any referencing 5448 reloc are assumed to be part of a multi-word entry, and are kept or 5449 discarded as per the nearest marked preceding word. This works 5450 reliably for compiler generated code, but may be incorrect if 5451 assembly code is used to insert TOC entries. Use this option to 5452 disable the optimization. 5453 5454`--no-multi-toc' 5455 By default, PowerPC64 GCC generates code for a TOC model where TOC 5456 entries are accessed with a 16-bit offset from r2. This limits the 5457 total TOC size to 64K. PowerPC64 `ld' extends this limit by 5458 grouping code sections such that each group uses less than 64K for 5459 its TOC entries, then inserts r2 adjusting stubs between 5460 inter-group calls. `ld' does not split apart input sections, so 5461 cannot help if a single input file has a `.toc' section that 5462 exceeds 64K, most likely from linking multiple files with `ld -r'. 5463 Use this option to turn off this feature. 5464 5465 5466File: ld.info, Node: SPU ELF, Next: TI COFF, Prev: PowerPC64 ELF64, Up: Machine Dependent 5467 54684.11 `ld' and SPU ELF Support 5469============================= 5470 5471`--plugin' 5472 This option marks an executable as a PIC plugin module. 5473 5474`--no-overlays' 5475 Normally, `ld' recognizes calls to functions within overlay 5476 regions, and redirects such calls to an overlay manager via a stub. 5477 `ld' also provides a built-in overlay manager. This option turns 5478 off all this special overlay handling. 5479 5480`--emit-stub-syms' 5481 This option causes `ld' to label overlay stubs with a local symbol 5482 that encodes the stub type and destination. 5483 5484`--extra-overlay-stubs' 5485 This option causes `ld' to add overlay call stubs on all function 5486 calls out of overlay regions. Normally stubs are not added on 5487 calls to non-overlay regions. 5488 5489`--local-store=lo:hi' 5490 `ld' usually checks that a final executable for SPU fits in the 5491 address range 0 to 256k. This option may be used to change the 5492 range. Disable the check entirely with `--local-store=0:0'. 5493 5494`--stack-analysis' 5495 SPU local store space is limited. Over-allocation of stack space 5496 unnecessarily limits space available for code and data, while 5497 under-allocation results in runtime failures. If given this 5498 option, `ld' will provide an estimate of maximum stack usage. 5499 `ld' does this by examining symbols in code sections to determine 5500 the extents of functions, and looking at function prologues for 5501 stack adjusting instructions. A call-graph is created by looking 5502 for relocations on branch instructions. The graph is then searched 5503 for the maximum stack usage path. Note that this analysis does not 5504 find calls made via function pointers, and does not handle 5505 recursion and other cycles in the call graph. Stack usage may be 5506 under-estimated if your code makes such calls. Also, stack usage 5507 for dynamic allocation, e.g. alloca, will not be detected. If a 5508 link map is requested, detailed information about each function's 5509 stack usage and calls will be given. 5510 5511`--emit-stack-syms' 5512 This option, if given along with `--stack-analysis' will result in 5513 `ld' emitting stack sizing symbols for each function. These take 5514 the form `__stack_<function_name>' for global functions, and 5515 `__stack_<number>_<function_name>' for static functions. 5516 `<number>' is the section id in hex. The value of such symbols is 5517 the stack requirement for the corresponding function. The symbol 5518 size will be zero, type `STT_NOTYPE', binding `STB_LOCAL', and 5519 section `SHN_ABS'. 5520 5521 5522File: ld.info, Node: TI COFF, Next: WIN32, Prev: SPU ELF, Up: Machine Dependent 5523 55244.12 `ld''s Support for Various TI COFF Versions 5525================================================ 5526 5527The `--format' switch allows selection of one of the various TI COFF 5528versions. The latest of this writing is 2; versions 0 and 1 are also 5529supported. The TI COFF versions also vary in header byte-order format; 5530`ld' will read any version or byte order, but the output header format 5531depends on the default specified by the specific target. 5532 5533 5534File: ld.info, Node: WIN32, Next: Xtensa, Prev: TI COFF, Up: Machine Dependent 5535 55364.13 `ld' and WIN32 (cygwin/mingw) 5537================================== 5538 5539This section describes some of the win32 specific `ld' issues. See 5540*Note Command Line Options: Options. for detailed description of the 5541command line options mentioned here. 5542 5543_import libraries_ 5544 The standard Windows linker creates and uses so-called import 5545 libraries, which contains information for linking to dll's. They 5546 are regular static archives and are handled as any other static 5547 archive. The cygwin and mingw ports of `ld' have specific support 5548 for creating such libraries provided with the `--out-implib' 5549 command line option. 5550 5551_exporting DLL symbols_ 5552 The cygwin/mingw `ld' has several ways to export symbols for dll's. 5553 5554 _using auto-export functionality_ 5555 By default `ld' exports symbols with the auto-export 5556 functionality, which is controlled by the following command 5557 line options: 5558 5559 * -export-all-symbols [This is the default] 5560 5561 * -exclude-symbols 5562 5563 * -exclude-libs 5564 5565 * -exclude-modules-for-implib 5566 5567 * -version-script 5568 5569 When auto-export is in operation, `ld' will export all the 5570 non-local (global and common) symbols it finds in a DLL, with 5571 the exception of a few symbols known to belong to the 5572 system's runtime and libraries. As it will often not be 5573 desirable to export all of a DLL's symbols, which may include 5574 private functions that are not part of any public interface, 5575 the command-line options listed above may be used to filter 5576 symbols out from the list for exporting. The `--output-def' 5577 option can be used in order to see the final list of exported 5578 symbols with all exclusions taken into effect. 5579 5580 If `--export-all-symbols' is not given explicitly on the 5581 command line, then the default auto-export behavior will be 5582 _disabled_ if either of the following are true: 5583 5584 * A DEF file is used. 5585 5586 * Any symbol in any object file was marked with the 5587 __declspec(dllexport) attribute. 5588 5589 _using a DEF file_ 5590 Another way of exporting symbols is using a DEF file. A DEF 5591 file is an ASCII file containing definitions of symbols which 5592 should be exported when a dll is created. Usually it is 5593 named `<dll name>.def' and is added as any other object file 5594 to the linker's command line. The file's name must end in 5595 `.def' or `.DEF'. 5596 5597 gcc -o <output> <objectfiles> <dll name>.def 5598 5599 Using a DEF file turns off the normal auto-export behavior, 5600 unless the `--export-all-symbols' option is also used. 5601 5602 Here is an example of a DEF file for a shared library called 5603 `xyz.dll': 5604 5605 LIBRARY "xyz.dll" BASE=0x20000000 5606 5607 EXPORTS 5608 foo 5609 bar 5610 _bar = bar 5611 another_foo = abc.dll.afoo 5612 var1 DATA 5613 doo = foo == foo2 5614 eoo DATA == var1 5615 5616 This example defines a DLL with a non-default base address 5617 and seven symbols in the export table. The third exported 5618 symbol `_bar' is an alias for the second. The fourth symbol, 5619 `another_foo' is resolved by "forwarding" to another module 5620 and treating it as an alias for `afoo' exported from the DLL 5621 `abc.dll'. The final symbol `var1' is declared to be a data 5622 object. The `doo' symbol in export library is an alias of 5623 `foo', which gets the string name in export table `foo2'. The 5624 `eoo' symbol is an data export symbol, which gets in export 5625 table the name `var1'. 5626 5627 The optional `LIBRARY <name>' command indicates the _internal_ 5628 name of the output DLL. If `<name>' does not include a suffix, 5629 the default library suffix, `.DLL' is appended. 5630 5631 When the .DEF file is used to build an application, rather 5632 than a library, the `NAME <name>' command should be used 5633 instead of `LIBRARY'. If `<name>' does not include a suffix, 5634 the default executable suffix, `.EXE' is appended. 5635 5636 With either `LIBRARY <name>' or `NAME <name>' the optional 5637 specification `BASE = <number>' may be used to specify a 5638 non-default base address for the image. 5639 5640 If neither `LIBRARY <name>' nor `NAME <name>' is specified, 5641 or they specify an empty string, the internal name is the 5642 same as the filename specified on the command line. 5643 5644 The complete specification of an export symbol is: 5645 5646 EXPORTS 5647 ( ( ( <name1> [ = <name2> ] ) 5648 | ( <name1> = <module-name> . <external-name>)) 5649 [ @ <integer> ] [NONAME] [DATA] [CONSTANT] [PRIVATE] [== <name3>] ) * 5650 5651 Declares `<name1>' as an exported symbol from the DLL, or 5652 declares `<name1>' as an exported alias for `<name2>'; or 5653 declares `<name1>' as a "forward" alias for the symbol 5654 `<external-name>' in the DLL `<module-name>'. Optionally, 5655 the symbol may be exported by the specified ordinal 5656 `<integer>' alias. The optional `<name3>' is the to be used 5657 string in import/export table for the symbol. 5658 5659 The optional keywords that follow the declaration indicate: 5660 5661 `NONAME': Do not put the symbol name in the DLL's export 5662 table. It will still be exported by its ordinal alias 5663 (either the value specified by the .def specification or, 5664 otherwise, the value assigned by the linker). The symbol 5665 name, however, does remain visible in the import library (if 5666 any), unless `PRIVATE' is also specified. 5667 5668 `DATA': The symbol is a variable or object, rather than a 5669 function. The import lib will export only an indirect 5670 reference to `foo' as the symbol `_imp__foo' (ie, `foo' must 5671 be resolved as `*_imp__foo'). 5672 5673 `CONSTANT': Like `DATA', but put the undecorated `foo' as 5674 well as `_imp__foo' into the import library. Both refer to the 5675 read-only import address table's pointer to the variable, not 5676 to the variable itself. This can be dangerous. If the user 5677 code fails to add the `dllimport' attribute and also fails to 5678 explicitly add the extra indirection that the use of the 5679 attribute enforces, the application will behave unexpectedly. 5680 5681 `PRIVATE': Put the symbol in the DLL's export table, but do 5682 not put it into the static import library used to resolve 5683 imports at link time. The symbol can still be imported using 5684 the `LoadLibrary/GetProcAddress' API at runtime or by by 5685 using the GNU ld extension of linking directly to the DLL 5686 without an import library. 5687 5688 See ld/deffilep.y in the binutils sources for the full 5689 specification of other DEF file statements 5690 5691 While linking a shared dll, `ld' is able to create a DEF file 5692 with the `--output-def <file>' command line option. 5693 5694 _Using decorations_ 5695 Another way of marking symbols for export is to modify the 5696 source code itself, so that when building the DLL each symbol 5697 to be exported is declared as: 5698 5699 __declspec(dllexport) int a_variable 5700 __declspec(dllexport) void a_function(int with_args) 5701 5702 All such symbols will be exported from the DLL. If, however, 5703 any of the object files in the DLL contain symbols decorated 5704 in this way, then the normal auto-export behavior is 5705 disabled, unless the `--export-all-symbols' option is also 5706 used. 5707 5708 Note that object files that wish to access these symbols must 5709 _not_ decorate them with dllexport. Instead, they should use 5710 dllimport, instead: 5711 5712 __declspec(dllimport) int a_variable 5713 __declspec(dllimport) void a_function(int with_args) 5714 5715 This complicates the structure of library header files, 5716 because when included by the library itself the header must 5717 declare the variables and functions as dllexport, but when 5718 included by client code the header must declare them as 5719 dllimport. There are a number of idioms that are typically 5720 used to do this; often client code can omit the __declspec() 5721 declaration completely. See `--enable-auto-import' and 5722 `automatic data imports' for more information. 5723 5724_automatic data imports_ 5725 The standard Windows dll format supports data imports from dlls 5726 only by adding special decorations (dllimport/dllexport), which 5727 let the compiler produce specific assembler instructions to deal 5728 with this issue. This increases the effort necessary to port 5729 existing Un*x code to these platforms, especially for large c++ 5730 libraries and applications. The auto-import feature, which was 5731 initially provided by Paul Sokolovsky, allows one to omit the 5732 decorations to achieve a behavior that conforms to that on 5733 POSIX/Un*x platforms. This feature is enabled with the 5734 `--enable-auto-import' command-line option, although it is enabled 5735 by default on cygwin/mingw. The `--enable-auto-import' option 5736 itself now serves mainly to suppress any warnings that are 5737 ordinarily emitted when linked objects trigger the feature's use. 5738 5739 auto-import of variables does not always work flawlessly without 5740 additional assistance. Sometimes, you will see this message 5741 5742 "variable '<var>' can't be auto-imported. Please read the 5743 documentation for ld's `--enable-auto-import' for details." 5744 5745 The `--enable-auto-import' documentation explains why this error 5746 occurs, and several methods that can be used to overcome this 5747 difficulty. One of these methods is the _runtime pseudo-relocs_ 5748 feature, described below. 5749 5750 For complex variables imported from DLLs (such as structs or 5751 classes), object files typically contain a base address for the 5752 variable and an offset (_addend_) within the variable-to specify a 5753 particular field or public member, for instance. Unfortunately, 5754 the runtime loader used in win32 environments is incapable of 5755 fixing these references at runtime without the additional 5756 information supplied by dllimport/dllexport decorations. The 5757 standard auto-import feature described above is unable to resolve 5758 these references. 5759 5760 The `--enable-runtime-pseudo-relocs' switch allows these 5761 references to be resolved without error, while leaving the task of 5762 adjusting the references themselves (with their non-zero addends) 5763 to specialized code provided by the runtime environment. Recent 5764 versions of the cygwin and mingw environments and compilers 5765 provide this runtime support; older versions do not. However, the 5766 support is only necessary on the developer's platform; the 5767 compiled result will run without error on an older system. 5768 5769 `--enable-runtime-pseudo-relocs' is not the default; it must be 5770 explicitly enabled as needed. 5771 5772_direct linking to a dll_ 5773 The cygwin/mingw ports of `ld' support the direct linking, 5774 including data symbols, to a dll without the usage of any import 5775 libraries. This is much faster and uses much less memory than 5776 does the traditional import library method, especially when 5777 linking large libraries or applications. When `ld' creates an 5778 import lib, each function or variable exported from the dll is 5779 stored in its own bfd, even though a single bfd could contain many 5780 exports. The overhead involved in storing, loading, and 5781 processing so many bfd's is quite large, and explains the 5782 tremendous time, memory, and storage needed to link against 5783 particularly large or complex libraries when using import libs. 5784 5785 Linking directly to a dll uses no extra command-line switches 5786 other than `-L' and `-l', because `ld' already searches for a 5787 number of names to match each library. All that is needed from 5788 the developer's perspective is an understanding of this search, in 5789 order to force ld to select the dll instead of an import library. 5790 5791 For instance, when ld is called with the argument `-lxxx' it will 5792 attempt to find, in the first directory of its search path, 5793 5794 libxxx.dll.a 5795 xxx.dll.a 5796 libxxx.a 5797 xxx.lib 5798 cygxxx.dll (*) 5799 libxxx.dll 5800 xxx.dll 5801 5802 before moving on to the next directory in the search path. 5803 5804 (*) Actually, this is not `cygxxx.dll' but in fact is 5805 `<prefix>xxx.dll', where `<prefix>' is set by the `ld' option 5806 `--dll-search-prefix=<prefix>'. In the case of cygwin, the 5807 standard gcc spec file includes `--dll-search-prefix=cyg', so in 5808 effect we actually search for `cygxxx.dll'. 5809 5810 Other win32-based unix environments, such as mingw or pw32, may 5811 use other `<prefix>'es, although at present only cygwin makes use 5812 of this feature. It was originally intended to help avoid name 5813 conflicts among dll's built for the various win32/un*x 5814 environments, so that (for example) two versions of a zlib dll 5815 could coexist on the same machine. 5816 5817 The generic cygwin/mingw path layout uses a `bin' directory for 5818 applications and dll's and a `lib' directory for the import 5819 libraries (using cygwin nomenclature): 5820 5821 bin/ 5822 cygxxx.dll 5823 lib/ 5824 libxxx.dll.a (in case of dll's) 5825 libxxx.a (in case of static archive) 5826 5827 Linking directly to a dll without using the import library can be 5828 done two ways: 5829 5830 1. Use the dll directly by adding the `bin' path to the link line 5831 gcc -Wl,-verbose -o a.exe -L../bin/ -lxxx 5832 5833 However, as the dll's often have version numbers appended to their 5834 names (`cygncurses-5.dll') this will often fail, unless one 5835 specifies `-L../bin -lncurses-5' to include the version. Import 5836 libs are generally not versioned, and do not have this difficulty. 5837 5838 2. Create a symbolic link from the dll to a file in the `lib' 5839 directory according to the above mentioned search pattern. This 5840 should be used to avoid unwanted changes in the tools needed for 5841 making the app/dll. 5842 5843 ln -s bin/cygxxx.dll lib/[cyg|lib|]xxx.dll[.a] 5844 5845 Then you can link without any make environment changes. 5846 5847 gcc -Wl,-verbose -o a.exe -L../lib/ -lxxx 5848 5849 This technique also avoids the version number problems, because 5850 the following is perfectly legal 5851 5852 bin/ 5853 cygxxx-5.dll 5854 lib/ 5855 libxxx.dll.a -> ../bin/cygxxx-5.dll 5856 5857 Linking directly to a dll without using an import lib will work 5858 even when auto-import features are exercised, and even when 5859 `--enable-runtime-pseudo-relocs' is used. 5860 5861 Given the improvements in speed and memory usage, one might 5862 justifiably wonder why import libraries are used at all. There 5863 are three reasons: 5864 5865 1. Until recently, the link-directly-to-dll functionality did _not_ 5866 work with auto-imported data. 5867 5868 2. Sometimes it is necessary to include pure static objects within 5869 the import library (which otherwise contains only bfd's for 5870 indirection symbols that point to the exports of a dll). Again, 5871 the import lib for the cygwin kernel makes use of this ability, 5872 and it is not possible to do this without an import lib. 5873 5874 3. Symbol aliases can only be resolved using an import lib. This 5875 is critical when linking against OS-supplied dll's (eg, the win32 5876 API) in which symbols are usually exported as undecorated aliases 5877 of their stdcall-decorated assembly names. 5878 5879 So, import libs are not going away. But the ability to replace 5880 true import libs with a simple symbolic link to (or a copy of) a 5881 dll, in many cases, is a useful addition to the suite of tools 5882 binutils makes available to the win32 developer. Given the 5883 massive improvements in memory requirements during linking, storage 5884 requirements, and linking speed, we expect that many developers 5885 will soon begin to use this feature whenever possible. 5886 5887_symbol aliasing_ 5888 5889 _adding additional names_ 5890 Sometimes, it is useful to export symbols with additional 5891 names. A symbol `foo' will be exported as `foo', but it can 5892 also be exported as `_foo' by using special directives in the 5893 DEF file when creating the dll. This will affect also the 5894 optional created import library. Consider the following DEF 5895 file: 5896 5897 LIBRARY "xyz.dll" BASE=0x61000000 5898 5899 EXPORTS 5900 foo 5901 _foo = foo 5902 5903 The line `_foo = foo' maps the symbol `foo' to `_foo'. 5904 5905 Another method for creating a symbol alias is to create it in 5906 the source code using the "weak" attribute: 5907 5908 void foo () { /* Do something. */; } 5909 void _foo () __attribute__ ((weak, alias ("foo"))); 5910 5911 See the gcc manual for more information about attributes and 5912 weak symbols. 5913 5914 _renaming symbols_ 5915 Sometimes it is useful to rename exports. For instance, the 5916 cygwin kernel does this regularly. A symbol `_foo' can be 5917 exported as `foo' but not as `_foo' by using special 5918 directives in the DEF file. (This will also affect the import 5919 library, if it is created). In the following example: 5920 5921 LIBRARY "xyz.dll" BASE=0x61000000 5922 5923 EXPORTS 5924 _foo = foo 5925 5926 The line `_foo = foo' maps the exported symbol `foo' to 5927 `_foo'. 5928 5929 Note: using a DEF file disables the default auto-export behavior, 5930 unless the `--export-all-symbols' command line option is used. 5931 If, however, you are trying to rename symbols, then you should list 5932 _all_ desired exports in the DEF file, including the symbols that 5933 are not being renamed, and do _not_ use the `--export-all-symbols' 5934 option. If you list only the renamed symbols in the DEF file, and 5935 use `--export-all-symbols' to handle the other symbols, then the 5936 both the new names _and_ the original names for the renamed 5937 symbols will be exported. In effect, you'd be aliasing those 5938 symbols, not renaming them, which is probably not what you wanted. 5939 5940_weak externals_ 5941 The Windows object format, PE, specifies a form of weak symbols 5942 called weak externals. When a weak symbol is linked and the 5943 symbol is not defined, the weak symbol becomes an alias for some 5944 other symbol. There are three variants of weak externals: 5945 * Definition is searched for in objects and libraries, 5946 historically called lazy externals. 5947 5948 * Definition is searched for only in other objects, not in 5949 libraries. This form is not presently implemented. 5950 5951 * No search; the symbol is an alias. This form is not presently 5952 implemented. 5953 As a GNU extension, weak symbols that do not specify an alternate 5954 symbol are supported. If the symbol is undefined when linking, 5955 the symbol uses a default value. 5956 5957_aligned common symbols_ 5958 As a GNU extension to the PE file format, it is possible to 5959 specify the desired alignment for a common symbol. This 5960 information is conveyed from the assembler or compiler to the 5961 linker by means of GNU-specific commands carried in the object 5962 file's `.drectve' section, which are recognized by `ld' and 5963 respected when laying out the common symbols. Native tools will 5964 be able to process object files employing this GNU extension, but 5965 will fail to respect the alignment instructions, and may issue 5966 noisy warnings about unknown linker directives. 5967 5968 5969File: ld.info, Node: Xtensa, Prev: WIN32, Up: Machine Dependent 5970 59714.14 `ld' and Xtensa Processors 5972=============================== 5973 5974The default `ld' behavior for Xtensa processors is to interpret 5975`SECTIONS' commands so that lists of explicitly named sections in a 5976specification with a wildcard file will be interleaved when necessary to 5977keep literal pools within the range of PC-relative load offsets. For 5978example, with the command: 5979 5980 SECTIONS 5981 { 5982 .text : { 5983 *(.literal .text) 5984 } 5985 } 5986 5987`ld' may interleave some of the `.literal' and `.text' sections from 5988different object files to ensure that the literal pools are within the 5989range of PC-relative load offsets. A valid interleaving might place 5990the `.literal' sections from an initial group of files followed by the 5991`.text' sections of that group of files. Then, the `.literal' sections 5992from the rest of the files and the `.text' sections from the rest of 5993the files would follow. 5994 5995 Relaxation is enabled by default for the Xtensa version of `ld' and 5996provides two important link-time optimizations. The first optimization 5997is to combine identical literal values to reduce code size. A redundant 5998literal will be removed and all the `L32R' instructions that use it 5999will be changed to reference an identical literal, as long as the 6000location of the replacement literal is within the offset range of all 6001the `L32R' instructions. The second optimization is to remove 6002unnecessary overhead from assembler-generated "longcall" sequences of 6003`L32R'/`CALLXN' when the target functions are within range of direct 6004`CALLN' instructions. 6005 6006 For each of these cases where an indirect call sequence can be 6007optimized to a direct call, the linker will change the `CALLXN' 6008instruction to a `CALLN' instruction, remove the `L32R' instruction, 6009and remove the literal referenced by the `L32R' instruction if it is 6010not used for anything else. Removing the `L32R' instruction always 6011reduces code size but can potentially hurt performance by changing the 6012alignment of subsequent branch targets. By default, the linker will 6013always preserve alignments, either by switching some instructions 6014between 24-bit encodings and the equivalent density instructions or by 6015inserting a no-op in place of the `L32R' instruction that was removed. 6016If code size is more important than performance, the `--size-opt' 6017option can be used to prevent the linker from widening density 6018instructions or inserting no-ops, except in a few cases where no-ops 6019are required for correctness. 6020 6021 The following Xtensa-specific command-line options can be used to 6022control the linker: 6023 6024`--size-opt' 6025 When optimizing indirect calls to direct calls, optimize for code 6026 size more than performance. With this option, the linker will not 6027 insert no-ops or widen density instructions to preserve branch 6028 target alignment. There may still be some cases where no-ops are 6029 required to preserve the correctness of the code. 6030 6031 6032File: ld.info, Node: BFD, Next: Reporting Bugs, Prev: Machine Dependent, Up: Top 6033 60345 BFD 6035***** 6036 6037The linker accesses object and archive files using the BFD libraries. 6038These libraries allow the linker to use the same routines to operate on 6039object files whatever the object file format. A different object file 6040format can be supported simply by creating a new BFD back end and adding 6041it to the library. To conserve runtime memory, however, the linker and 6042associated tools are usually configured to support only a subset of the 6043object file formats available. You can use `objdump -i' (*note 6044objdump: (binutils.info)objdump.) to list all the formats available for 6045your configuration. 6046 6047 As with most implementations, BFD is a compromise between several 6048conflicting requirements. The major factor influencing BFD design was 6049efficiency: any time used converting between formats is time which 6050would not have been spent had BFD not been involved. This is partly 6051offset by abstraction payback; since BFD simplifies applications and 6052back ends, more time and care may be spent optimizing algorithms for a 6053greater speed. 6054 6055 One minor artifact of the BFD solution which you should bear in mind 6056is the potential for information loss. There are two places where 6057useful information can be lost using the BFD mechanism: during 6058conversion and during output. *Note BFD information loss::. 6059 6060* Menu: 6061 6062* BFD outline:: How it works: an outline of BFD 6063 6064 6065File: ld.info, Node: BFD outline, Up: BFD 6066 60675.1 How It Works: An Outline of BFD 6068=================================== 6069 6070When an object file is opened, BFD subroutines automatically determine 6071the format of the input object file. They then build a descriptor in 6072memory with pointers to routines that will be used to access elements of 6073the object file's data structures. 6074 6075 As different information from the object files is required, BFD 6076reads from different sections of the file and processes them. For 6077example, a very common operation for the linker is processing symbol 6078tables. Each BFD back end provides a routine for converting between 6079the object file's representation of symbols and an internal canonical 6080format. When the linker asks for the symbol table of an object file, it 6081calls through a memory pointer to the routine from the relevant BFD 6082back end which reads and converts the table into a canonical form. The 6083linker then operates upon the canonical form. When the link is finished 6084and the linker writes the output file's symbol table, another BFD back 6085end routine is called to take the newly created symbol table and 6086convert it into the chosen output format. 6087 6088* Menu: 6089 6090* BFD information loss:: Information Loss 6091* Canonical format:: The BFD canonical object-file format 6092 6093 6094File: ld.info, Node: BFD information loss, Next: Canonical format, Up: BFD outline 6095 60965.1.1 Information Loss 6097---------------------- 6098 6099_Information can be lost during output._ The output formats supported 6100by BFD do not provide identical facilities, and information which can 6101be described in one form has nowhere to go in another format. One 6102example of this is alignment information in `b.out'. There is nowhere 6103in an `a.out' format file to store alignment information on the 6104contained data, so when a file is linked from `b.out' and an `a.out' 6105image is produced, alignment information will not propagate to the 6106output file. (The linker will still use the alignment information 6107internally, so the link is performed correctly). 6108 6109 Another example is COFF section names. COFF files may contain an 6110unlimited number of sections, each one with a textual section name. If 6111the target of the link is a format which does not have many sections 6112(e.g., `a.out') or has sections without names (e.g., the Oasys format), 6113the link cannot be done simply. You can circumvent this problem by 6114describing the desired input-to-output section mapping with the linker 6115command language. 6116 6117 _Information can be lost during canonicalization._ The BFD internal 6118canonical form of the external formats is not exhaustive; there are 6119structures in input formats for which there is no direct representation 6120internally. This means that the BFD back ends cannot maintain all 6121possible data richness through the transformation between external to 6122internal and back to external formats. 6123 6124 This limitation is only a problem when an application reads one 6125format and writes another. Each BFD back end is responsible for 6126maintaining as much data as possible, and the internal BFD canonical 6127form has structures which are opaque to the BFD core, and exported only 6128to the back ends. When a file is read in one format, the canonical form 6129is generated for BFD and the application. At the same time, the back 6130end saves away any information which may otherwise be lost. If the data 6131is then written back in the same format, the back end routine will be 6132able to use the canonical form provided by the BFD core as well as the 6133information it prepared earlier. Since there is a great deal of 6134commonality between back ends, there is no information lost when 6135linking or copying big endian COFF to little endian COFF, or `a.out' to 6136`b.out'. When a mixture of formats is linked, the information is only 6137lost from the files whose format differs from the destination. 6138 6139 6140File: ld.info, Node: Canonical format, Prev: BFD information loss, Up: BFD outline 6141 61425.1.2 The BFD canonical object-file format 6143------------------------------------------ 6144 6145The greatest potential for loss of information occurs when there is the 6146least overlap between the information provided by the source format, 6147that stored by the canonical format, and that needed by the destination 6148format. A brief description of the canonical form may help you 6149understand which kinds of data you can count on preserving across 6150conversions. 6151 6152_files_ 6153 Information stored on a per-file basis includes target machine 6154 architecture, particular implementation format type, a demand 6155 pageable bit, and a write protected bit. Information like Unix 6156 magic numbers is not stored here--only the magic numbers' meaning, 6157 so a `ZMAGIC' file would have both the demand pageable bit and the 6158 write protected text bit set. The byte order of the target is 6159 stored on a per-file basis, so that big- and little-endian object 6160 files may be used with one another. 6161 6162_sections_ 6163 Each section in the input file contains the name of the section, 6164 the section's original address in the object file, size and 6165 alignment information, various flags, and pointers into other BFD 6166 data structures. 6167 6168_symbols_ 6169 Each symbol contains a pointer to the information for the object 6170 file which originally defined it, its name, its value, and various 6171 flag bits. When a BFD back end reads in a symbol table, it 6172 relocates all symbols to make them relative to the base of the 6173 section where they were defined. Doing this ensures that each 6174 symbol points to its containing section. Each symbol also has a 6175 varying amount of hidden private data for the BFD back end. Since 6176 the symbol points to the original file, the private data format 6177 for that symbol is accessible. `ld' can operate on a collection 6178 of symbols of wildly different formats without problems. 6179 6180 Normal global and simple local symbols are maintained on output, 6181 so an output file (no matter its format) will retain symbols 6182 pointing to functions and to global, static, and common variables. 6183 Some symbol information is not worth retaining; in `a.out', type 6184 information is stored in the symbol table as long symbol names. 6185 This information would be useless to most COFF debuggers; the 6186 linker has command line switches to allow users to throw it away. 6187 6188 There is one word of type information within the symbol, so if the 6189 format supports symbol type information within symbols (for 6190 example, COFF, IEEE, Oasys) and the type is simple enough to fit 6191 within one word (nearly everything but aggregates), the 6192 information will be preserved. 6193 6194_relocation level_ 6195 Each canonical BFD relocation record contains a pointer to the 6196 symbol to relocate to, the offset of the data to relocate, the 6197 section the data is in, and a pointer to a relocation type 6198 descriptor. Relocation is performed by passing messages through 6199 the relocation type descriptor and the symbol pointer. Therefore, 6200 relocations can be performed on output data using a relocation 6201 method that is only available in one of the input formats. For 6202 instance, Oasys provides a byte relocation format. A relocation 6203 record requesting this relocation type would point indirectly to a 6204 routine to perform this, so the relocation may be performed on a 6205 byte being written to a 68k COFF file, even though 68k COFF has no 6206 such relocation type. 6207 6208_line numbers_ 6209 Object formats can contain, for debugging purposes, some form of 6210 mapping between symbols, source line numbers, and addresses in the 6211 output file. These addresses have to be relocated along with the 6212 symbol information. Each symbol with an associated list of line 6213 number records points to the first record of the list. The head 6214 of a line number list consists of a pointer to the symbol, which 6215 allows finding out the address of the function whose line number 6216 is being described. The rest of the list is made up of pairs: 6217 offsets into the section and line numbers. Any format which can 6218 simply derive this information can pass it successfully between 6219 formats (COFF, IEEE and Oasys). 6220 6221 6222File: ld.info, Node: Reporting Bugs, Next: MRI, Prev: BFD, Up: Top 6223 62246 Reporting Bugs 6225**************** 6226 6227Your bug reports play an essential role in making `ld' reliable. 6228 6229 Reporting a bug may help you by bringing a solution to your problem, 6230or it may not. But in any case the principal function of a bug report 6231is to help the entire community by making the next version of `ld' work 6232better. Bug reports are your contribution to the maintenance of `ld'. 6233 6234 In order for a bug report to serve its purpose, you must include the 6235information that enables us to fix the bug. 6236 6237* Menu: 6238 6239* Bug Criteria:: Have you found a bug? 6240* Bug Reporting:: How to report bugs 6241 6242 6243File: ld.info, Node: Bug Criteria, Next: Bug Reporting, Up: Reporting Bugs 6244 62456.1 Have You Found a Bug? 6246========================= 6247 6248If you are not sure whether you have found a bug, here are some 6249guidelines: 6250 6251 * If the linker gets a fatal signal, for any input whatever, that is 6252 a `ld' bug. Reliable linkers never crash. 6253 6254 * If `ld' produces an error message for valid input, that is a bug. 6255 6256 * If `ld' does not produce an error message for invalid input, that 6257 may be a bug. In the general case, the linker can not verify that 6258 object files are correct. 6259 6260 * If you are an experienced user of linkers, your suggestions for 6261 improvement of `ld' are welcome in any case. 6262 6263 6264File: ld.info, Node: Bug Reporting, Prev: Bug Criteria, Up: Reporting Bugs 6265 62666.2 How to Report Bugs 6267====================== 6268 6269A number of companies and individuals offer support for GNU products. 6270If you obtained `ld' from a support organization, we recommend you 6271contact that organization first. 6272 6273 You can find contact information for many support companies and 6274individuals in the file `etc/SERVICE' in the GNU Emacs distribution. 6275 6276 Otherwise, send bug reports for `ld' to 6277`http://www.sourceware.org/bugzilla/'. 6278 6279 The fundamental principle of reporting bugs usefully is this: 6280*report all the facts*. If you are not sure whether to state a fact or 6281leave it out, state it! 6282 6283 Often people omit facts because they think they know what causes the 6284problem and assume that some details do not matter. Thus, you might 6285assume that the name of a symbol you use in an example does not matter. 6286Well, probably it does not, but one cannot be sure. Perhaps the bug 6287is a stray memory reference which happens to fetch from the location 6288where that name is stored in memory; perhaps, if the name were 6289different, the contents of that location would fool the linker into 6290doing the right thing despite the bug. Play it safe and give a 6291specific, complete example. That is the easiest thing for you to do, 6292and the most helpful. 6293 6294 Keep in mind that the purpose of a bug report is to enable us to fix 6295the bug if it is new to us. Therefore, always write your bug reports 6296on the assumption that the bug has not been reported previously. 6297 6298 Sometimes people give a few sketchy facts and ask, "Does this ring a 6299bell?" This cannot help us fix a bug, so it is basically useless. We 6300respond by asking for enough details to enable us to investigate. You 6301might as well expedite matters by sending them to begin with. 6302 6303 To enable us to fix the bug, you should include all these things: 6304 6305 * The version of `ld'. `ld' announces it if you start it with the 6306 `--version' argument. 6307 6308 Without this, we will not know whether there is any point in 6309 looking for the bug in the current version of `ld'. 6310 6311 * Any patches you may have applied to the `ld' source, including any 6312 patches made to the `BFD' library. 6313 6314 * The type of machine you are using, and the operating system name 6315 and version number. 6316 6317 * What compiler (and its version) was used to compile `ld'--e.g. 6318 "`gcc-2.7'". 6319 6320 * The command arguments you gave the linker to link your example and 6321 observe the bug. To guarantee you will not omit something 6322 important, list them all. A copy of the Makefile (or the output 6323 from make) is sufficient. 6324 6325 If we were to try to guess the arguments, we would probably guess 6326 wrong and then we might not encounter the bug. 6327 6328 * A complete input file, or set of input files, that will reproduce 6329 the bug. It is generally most helpful to send the actual object 6330 files provided that they are reasonably small. Say no more than 6331 10K. For bigger files you can either make them available by FTP 6332 or HTTP or else state that you are willing to send the object 6333 file(s) to whomever requests them. (Note - your email will be 6334 going to a mailing list, so we do not want to clog it up with 6335 large attachments). But small attachments are best. 6336 6337 If the source files were assembled using `gas' or compiled using 6338 `gcc', then it may be OK to send the source files rather than the 6339 object files. In this case, be sure to say exactly what version of 6340 `gas' or `gcc' was used to produce the object files. Also say how 6341 `gas' or `gcc' were configured. 6342 6343 * A description of what behavior you observe that you believe is 6344 incorrect. For example, "It gets a fatal signal." 6345 6346 Of course, if the bug is that `ld' gets a fatal signal, then we 6347 will certainly notice it. But if the bug is incorrect output, we 6348 might not notice unless it is glaringly wrong. You might as well 6349 not give us a chance to make a mistake. 6350 6351 Even if the problem you experience is a fatal signal, you should 6352 still say so explicitly. Suppose something strange is going on, 6353 such as, your copy of `ld' is out of sync, or you have encountered 6354 a bug in the C library on your system. (This has happened!) Your 6355 copy might crash and ours would not. If you told us to expect a 6356 crash, then when ours fails to crash, we would know that the bug 6357 was not happening for us. If you had not told us to expect a 6358 crash, then we would not be able to draw any conclusion from our 6359 observations. 6360 6361 * If you wish to suggest changes to the `ld' source, send us context 6362 diffs, as generated by `diff' with the `-u', `-c', or `-p' option. 6363 Always send diffs from the old file to the new file. If you even 6364 discuss something in the `ld' source, refer to it by context, not 6365 by line number. 6366 6367 The line numbers in our development sources will not match those 6368 in your sources. Your line numbers would convey no useful 6369 information to us. 6370 6371 Here are some things that are not necessary: 6372 6373 * A description of the envelope of the bug. 6374 6375 Often people who encounter a bug spend a lot of time investigating 6376 which changes to the input file will make the bug go away and which 6377 changes will not affect it. 6378 6379 This is often time consuming and not very useful, because the way 6380 we will find the bug is by running a single example under the 6381 debugger with breakpoints, not by pure deduction from a series of 6382 examples. We recommend that you save your time for something else. 6383 6384 Of course, if you can find a simpler example to report _instead_ 6385 of the original one, that is a convenience for us. Errors in the 6386 output will be easier to spot, running under the debugger will take 6387 less time, and so on. 6388 6389 However, simplification is not vital; if you do not want to do 6390 this, report the bug anyway and send us the entire test case you 6391 used. 6392 6393 * A patch for the bug. 6394 6395 A patch for the bug does help us if it is a good one. But do not 6396 omit the necessary information, such as the test case, on the 6397 assumption that a patch is all we need. We might see problems 6398 with your patch and decide to fix the problem another way, or we 6399 might not understand it at all. 6400 6401 Sometimes with a program as complicated as `ld' it is very hard to 6402 construct an example that will make the program follow a certain 6403 path through the code. If you do not send us the example, we will 6404 not be able to construct one, so we will not be able to verify 6405 that the bug is fixed. 6406 6407 And if we cannot understand what bug you are trying to fix, or why 6408 your patch should be an improvement, we will not install it. A 6409 test case will help us to understand. 6410 6411 * A guess about what the bug is or what it depends on. 6412 6413 Such guesses are usually wrong. Even we cannot guess right about 6414 such things without first using the debugger to find the facts. 6415 6416 6417File: ld.info, Node: MRI, Next: GNU Free Documentation License, Prev: Reporting Bugs, Up: Top 6418 6419Appendix A MRI Compatible Script Files 6420************************************** 6421 6422To aid users making the transition to GNU `ld' from the MRI linker, 6423`ld' can use MRI compatible linker scripts as an alternative to the 6424more general-purpose linker scripting language described in *Note 6425Scripts::. MRI compatible linker scripts have a much simpler command 6426set than the scripting language otherwise used with `ld'. GNU `ld' 6427supports the most commonly used MRI linker commands; these commands are 6428described here. 6429 6430 In general, MRI scripts aren't of much use with the `a.out' object 6431file format, since it only has three sections and MRI scripts lack some 6432features to make use of them. 6433 6434 You can specify a file containing an MRI-compatible script using the 6435`-c' command-line option. 6436 6437 Each command in an MRI-compatible script occupies its own line; each 6438command line starts with the keyword that identifies the command (though 6439blank lines are also allowed for punctuation). If a line of an 6440MRI-compatible script begins with an unrecognized keyword, `ld' issues 6441a warning message, but continues processing the script. 6442 6443 Lines beginning with `*' are comments. 6444 6445 You can write these commands using all upper-case letters, or all 6446lower case; for example, `chip' is the same as `CHIP'. The following 6447list shows only the upper-case form of each command. 6448 6449`ABSOLUTE SECNAME' 6450`ABSOLUTE SECNAME, SECNAME, ... SECNAME' 6451 Normally, `ld' includes in the output file all sections from all 6452 the input files. However, in an MRI-compatible script, you can 6453 use the `ABSOLUTE' command to restrict the sections that will be 6454 present in your output program. If the `ABSOLUTE' command is used 6455 at all in a script, then only the sections named explicitly in 6456 `ABSOLUTE' commands will appear in the linker output. You can 6457 still use other input sections (whatever you select on the command 6458 line, or using `LOAD') to resolve addresses in the output file. 6459 6460`ALIAS OUT-SECNAME, IN-SECNAME' 6461 Use this command to place the data from input section IN-SECNAME 6462 in a section called OUT-SECNAME in the linker output file. 6463 6464 IN-SECNAME may be an integer. 6465 6466`ALIGN SECNAME = EXPRESSION' 6467 Align the section called SECNAME to EXPRESSION. The EXPRESSION 6468 should be a power of two. 6469 6470`BASE EXPRESSION' 6471 Use the value of EXPRESSION as the lowest address (other than 6472 absolute addresses) in the output file. 6473 6474`CHIP EXPRESSION' 6475`CHIP EXPRESSION, EXPRESSION' 6476 This command does nothing; it is accepted only for compatibility. 6477 6478`END' 6479 This command does nothing whatever; it's only accepted for 6480 compatibility. 6481 6482`FORMAT OUTPUT-FORMAT' 6483 Similar to the `OUTPUT_FORMAT' command in the more general linker 6484 language, but restricted to one of these output formats: 6485 6486 1. S-records, if OUTPUT-FORMAT is `S' 6487 6488 2. IEEE, if OUTPUT-FORMAT is `IEEE' 6489 6490 3. COFF (the `coff-m68k' variant in BFD), if OUTPUT-FORMAT is 6491 `COFF' 6492 6493`LIST ANYTHING...' 6494 Print (to the standard output file) a link map, as produced by the 6495 `ld' command-line option `-M'. 6496 6497 The keyword `LIST' may be followed by anything on the same line, 6498 with no change in its effect. 6499 6500`LOAD FILENAME' 6501`LOAD FILENAME, FILENAME, ... FILENAME' 6502 Include one or more object file FILENAME in the link; this has the 6503 same effect as specifying FILENAME directly on the `ld' command 6504 line. 6505 6506`NAME OUTPUT-NAME' 6507 OUTPUT-NAME is the name for the program produced by `ld'; the 6508 MRI-compatible command `NAME' is equivalent to the command-line 6509 option `-o' or the general script language command `OUTPUT'. 6510 6511`ORDER SECNAME, SECNAME, ... SECNAME' 6512`ORDER SECNAME SECNAME SECNAME' 6513 Normally, `ld' orders the sections in its output file in the order 6514 in which they first appear in the input files. In an 6515 MRI-compatible script, you can override this ordering with the 6516 `ORDER' command. The sections you list with `ORDER' will appear 6517 first in your output file, in the order specified. 6518 6519`PUBLIC NAME=EXPRESSION' 6520`PUBLIC NAME,EXPRESSION' 6521`PUBLIC NAME EXPRESSION' 6522 Supply a value (EXPRESSION) for external symbol NAME used in the 6523 linker input files. 6524 6525`SECT SECNAME, EXPRESSION' 6526`SECT SECNAME=EXPRESSION' 6527`SECT SECNAME EXPRESSION' 6528 You can use any of these three forms of the `SECT' command to 6529 specify the start address (EXPRESSION) for section SECNAME. If 6530 you have more than one `SECT' statement for the same SECNAME, only 6531 the _first_ sets the start address. 6532 6533 6534File: ld.info, Node: GNU Free Documentation License, Next: LD Index, Prev: MRI, Up: Top 6535 6536Appendix B GNU Free Documentation License 6537***************************************** 6538 6539 Version 1.3, 3 November 2008 6540 6541 Copyright (C) 2000, 2001, 2002, 2007, 2008 Free Software Foundation, Inc. 6542 `http://fsf.org/' 6543 6544 Everyone is permitted to copy and distribute verbatim copies 6545 of this license document, but changing it is not allowed. 6546 6547 0. PREAMBLE 6548 6549 The purpose of this License is to make a manual, textbook, or other 6550 functional and useful document "free" in the sense of freedom: to 6551 assure everyone the effective freedom to copy and redistribute it, 6552 with or without modifying it, either commercially or 6553 noncommercially. Secondarily, this License preserves for the 6554 author and publisher a way to get credit for their work, while not 6555 being considered responsible for modifications made by others. 6556 6557 This License is a kind of "copyleft", which means that derivative 6558 works of the document must themselves be free in the same sense. 6559 It complements the GNU General Public License, which is a copyleft 6560 license designed for free software. 6561 6562 We have designed this License in order to use it for manuals for 6563 free software, because free software needs free documentation: a 6564 free program should come with manuals providing the same freedoms 6565 that the software does. But this License is not limited to 6566 software manuals; it can be used for any textual work, regardless 6567 of subject matter or whether it is published as a printed book. 6568 We recommend this License principally for works whose purpose is 6569 instruction or reference. 6570 6571 1. APPLICABILITY AND DEFINITIONS 6572 6573 This License applies to any manual or other work, in any medium, 6574 that contains a notice placed by the copyright holder saying it 6575 can be distributed under the terms of this License. Such a notice 6576 grants a world-wide, royalty-free license, unlimited in duration, 6577 to use that work under the conditions stated herein. The 6578 "Document", below, refers to any such manual or work. Any member 6579 of the public is a licensee, and is addressed as "you". You 6580 accept the license if you copy, modify or distribute the work in a 6581 way requiring permission under copyright law. 6582 6583 A "Modified Version" of the Document means any work containing the 6584 Document or a portion of it, either copied verbatim, or with 6585 modifications and/or translated into another language. 6586 6587 A "Secondary Section" is a named appendix or a front-matter section 6588 of the Document that deals exclusively with the relationship of the 6589 publishers or authors of the Document to the Document's overall 6590 subject (or to related matters) and contains nothing that could 6591 fall directly within that overall subject. (Thus, if the Document 6592 is in part a textbook of mathematics, a Secondary Section may not 6593 explain any mathematics.) The relationship could be a matter of 6594 historical connection with the subject or with related matters, or 6595 of legal, commercial, philosophical, ethical or political position 6596 regarding them. 6597 6598 The "Invariant Sections" are certain Secondary Sections whose 6599 titles are designated, as being those of Invariant Sections, in 6600 the notice that says that the Document is released under this 6601 License. If a section does not fit the above definition of 6602 Secondary then it is not allowed to be designated as Invariant. 6603 The Document may contain zero Invariant Sections. If the Document 6604 does not identify any Invariant Sections then there are none. 6605 6606 The "Cover Texts" are certain short passages of text that are 6607 listed, as Front-Cover Texts or Back-Cover Texts, in the notice 6608 that says that the Document is released under this License. A 6609 Front-Cover Text may be at most 5 words, and a Back-Cover Text may 6610 be at most 25 words. 6611 6612 A "Transparent" copy of the Document means a machine-readable copy, 6613 represented in a format whose specification is available to the 6614 general public, that is suitable for revising the document 6615 straightforwardly with generic text editors or (for images 6616 composed of pixels) generic paint programs or (for drawings) some 6617 widely available drawing editor, and that is suitable for input to 6618 text formatters or for automatic translation to a variety of 6619 formats suitable for input to text formatters. A copy made in an 6620 otherwise Transparent file format whose markup, or absence of 6621 markup, has been arranged to thwart or discourage subsequent 6622 modification by readers is not Transparent. An image format is 6623 not Transparent if used for any substantial amount of text. A 6624 copy that is not "Transparent" is called "Opaque". 6625 6626 Examples of suitable formats for Transparent copies include plain 6627 ASCII without markup, Texinfo input format, LaTeX input format, 6628 SGML or XML using a publicly available DTD, and 6629 standard-conforming simple HTML, PostScript or PDF designed for 6630 human modification. Examples of transparent image formats include 6631 PNG, XCF and JPG. Opaque formats include proprietary formats that 6632 can be read and edited only by proprietary word processors, SGML or 6633 XML for which the DTD and/or processing tools are not generally 6634 available, and the machine-generated HTML, PostScript or PDF 6635 produced by some word processors for output purposes only. 6636 6637 The "Title Page" means, for a printed book, the title page itself, 6638 plus such following pages as are needed to hold, legibly, the 6639 material this License requires to appear in the title page. For 6640 works in formats which do not have any title page as such, "Title 6641 Page" means the text near the most prominent appearance of the 6642 work's title, preceding the beginning of the body of the text. 6643 6644 The "publisher" means any person or entity that distributes copies 6645 of the Document to the public. 6646 6647 A section "Entitled XYZ" means a named subunit of the Document 6648 whose title either is precisely XYZ or contains XYZ in parentheses 6649 following text that translates XYZ in another language. (Here XYZ 6650 stands for a specific section name mentioned below, such as 6651 "Acknowledgements", "Dedications", "Endorsements", or "History".) 6652 To "Preserve the Title" of such a section when you modify the 6653 Document means that it remains a section "Entitled XYZ" according 6654 to this definition. 6655 6656 The Document may include Warranty Disclaimers next to the notice 6657 which states that this License applies to the Document. These 6658 Warranty Disclaimers are considered to be included by reference in 6659 this License, but only as regards disclaiming warranties: any other 6660 implication that these Warranty Disclaimers may have is void and 6661 has no effect on the meaning of this License. 6662 6663 2. VERBATIM COPYING 6664 6665 You may copy and distribute the Document in any medium, either 6666 commercially or noncommercially, provided that this License, the 6667 copyright notices, and the license notice saying this License 6668 applies to the Document are reproduced in all copies, and that you 6669 add no other conditions whatsoever to those of this License. You 6670 may not use technical measures to obstruct or control the reading 6671 or further copying of the copies you make or distribute. However, 6672 you may accept compensation in exchange for copies. If you 6673 distribute a large enough number of copies you must also follow 6674 the conditions in section 3. 6675 6676 You may also lend copies, under the same conditions stated above, 6677 and you may publicly display copies. 6678 6679 3. COPYING IN QUANTITY 6680 6681 If you publish printed copies (or copies in media that commonly 6682 have printed covers) of the Document, numbering more than 100, and 6683 the Document's license notice requires Cover Texts, you must 6684 enclose the copies in covers that carry, clearly and legibly, all 6685 these Cover Texts: Front-Cover Texts on the front cover, and 6686 Back-Cover Texts on the back cover. Both covers must also clearly 6687 and legibly identify you as the publisher of these copies. The 6688 front cover must present the full title with all words of the 6689 title equally prominent and visible. You may add other material 6690 on the covers in addition. Copying with changes limited to the 6691 covers, as long as they preserve the title of the Document and 6692 satisfy these conditions, can be treated as verbatim copying in 6693 other respects. 6694 6695 If the required texts for either cover are too voluminous to fit 6696 legibly, you should put the first ones listed (as many as fit 6697 reasonably) on the actual cover, and continue the rest onto 6698 adjacent pages. 6699 6700 If you publish or distribute Opaque copies of the Document 6701 numbering more than 100, you must either include a 6702 machine-readable Transparent copy along with each Opaque copy, or 6703 state in or with each Opaque copy a computer-network location from 6704 which the general network-using public has access to download 6705 using public-standard network protocols a complete Transparent 6706 copy of the Document, free of added material. If you use the 6707 latter option, you must take reasonably prudent steps, when you 6708 begin distribution of Opaque copies in quantity, to ensure that 6709 this Transparent copy will remain thus accessible at the stated 6710 location until at least one year after the last time you 6711 distribute an Opaque copy (directly or through your agents or 6712 retailers) of that edition to the public. 6713 6714 It is requested, but not required, that you contact the authors of 6715 the Document well before redistributing any large number of 6716 copies, to give them a chance to provide you with an updated 6717 version of the Document. 6718 6719 4. MODIFICATIONS 6720 6721 You may copy and distribute a Modified Version of the Document 6722 under the conditions of sections 2 and 3 above, provided that you 6723 release the Modified Version under precisely this License, with 6724 the Modified Version filling the role of the Document, thus 6725 licensing distribution and modification of the Modified Version to 6726 whoever possesses a copy of it. In addition, you must do these 6727 things in the Modified Version: 6728 6729 A. Use in the Title Page (and on the covers, if any) a title 6730 distinct from that of the Document, and from those of 6731 previous versions (which should, if there were any, be listed 6732 in the History section of the Document). You may use the 6733 same title as a previous version if the original publisher of 6734 that version gives permission. 6735 6736 B. List on the Title Page, as authors, one or more persons or 6737 entities responsible for authorship of the modifications in 6738 the Modified Version, together with at least five of the 6739 principal authors of the Document (all of its principal 6740 authors, if it has fewer than five), unless they release you 6741 from this requirement. 6742 6743 C. State on the Title page the name of the publisher of the 6744 Modified Version, as the publisher. 6745 6746 D. Preserve all the copyright notices of the Document. 6747 6748 E. Add an appropriate copyright notice for your modifications 6749 adjacent to the other copyright notices. 6750 6751 F. Include, immediately after the copyright notices, a license 6752 notice giving the public permission to use the Modified 6753 Version under the terms of this License, in the form shown in 6754 the Addendum below. 6755 6756 G. Preserve in that license notice the full lists of Invariant 6757 Sections and required Cover Texts given in the Document's 6758 license notice. 6759 6760 H. Include an unaltered copy of this License. 6761 6762 I. Preserve the section Entitled "History", Preserve its Title, 6763 and add to it an item stating at least the title, year, new 6764 authors, and publisher of the Modified Version as given on 6765 the Title Page. If there is no section Entitled "History" in 6766 the Document, create one stating the title, year, authors, 6767 and publisher of the Document as given on its Title Page, 6768 then add an item describing the Modified Version as stated in 6769 the previous sentence. 6770 6771 J. Preserve the network location, if any, given in the Document 6772 for public access to a Transparent copy of the Document, and 6773 likewise the network locations given in the Document for 6774 previous versions it was based on. These may be placed in 6775 the "History" section. You may omit a network location for a 6776 work that was published at least four years before the 6777 Document itself, or if the original publisher of the version 6778 it refers to gives permission. 6779 6780 K. For any section Entitled "Acknowledgements" or "Dedications", 6781 Preserve the Title of the section, and preserve in the 6782 section all the substance and tone of each of the contributor 6783 acknowledgements and/or dedications given therein. 6784 6785 L. Preserve all the Invariant Sections of the Document, 6786 unaltered in their text and in their titles. Section numbers 6787 or the equivalent are not considered part of the section 6788 titles. 6789 6790 M. Delete any section Entitled "Endorsements". Such a section 6791 may not be included in the Modified Version. 6792 6793 N. Do not retitle any existing section to be Entitled 6794 "Endorsements" or to conflict in title with any Invariant 6795 Section. 6796 6797 O. Preserve any Warranty Disclaimers. 6798 6799 If the Modified Version includes new front-matter sections or 6800 appendices that qualify as Secondary Sections and contain no 6801 material copied from the Document, you may at your option 6802 designate some or all of these sections as invariant. To do this, 6803 add their titles to the list of Invariant Sections in the Modified 6804 Version's license notice. These titles must be distinct from any 6805 other section titles. 6806 6807 You may add a section Entitled "Endorsements", provided it contains 6808 nothing but endorsements of your Modified Version by various 6809 parties--for example, statements of peer review or that the text 6810 has been approved by an organization as the authoritative 6811 definition of a standard. 6812 6813 You may add a passage of up to five words as a Front-Cover Text, 6814 and a passage of up to 25 words as a Back-Cover Text, to the end 6815 of the list of Cover Texts in the Modified Version. Only one 6816 passage of Front-Cover Text and one of Back-Cover Text may be 6817 added by (or through arrangements made by) any one entity. If the 6818 Document already includes a cover text for the same cover, 6819 previously added by you or by arrangement made by the same entity 6820 you are acting on behalf of, you may not add another; but you may 6821 replace the old one, on explicit permission from the previous 6822 publisher that added the old one. 6823 6824 The author(s) and publisher(s) of the Document do not by this 6825 License give permission to use their names for publicity for or to 6826 assert or imply endorsement of any Modified Version. 6827 6828 5. COMBINING DOCUMENTS 6829 6830 You may combine the Document with other documents released under 6831 this License, under the terms defined in section 4 above for 6832 modified versions, provided that you include in the combination 6833 all of the Invariant Sections of all of the original documents, 6834 unmodified, and list them all as Invariant Sections of your 6835 combined work in its license notice, and that you preserve all 6836 their Warranty Disclaimers. 6837 6838 The combined work need only contain one copy of this License, and 6839 multiple identical Invariant Sections may be replaced with a single 6840 copy. If there are multiple Invariant Sections with the same name 6841 but different contents, make the title of each such section unique 6842 by adding at the end of it, in parentheses, the name of the 6843 original author or publisher of that section if known, or else a 6844 unique number. Make the same adjustment to the section titles in 6845 the list of Invariant Sections in the license notice of the 6846 combined work. 6847 6848 In the combination, you must combine any sections Entitled 6849 "History" in the various original documents, forming one section 6850 Entitled "History"; likewise combine any sections Entitled 6851 "Acknowledgements", and any sections Entitled "Dedications". You 6852 must delete all sections Entitled "Endorsements." 6853 6854 6. COLLECTIONS OF DOCUMENTS 6855 6856 You may make a collection consisting of the Document and other 6857 documents released under this License, and replace the individual 6858 copies of this License in the various documents with a single copy 6859 that is included in the collection, provided that you follow the 6860 rules of this License for verbatim copying of each of the 6861 documents in all other respects. 6862 6863 You may extract a single document from such a collection, and 6864 distribute it individually under this License, provided you insert 6865 a copy of this License into the extracted document, and follow 6866 this License in all other respects regarding verbatim copying of 6867 that document. 6868 6869 7. AGGREGATION WITH INDEPENDENT WORKS 6870 6871 A compilation of the Document or its derivatives with other 6872 separate and independent documents or works, in or on a volume of 6873 a storage or distribution medium, is called an "aggregate" if the 6874 copyright resulting from the compilation is not used to limit the 6875 legal rights of the compilation's users beyond what the individual 6876 works permit. When the Document is included in an aggregate, this 6877 License does not apply to the other works in the aggregate which 6878 are not themselves derivative works of the Document. 6879 6880 If the Cover Text requirement of section 3 is applicable to these 6881 copies of the Document, then if the Document is less than one half 6882 of the entire aggregate, the Document's Cover Texts may be placed 6883 on covers that bracket the Document within the aggregate, or the 6884 electronic equivalent of covers if the Document is in electronic 6885 form. Otherwise they must appear on printed covers that bracket 6886 the whole aggregate. 6887 6888 8. TRANSLATION 6889 6890 Translation is considered a kind of modification, so you may 6891 distribute translations of the Document under the terms of section 6892 4. Replacing Invariant Sections with translations requires special 6893 permission from their copyright holders, but you may include 6894 translations of some or all Invariant Sections in addition to the 6895 original versions of these Invariant Sections. You may include a 6896 translation of this License, and all the license notices in the 6897 Document, and any Warranty Disclaimers, provided that you also 6898 include the original English version of this License and the 6899 original versions of those notices and disclaimers. In case of a 6900 disagreement between the translation and the original version of 6901 this License or a notice or disclaimer, the original version will 6902 prevail. 6903 6904 If a section in the Document is Entitled "Acknowledgements", 6905 "Dedications", or "History", the requirement (section 4) to 6906 Preserve its Title (section 1) will typically require changing the 6907 actual title. 6908 6909 9. TERMINATION 6910 6911 You may not copy, modify, sublicense, or distribute the Document 6912 except as expressly provided under this License. Any attempt 6913 otherwise to copy, modify, sublicense, or distribute it is void, 6914 and will automatically terminate your rights under this License. 6915 6916 However, if you cease all violation of this License, then your 6917 license from a particular copyright holder is reinstated (a) 6918 provisionally, unless and until the copyright holder explicitly 6919 and finally terminates your license, and (b) permanently, if the 6920 copyright holder fails to notify you of the violation by some 6921 reasonable means prior to 60 days after the cessation. 6922 6923 Moreover, your license from a particular copyright holder is 6924 reinstated permanently if the copyright holder notifies you of the 6925 violation by some reasonable means, this is the first time you have 6926 received notice of violation of this License (for any work) from 6927 that copyright holder, and you cure the violation prior to 30 days 6928 after your receipt of the notice. 6929 6930 Termination of your rights under this section does not terminate 6931 the licenses of parties who have received copies or rights from 6932 you under this License. If your rights have been terminated and 6933 not permanently reinstated, receipt of a copy of some or all of 6934 the same material does not give you any rights to use it. 6935 6936 10. FUTURE REVISIONS OF THIS LICENSE 6937 6938 The Free Software Foundation may publish new, revised versions of 6939 the GNU Free Documentation License from time to time. Such new 6940 versions will be similar in spirit to the present version, but may 6941 differ in detail to address new problems or concerns. See 6942 `http://www.gnu.org/copyleft/'. 6943 6944 Each version of the License is given a distinguishing version 6945 number. If the Document specifies that a particular numbered 6946 version of this License "or any later version" applies to it, you 6947 have the option of following the terms and conditions either of 6948 that specified version or of any later version that has been 6949 published (not as a draft) by the Free Software Foundation. If 6950 the Document does not specify a version number of this License, 6951 you may choose any version ever published (not as a draft) by the 6952 Free Software Foundation. If the Document specifies that a proxy 6953 can decide which future versions of this License can be used, that 6954 proxy's public statement of acceptance of a version permanently 6955 authorizes you to choose that version for the Document. 6956 6957 11. RELICENSING 6958 6959 "Massive Multiauthor Collaboration Site" (or "MMC Site") means any 6960 World Wide Web server that publishes copyrightable works and also 6961 provides prominent facilities for anybody to edit those works. A 6962 public wiki that anybody can edit is an example of such a server. 6963 A "Massive Multiauthor Collaboration" (or "MMC") contained in the 6964 site means any set of copyrightable works thus published on the MMC 6965 site. 6966 6967 "CC-BY-SA" means the Creative Commons Attribution-Share Alike 3.0 6968 license published by Creative Commons Corporation, a not-for-profit 6969 corporation with a principal place of business in San Francisco, 6970 California, as well as future copyleft versions of that license 6971 published by that same organization. 6972 6973 "Incorporate" means to publish or republish a Document, in whole or 6974 in part, as part of another Document. 6975 6976 An MMC is "eligible for relicensing" if it is licensed under this 6977 License, and if all works that were first published under this 6978 License somewhere other than this MMC, and subsequently 6979 incorporated in whole or in part into the MMC, (1) had no cover 6980 texts or invariant sections, and (2) were thus incorporated prior 6981 to November 1, 2008. 6982 6983 The operator of an MMC Site may republish an MMC contained in the 6984 site under CC-BY-SA on the same site at any time before August 1, 6985 2009, provided the MMC is eligible for relicensing. 6986 6987 6988ADDENDUM: How to use this License for your documents 6989==================================================== 6990 6991To use this License in a document you have written, include a copy of 6992the License in the document and put the following copyright and license 6993notices just after the title page: 6994 6995 Copyright (C) YEAR YOUR NAME. 6996 Permission is granted to copy, distribute and/or modify this document 6997 under the terms of the GNU Free Documentation License, Version 1.3 6998 or any later version published by the Free Software Foundation; 6999 with no Invariant Sections, no Front-Cover Texts, and no Back-Cover 7000 Texts. A copy of the license is included in the section entitled ``GNU 7001 Free Documentation License''. 7002 7003 If you have Invariant Sections, Front-Cover Texts and Back-Cover 7004Texts, replace the "with...Texts." line with this: 7005 7006 with the Invariant Sections being LIST THEIR TITLES, with 7007 the Front-Cover Texts being LIST, and with the Back-Cover Texts 7008 being LIST. 7009 7010 If you have Invariant Sections without Cover Texts, or some other 7011combination of the three, merge those two alternatives to suit the 7012situation. 7013 7014 If your document contains nontrivial examples of program code, we 7015recommend releasing these examples in parallel under your choice of 7016free software license, such as the GNU General Public License, to 7017permit their use in free software. 7018 7019 7020File: ld.info, Node: LD Index, Prev: GNU Free Documentation License, Up: Top 7021 7022LD Index 7023******** 7024 7025[index] 7026* Menu: 7027 7028* ": Symbols. (line 6) 7029* -(: Options. (line 696) 7030* --accept-unknown-input-arch: Options. (line 714) 7031* --add-needed: Options. (line 738) 7032* --add-stdcall-alias: Options. (line 1573) 7033* --allow-multiple-definition: Options. (line 984) 7034* --allow-shlib-undefined: Options. (line 990) 7035* --architecture=ARCH: Options. (line 123) 7036* --as-needed: Options. (line 724) 7037* --audit AUDITLIB: Options. (line 112) 7038* --auxiliary=NAME: Options. (line 255) 7039* --bank-window: Options. (line 1982) 7040* --base-file: Options. (line 1578) 7041* --be8: ARM. (line 28) 7042* --bss-plt: PowerPC ELF32. (line 16) 7043* --build-id: Options. (line 1535) 7044* --build-id=STYLE: Options. (line 1535) 7045* --check-sections: Options. (line 817) 7046* --copy-dt-needed-entries: Options. (line 829) 7047* --cref: Options. (line 850) 7048* --default-imported-symver: Options. (line 1027) 7049* --default-script=SCRIPT: Options. (line 541) 7050* --default-symver: Options. (line 1023) 7051* --defsym=SYMBOL=EXP: Options. (line 878) 7052* --demangle[=STYLE]: Options. (line 891) 7053* --depaudit AUDITLIB: Options. (line 177) 7054* --disable-auto-image-base: Options. (line 1757) 7055* --disable-auto-import: Options. (line 1892) 7056* --disable-long-section-names: Options. (line 1588) 7057* --disable-new-dtags: Options. (line 1498) 7058* --disable-runtime-pseudo-reloc: Options. (line 1905) 7059* --disable-stdcall-fixup: Options. (line 1610) 7060* --discard-all: Options. (line 587) 7061* --discard-locals: Options. (line 591) 7062* --dll: Options. (line 1583) 7063* --dll-search-prefix: Options. (line 1763) 7064* --dotsyms: PowerPC64 ELF64. (line 33) 7065* --dynamic-linker=FILE: Options. (line 904) 7066* --dynamic-list-cpp-new: Options. (line 809) 7067* --dynamic-list-cpp-typeinfo: Options. (line 813) 7068* --dynamic-list-data: Options. (line 806) 7069* --dynamic-list=DYNAMIC-LIST-FILE: Options. (line 793) 7070* --dynamicbase: Options. (line 1941) 7071* --eh-frame-hdr: Options. (line 1494) 7072* --emit-relocs: Options. (line 476) 7073* --emit-stack-syms: SPU ELF. (line 46) 7074* --emit-stub-syms <1>: PowerPC ELF32. (line 47) 7075* --emit-stub-syms <2>: SPU ELF. (line 15) 7076* --emit-stub-syms: PowerPC64 ELF64. (line 29) 7077* --enable-auto-image-base: Options. (line 1749) 7078* --enable-auto-import: Options. (line 1772) 7079* --enable-extra-pe-debug: Options. (line 1910) 7080* --enable-long-section-names: Options. (line 1588) 7081* --enable-new-dtags: Options. (line 1498) 7082* --enable-runtime-pseudo-reloc: Options. (line 1897) 7083* --enable-stdcall-fixup: Options. (line 1610) 7084* --entry=ENTRY: Options. (line 187) 7085* --error-unresolved-symbols: Options. (line 1447) 7086* --exclude-all-symbols: Options. (line 1664) 7087* --exclude-libs: Options. (line 197) 7088* --exclude-modules-for-implib: Options. (line 208) 7089* --exclude-symbols: Options. (line 1658) 7090* --export-all-symbols: Options. (line 1634) 7091* --export-dynamic: Options. (line 221) 7092* --extra-overlay-stubs: SPU ELF. (line 19) 7093* --fatal-warnings: Options. (line 911) 7094* --file-alignment: Options. (line 1668) 7095* --filter=NAME: Options. (line 276) 7096* --fix-cortex-a8: i960. (line 39) 7097* --fix-v4bx: ARM. (line 49) 7098* --fix-v4bx-interworking: ARM. (line 62) 7099* --force-dynamic: Options. (line 485) 7100* --force-exe-suffix: Options. (line 916) 7101* --forceinteg: Options. (line 1946) 7102* --format=FORMAT: Options. (line 134) 7103* --format=VERSION: TI COFF. (line 6) 7104* --gc-sections: Options. (line 926) 7105* --got: Options. (line 1995) 7106* --got=TYPE: M68K. (line 6) 7107* --gpsize=VALUE: Options. (line 309) 7108* --hash-size=NUMBER: Options. (line 1507) 7109* --hash-style=STYLE: Options. (line 1515) 7110* --heap: Options. (line 1674) 7111* --help: Options. (line 957) 7112* --image-base: Options. (line 1681) 7113* --just-symbols=FILE: Options. (line 508) 7114* --kill-at: Options. (line 1690) 7115* --large-address-aware: Options. (line 1695) 7116* --leading-underscore: Options. (line 1628) 7117* --library-path=DIR: Options. (line 368) 7118* --library=NAMESPEC: Options. (line 335) 7119* --local-store=lo:hi: SPU ELF. (line 24) 7120* --major-image-version: Options. (line 1704) 7121* --major-os-version: Options. (line 1709) 7122* --major-subsystem-version: Options. (line 1713) 7123* --merge-exidx-entries: i960. (line 48) 7124* --minor-image-version: Options. (line 1718) 7125* --minor-os-version: Options. (line 1723) 7126* --minor-subsystem-version: Options. (line 1727) 7127* --mri-script=MRI-CMDFILE: Options. (line 158) 7128* --multi-subspace: HPPA ELF32. (line 6) 7129* --nmagic: Options. (line 439) 7130* --no-accept-unknown-input-arch: Options. (line 714) 7131* --no-add-needed: Options. (line 738) 7132* --no-allow-shlib-undefined: Options. (line 990) 7133* --no-as-needed: Options. (line 724) 7134* --no-bind: Options. (line 1960) 7135* --no-check-sections: Options. (line 817) 7136* --no-copy-dt-needed-entries: Options. (line 829) 7137* --no-define-common: Options. (line 862) 7138* --no-demangle: Options. (line 891) 7139* --no-dotsyms: PowerPC64 ELF64. (line 33) 7140* --no-enum-size-warning: ARM. (line 111) 7141* --no-export-dynamic: Options. (line 221) 7142* --no-fatal-warnings: Options. (line 911) 7143* --no-fix-cortex-a8: i960. (line 39) 7144* --no-gc-sections: Options. (line 926) 7145* --no-isolation: Options. (line 1953) 7146* --no-keep-memory: Options. (line 969) 7147* --no-leading-underscore: Options. (line 1628) 7148* --no-merge-exidx-entries: i960. (line 48) 7149* --no-multi-toc: PowerPC64 ELF64. (line 74) 7150* --no-omagic: Options. (line 454) 7151* --no-opd-optimize: PowerPC64 ELF64. (line 48) 7152* --no-overlays: SPU ELF. (line 9) 7153* --no-print-gc-sections: Options. (line 948) 7154* --no-seh: Options. (line 1956) 7155* --no-tls-optimize <1>: PowerPC ELF32. (line 51) 7156* --no-tls-optimize: PowerPC64 ELF64. (line 43) 7157* --no-toc-optimize: PowerPC64 ELF64. (line 60) 7158* --no-trampoline: Options. (line 1976) 7159* --no-undefined: Options. (line 976) 7160* --no-undefined-version: Options. (line 1018) 7161* --no-warn-mismatch: Options. (line 1031) 7162* --no-warn-search-mismatch: Options. (line 1040) 7163* --no-wchar-size-warning: ARM. (line 118) 7164* --no-whole-archive: Options. (line 1044) 7165* --noinhibit-exec: Options. (line 1048) 7166* --non-overlapping-opd: PowerPC64 ELF64. (line 54) 7167* --nxcompat: Options. (line 1949) 7168* --oformat=OUTPUT-FORMAT: Options. (line 1060) 7169* --omagic: Options. (line 445) 7170* --out-implib: Options. (line 1740) 7171* --output-def: Options. (line 1732) 7172* --output=OUTPUT: Options. (line 460) 7173* --pic-executable: Options. (line 1073) 7174* --pic-veneer: ARM. (line 124) 7175* --plugin: SPU ELF. (line 6) 7176* --print-gc-sections: Options. (line 948) 7177* --print-map: Options. (line 402) 7178* --reduce-memory-overheads: Options. (line 1521) 7179* --relax: Options. (line 1089) 7180* --relax on i960: i960. (line 31) 7181* --relax on PowerPC: PowerPC ELF32. (line 6) 7182* --relax on Xtensa: Xtensa. (line 27) 7183* --relocatable: Options. (line 489) 7184* --retain-symbols-file=FILENAME: Options. (line 1115) 7185* --script=SCRIPT: Options. (line 532) 7186* --sdata-got: PowerPC ELF32. (line 33) 7187* --section-alignment: Options. (line 1915) 7188* --section-start=SECTIONNAME=ORG: Options. (line 1271) 7189* --secure-plt: PowerPC ELF32. (line 26) 7190* --sort-common: Options. (line 1213) 7191* --sort-section=alignment: Options. (line 1228) 7192* --sort-section=name: Options. (line 1224) 7193* --split-by-file: Options. (line 1232) 7194* --split-by-reloc: Options. (line 1237) 7195* --stack: Options. (line 1921) 7196* --stack-analysis: SPU ELF. (line 29) 7197* --stats: Options. (line 1250) 7198* --strip-all: Options. (line 519) 7199* --strip-debug: Options. (line 523) 7200* --stub-group-size: PowerPC64 ELF64. (line 6) 7201* --stub-group-size=N <1>: ARM. (line 129) 7202* --stub-group-size=N: HPPA ELF32. (line 12) 7203* --subsystem: Options. (line 1928) 7204* --support-old-code: ARM. (line 6) 7205* --sysroot=DIRECTORY: Options. (line 1254) 7206* --target-help: Options. (line 961) 7207* --target1-abs: ARM. (line 32) 7208* --target1-rel: ARM. (line 32) 7209* --target2=TYPE: ARM. (line 37) 7210* --thumb-entry=ENTRY: ARM. (line 17) 7211* --trace: Options. (line 528) 7212* --trace-symbol=SYMBOL: Options. (line 597) 7213* --traditional-format: Options. (line 1259) 7214* --tsaware: Options. (line 1966) 7215* --undefined=SYMBOL: Options. (line 554) 7216* --unique[=SECTION]: Options. (line 572) 7217* --unresolved-symbols: Options. (line 1290) 7218* --use-blx: ARM. (line 74) 7219* --use-nul-prefixed-import-tables: ARM. (line 23) 7220* --verbose[=NUMBER]: Options. (line 1319) 7221* --version: Options. (line 581) 7222* --version-script=VERSION-SCRIPTFILE: Options. (line 1327) 7223* --vfp11-denorm-fix: ARM. (line 83) 7224* --warn-alternate-em: Options. (line 1439) 7225* --warn-common: Options. (line 1338) 7226* --warn-constructors: Options. (line 1406) 7227* --warn-multiple-gp: Options. (line 1411) 7228* --warn-once: Options. (line 1425) 7229* --warn-section-align: Options. (line 1429) 7230* --warn-shared-textrel: Options. (line 1436) 7231* --warn-unresolved-symbols: Options. (line 1442) 7232* --wdmdriver: Options. (line 1963) 7233* --whole-archive: Options. (line 1451) 7234* --wrap=SYMBOL: Options. (line 1465) 7235* -A ARCH: Options. (line 122) 7236* -a KEYWORD: Options. (line 105) 7237* -assert KEYWORD: Options. (line 745) 7238* -b FORMAT: Options. (line 134) 7239* -Bdynamic: Options. (line 748) 7240* -Bgroup: Options. (line 758) 7241* -Bshareable: Options. (line 1206) 7242* -Bstatic: Options. (line 765) 7243* -Bsymbolic: Options. (line 780) 7244* -Bsymbolic-functions: Options. (line 787) 7245* -c MRI-CMDFILE: Options. (line 158) 7246* -call_shared: Options. (line 748) 7247* -d: Options. (line 168) 7248* -dc: Options. (line 168) 7249* -dn: Options. (line 765) 7250* -dp: Options. (line 168) 7251* -dT SCRIPT: Options. (line 541) 7252* -dy: Options. (line 748) 7253* -E: Options. (line 221) 7254* -e ENTRY: Options. (line 187) 7255* -EB: Options. (line 248) 7256* -EL: Options. (line 251) 7257* -f NAME: Options. (line 255) 7258* -F NAME: Options. (line 276) 7259* -fini=NAME: Options. (line 300) 7260* -g: Options. (line 306) 7261* -G VALUE: Options. (line 309) 7262* -h NAME: Options. (line 317) 7263* -i: Options. (line 326) 7264* -IFILE: Options. (line 904) 7265* -init=NAME: Options. (line 329) 7266* -L DIR: Options. (line 368) 7267* -l NAMESPEC: Options. (line 335) 7268* -M: Options. (line 402) 7269* -m EMULATION: Options. (line 392) 7270* -Map=MAPFILE: Options. (line 965) 7271* -n: Options. (line 439) 7272* -N: Options. (line 445) 7273* -no-relax: Options. (line 1089) 7274* -non_shared: Options. (line 765) 7275* -nostdlib: Options. (line 1054) 7276* -O LEVEL: Options. (line 466) 7277* -o OUTPUT: Options. (line 460) 7278* -P AUDITLIB: Options. (line 177) 7279* -pie: Options. (line 1073) 7280* -q: Options. (line 476) 7281* -qmagic: Options. (line 1083) 7282* -Qy: Options. (line 1086) 7283* -r: Options. (line 489) 7284* -R FILE: Options. (line 508) 7285* -rpath-link=DIR: Options. (line 1151) 7286* -rpath=DIR: Options. (line 1129) 7287* -s: Options. (line 519) 7288* -S: Options. (line 523) 7289* -shared: Options. (line 1206) 7290* -soname=NAME: Options. (line 317) 7291* -static: Options. (line 765) 7292* -t: Options. (line 528) 7293* -T SCRIPT: Options. (line 532) 7294* -Tbss=ORG: Options. (line 1280) 7295* -Tdata=ORG: Options. (line 1280) 7296* -Ttext-segment=ORG: Options. (line 1286) 7297* -Ttext=ORG: Options. (line 1280) 7298* -u SYMBOL: Options. (line 554) 7299* -Ur: Options. (line 562) 7300* -V: Options. (line 581) 7301* -v: Options. (line 581) 7302* -X: Options. (line 591) 7303* -x: Options. (line 587) 7304* -Y PATH: Options. (line 606) 7305* -y SYMBOL: Options. (line 597) 7306* -z defs: Options. (line 976) 7307* -z KEYWORD: Options. (line 610) 7308* -z muldefs: Options. (line 984) 7309* .: Location Counter. (line 6) 7310* /DISCARD/: Output Section Discarding. 7311 (line 21) 7312* :PHDR: Output Section Phdr. 7313 (line 6) 7314* =FILLEXP: Output Section Fill. 7315 (line 6) 7316* >REGION: Output Section Region. 7317 (line 6) 7318* [COMMON]: Input Section Common. 7319 (line 29) 7320* ABSOLUTE (MRI): MRI. (line 33) 7321* absolute and relocatable symbols: Expression Section. (line 6) 7322* absolute expressions: Expression Section. (line 6) 7323* ABSOLUTE(EXP): Builtin Functions. (line 10) 7324* ADDR(SECTION): Builtin Functions. (line 17) 7325* address, section: Output Section Address. 7326 (line 6) 7327* ALIAS (MRI): MRI. (line 44) 7328* ALIGN (MRI): MRI. (line 50) 7329* align expression: Builtin Functions. (line 38) 7330* align location counter: Builtin Functions. (line 38) 7331* ALIGN(ALIGN): Builtin Functions. (line 38) 7332* ALIGN(EXP,ALIGN): Builtin Functions. (line 38) 7333* ALIGN(SECTION_ALIGN): Forced Output Alignment. 7334 (line 6) 7335* aligned common symbols: WIN32. (line 424) 7336* ALIGNOF(SECTION): Builtin Functions. (line 64) 7337* allocating memory: MEMORY. (line 6) 7338* architecture: Miscellaneous Commands. 7339 (line 72) 7340* architectures: Options. (line 122) 7341* archive files, from cmd line: Options. (line 335) 7342* archive search path in linker script: File Commands. (line 74) 7343* arithmetic: Expressions. (line 6) 7344* arithmetic operators: Operators. (line 6) 7345* ARM interworking support: ARM. (line 6) 7346* AS_NEEDED(FILES): File Commands. (line 54) 7347* ASSERT: Miscellaneous Commands. 7348 (line 9) 7349* assertion in linker script: Miscellaneous Commands. 7350 (line 9) 7351* assignment in scripts: Assignments. (line 6) 7352* AT(LMA): Output Section LMA. (line 6) 7353* AT>LMA_REGION: Output Section LMA. (line 6) 7354* automatic data imports: WIN32. (line 191) 7355* back end: BFD. (line 6) 7356* BASE (MRI): MRI. (line 54) 7357* BE8: ARM. (line 28) 7358* BFD canonical format: Canonical format. (line 11) 7359* BFD requirements: BFD. (line 16) 7360* big-endian objects: Options. (line 248) 7361* binary input format: Options. (line 134) 7362* BLOCK(EXP): Builtin Functions. (line 77) 7363* bug criteria: Bug Criteria. (line 6) 7364* bug reports: Bug Reporting. (line 6) 7365* bugs in ld: Reporting Bugs. (line 6) 7366* BYTE(EXPRESSION): Output Section Data. 7367 (line 6) 7368* C++ constructors, arranging in link: Output Section Keywords. 7369 (line 19) 7370* CHIP (MRI): MRI. (line 58) 7371* COLLECT_NO_DEMANGLE: Environment. (line 29) 7372* combining symbols, warnings on: Options. (line 1338) 7373* command files: Scripts. (line 6) 7374* command line: Options. (line 6) 7375* common allocation: Options. (line 862) 7376* common allocation in linker script: Miscellaneous Commands. 7377 (line 25) 7378* common symbol placement: Input Section Common. 7379 (line 6) 7380* COMMONPAGESIZE: Symbolic Constants. (line 13) 7381* compatibility, MRI: Options. (line 158) 7382* CONSTANT: Symbolic Constants. (line 6) 7383* constants in linker scripts: Constants. (line 6) 7384* constraints on output sections: Output Section Constraint. 7385 (line 6) 7386* CONSTRUCTORS: Output Section Keywords. 7387 (line 19) 7388* constructors: Options. (line 562) 7389* constructors, arranging in link: Output Section Keywords. 7390 (line 19) 7391* Cortex-A8 erratum workaround: i960. (line 39) 7392* crash of linker: Bug Criteria. (line 9) 7393* CREATE_OBJECT_SYMBOLS: Output Section Keywords. 7394 (line 9) 7395* creating a DEF file: WIN32. (line 158) 7396* cross reference table: Options. (line 850) 7397* cross references: Miscellaneous Commands. 7398 (line 56) 7399* current output location: Location Counter. (line 6) 7400* data: Output Section Data. 7401 (line 6) 7402* DATA_SEGMENT_ALIGN(MAXPAGESIZE, COMMONPAGESIZE): Builtin Functions. 7403 (line 82) 7404* DATA_SEGMENT_END(EXP): Builtin Functions. (line 103) 7405* DATA_SEGMENT_RELRO_END(OFFSET, EXP): Builtin Functions. (line 109) 7406* dbx: Options. (line 1264) 7407* DEF files, creating: Options. (line 1732) 7408* default emulation: Environment. (line 21) 7409* default input format: Environment. (line 9) 7410* DEFINED(SYMBOL): Builtin Functions. (line 120) 7411* deleting local symbols: Options. (line 587) 7412* demangling, default: Environment. (line 29) 7413* demangling, from command line: Options. (line 891) 7414* direct linking to a dll: WIN32. (line 239) 7415* discarding sections: Output Section Discarding. 7416 (line 6) 7417* discontinuous memory: MEMORY. (line 6) 7418* DLLs, creating: Options. (line 1634) 7419* DLLs, linking to: Options. (line 1763) 7420* dot: Location Counter. (line 6) 7421* dot inside sections: Location Counter. (line 36) 7422* dot outside sections: Location Counter. (line 66) 7423* dynamic linker, from command line: Options. (line 904) 7424* dynamic symbol table: Options. (line 221) 7425* ELF program headers: PHDRS. (line 6) 7426* emulation: Options. (line 392) 7427* emulation, default: Environment. (line 21) 7428* END (MRI): MRI. (line 62) 7429* endianness: Options. (line 248) 7430* entry point: Entry Point. (line 6) 7431* entry point, from command line: Options. (line 187) 7432* entry point, thumb: ARM. (line 17) 7433* ENTRY(SYMBOL): Entry Point. (line 6) 7434* error on valid input: Bug Criteria. (line 12) 7435* example of linker script: Simple Example. (line 6) 7436* exporting DLL symbols: WIN32. (line 19) 7437* expression evaluation order: Evaluation. (line 6) 7438* expression sections: Expression Section. (line 6) 7439* expression, absolute: Builtin Functions. (line 10) 7440* expressions: Expressions. (line 6) 7441* EXTERN: Miscellaneous Commands. 7442 (line 13) 7443* fatal signal: Bug Criteria. (line 9) 7444* file name wildcard patterns: Input Section Wildcards. 7445 (line 6) 7446* FILEHDR: PHDRS. (line 62) 7447* filename symbols: Output Section Keywords. 7448 (line 9) 7449* fill pattern, entire section: Output Section Fill. 7450 (line 6) 7451* FILL(EXPRESSION): Output Section Data. 7452 (line 39) 7453* finalization function: Options. (line 300) 7454* first input file: File Commands. (line 82) 7455* first instruction: Entry Point. (line 6) 7456* FIX_V4BX: ARM. (line 49) 7457* FIX_V4BX_INTERWORKING: ARM. (line 62) 7458* FORCE_COMMON_ALLOCATION: Miscellaneous Commands. 7459 (line 20) 7460* forcing input section alignment: Forced Input Alignment. 7461 (line 6) 7462* forcing output section alignment: Forced Output Alignment. 7463 (line 6) 7464* forcing the creation of dynamic sections: Options. (line 485) 7465* FORMAT (MRI): MRI. (line 66) 7466* functions in expressions: Builtin Functions. (line 6) 7467* garbage collection <1>: Options. (line 948) 7468* garbage collection: Input Section Keep. (line 6) 7469* generating optimized output: Options. (line 466) 7470* GNU linker: Overview. (line 6) 7471* GNUTARGET: Environment. (line 9) 7472* GROUP(FILES): File Commands. (line 47) 7473* grouping input files: File Commands. (line 47) 7474* groups of archives: Options. (line 696) 7475* H8/300 support: H8/300. (line 6) 7476* header size: Builtin Functions. (line 183) 7477* heap size: Options. (line 1674) 7478* help: Options. (line 957) 7479* holes: Location Counter. (line 12) 7480* holes, filling: Output Section Data. 7481 (line 39) 7482* HPPA multiple sub-space stubs: HPPA ELF32. (line 6) 7483* HPPA stub grouping: HPPA ELF32. (line 12) 7484* i960 support: i960. (line 6) 7485* image base: Options. (line 1681) 7486* implicit linker scripts: Implicit Linker Scripts. 7487 (line 6) 7488* import libraries: WIN32. (line 10) 7489* INCLUDE FILENAME: File Commands. (line 9) 7490* including a linker script: File Commands. (line 9) 7491* including an entire archive: Options. (line 1451) 7492* incremental link: Options. (line 326) 7493* INHIBIT_COMMON_ALLOCATION: Miscellaneous Commands. 7494 (line 25) 7495* initialization function: Options. (line 329) 7496* initialized data in ROM: Output Section LMA. (line 39) 7497* input file format in linker script: Format Commands. (line 35) 7498* input filename symbols: Output Section Keywords. 7499 (line 9) 7500* input files in linker scripts: File Commands. (line 19) 7501* input files, displaying: Options. (line 528) 7502* input format: Options. (line 134) 7503* input object files in linker scripts: File Commands. (line 19) 7504* input section alignment: Forced Input Alignment. 7505 (line 6) 7506* input section basics: Input Section Basics. 7507 (line 6) 7508* input section wildcards: Input Section Wildcards. 7509 (line 6) 7510* input sections: Input Section. (line 6) 7511* INPUT(FILES): File Commands. (line 19) 7512* INSERT: Miscellaneous Commands. 7513 (line 30) 7514* insert user script into default script: Miscellaneous Commands. 7515 (line 30) 7516* integer notation: Constants. (line 6) 7517* integer suffixes: Constants. (line 15) 7518* internal object-file format: Canonical format. (line 11) 7519* invalid input: Bug Criteria. (line 14) 7520* K and M integer suffixes: Constants. (line 15) 7521* KEEP: Input Section Keep. (line 6) 7522* l =: MEMORY. (line 74) 7523* lazy evaluation: Evaluation. (line 6) 7524* ld bugs, reporting: Bug Reporting. (line 6) 7525* LD_FEATURE(STRING): Miscellaneous Commands. 7526 (line 78) 7527* LDEMULATION: Environment. (line 21) 7528* len =: MEMORY. (line 74) 7529* LENGTH =: MEMORY. (line 74) 7530* LENGTH(MEMORY): Builtin Functions. (line 137) 7531* library search path in linker script: File Commands. (line 74) 7532* link map: Options. (line 402) 7533* link-time runtime library search path: Options. (line 1151) 7534* linker crash: Bug Criteria. (line 9) 7535* linker script concepts: Basic Script Concepts. 7536 (line 6) 7537* linker script example: Simple Example. (line 6) 7538* linker script file commands: File Commands. (line 6) 7539* linker script format: Script Format. (line 6) 7540* linker script input object files: File Commands. (line 19) 7541* linker script simple commands: Simple Commands. (line 6) 7542* linker scripts: Scripts. (line 6) 7543* LIST (MRI): MRI. (line 77) 7544* little-endian objects: Options. (line 251) 7545* LOAD (MRI): MRI. (line 84) 7546* load address: Output Section LMA. (line 6) 7547* LOADADDR(SECTION): Builtin Functions. (line 140) 7548* loading, preventing: Output Section Type. 7549 (line 22) 7550* local symbols, deleting: Options. (line 591) 7551* location counter: Location Counter. (line 6) 7552* LONG(EXPRESSION): Output Section Data. 7553 (line 6) 7554* M and K integer suffixes: Constants. (line 15) 7555* M68HC11 and 68HC12 support: M68HC11/68HC12. (line 6) 7556* machine architecture: Miscellaneous Commands. 7557 (line 72) 7558* machine dependencies: Machine Dependent. (line 6) 7559* mapping input sections to output sections: Input Section. (line 6) 7560* MAX: Builtin Functions. (line 143) 7561* MAXPAGESIZE: Symbolic Constants. (line 10) 7562* MEMORY: MEMORY. (line 6) 7563* memory region attributes: MEMORY. (line 34) 7564* memory regions: MEMORY. (line 6) 7565* memory regions and sections: Output Section Region. 7566 (line 6) 7567* memory usage: Options. (line 969) 7568* MIN: Builtin Functions. (line 146) 7569* Motorola 68K GOT generation: M68K. (line 6) 7570* MRI compatibility: MRI. (line 6) 7571* MSP430 extra sections: MSP430. (line 11) 7572* NAME (MRI): MRI. (line 90) 7573* name, section: Output Section Name. 7574 (line 6) 7575* names: Symbols. (line 6) 7576* naming the output file: Options. (line 460) 7577* NEXT(EXP): Builtin Functions. (line 150) 7578* NMAGIC: Options. (line 439) 7579* NO_ENUM_SIZE_WARNING: ARM. (line 111) 7580* NO_WCHAR_SIZE_WARNING: ARM. (line 118) 7581* NOCROSSREFS(SECTIONS): Miscellaneous Commands. 7582 (line 56) 7583* NOLOAD: Output Section Type. 7584 (line 22) 7585* not enough room for program headers: Builtin Functions. (line 188) 7586* o =: MEMORY. (line 69) 7587* objdump -i: BFD. (line 6) 7588* object file management: BFD. (line 6) 7589* object files: Options. (line 29) 7590* object formats available: BFD. (line 6) 7591* object size: Options. (line 309) 7592* OMAGIC: Options. (line 454) 7593* ONLY_IF_RO: Output Section Constraint. 7594 (line 6) 7595* ONLY_IF_RW: Output Section Constraint. 7596 (line 6) 7597* opening object files: BFD outline. (line 6) 7598* operators for arithmetic: Operators. (line 6) 7599* options: Options. (line 6) 7600* ORDER (MRI): MRI. (line 95) 7601* org =: MEMORY. (line 69) 7602* ORIGIN =: MEMORY. (line 69) 7603* ORIGIN(MEMORY): Builtin Functions. (line 156) 7604* orphan: Orphan Sections. (line 6) 7605* output file after errors: Options. (line 1048) 7606* output file format in linker script: Format Commands. (line 10) 7607* output file name in linker script: File Commands. (line 64) 7608* output section alignment: Forced Output Alignment. 7609 (line 6) 7610* output section attributes: Output Section Attributes. 7611 (line 6) 7612* output section data: Output Section Data. 7613 (line 6) 7614* OUTPUT(FILENAME): File Commands. (line 64) 7615* OUTPUT_ARCH(BFDARCH): Miscellaneous Commands. 7616 (line 72) 7617* OUTPUT_FORMAT(BFDNAME): Format Commands. (line 10) 7618* OVERLAY: Overlay Description. 7619 (line 6) 7620* overlays: Overlay Description. 7621 (line 6) 7622* partial link: Options. (line 489) 7623* PE import table prefixing: ARM. (line 23) 7624* PHDRS: PHDRS. (line 62) 7625* PIC_VENEER: ARM. (line 124) 7626* position independent executables: Options. (line 1075) 7627* PowerPC ELF32 options: PowerPC ELF32. (line 16) 7628* PowerPC GOT: PowerPC ELF32. (line 33) 7629* PowerPC long branches: PowerPC ELF32. (line 6) 7630* PowerPC PLT: PowerPC ELF32. (line 16) 7631* PowerPC stub symbols: PowerPC ELF32. (line 47) 7632* PowerPC TLS optimization: PowerPC ELF32. (line 51) 7633* PowerPC64 dot symbols: PowerPC64 ELF64. (line 33) 7634* PowerPC64 ELF64 options: PowerPC64 ELF64. (line 6) 7635* PowerPC64 multi-TOC: PowerPC64 ELF64. (line 74) 7636* PowerPC64 OPD optimization: PowerPC64 ELF64. (line 48) 7637* PowerPC64 OPD spacing: PowerPC64 ELF64. (line 54) 7638* PowerPC64 stub grouping: PowerPC64 ELF64. (line 6) 7639* PowerPC64 stub symbols: PowerPC64 ELF64. (line 29) 7640* PowerPC64 TLS optimization: PowerPC64 ELF64. (line 43) 7641* PowerPC64 TOC optimization: PowerPC64 ELF64. (line 60) 7642* precedence in expressions: Operators. (line 6) 7643* prevent unnecessary loading: Output Section Type. 7644 (line 22) 7645* program headers: PHDRS. (line 6) 7646* program headers and sections: Output Section Phdr. 7647 (line 6) 7648* program headers, not enough room: Builtin Functions. (line 188) 7649* program segments: PHDRS. (line 6) 7650* PROVIDE: PROVIDE. (line 6) 7651* PROVIDE_HIDDEN: PROVIDE_HIDDEN. (line 6) 7652* PUBLIC (MRI): MRI. (line 103) 7653* QUAD(EXPRESSION): Output Section Data. 7654 (line 6) 7655* quoted symbol names: Symbols. (line 6) 7656* read-only text: Options. (line 439) 7657* read/write from cmd line: Options. (line 445) 7658* region alias: REGION_ALIAS. (line 6) 7659* region names: REGION_ALIAS. (line 6) 7660* REGION_ALIAS(ALIAS, REGION): REGION_ALIAS. (line 6) 7661* regions of memory: MEMORY. (line 6) 7662* relative expressions: Expression Section. (line 6) 7663* relaxing addressing modes: Options. (line 1089) 7664* relaxing on H8/300: H8/300. (line 9) 7665* relaxing on i960: i960. (line 31) 7666* relaxing on M68HC11: M68HC11/68HC12. (line 12) 7667* relaxing on Xtensa: Xtensa. (line 27) 7668* relocatable and absolute symbols: Expression Section. (line 6) 7669* relocatable output: Options. (line 489) 7670* removing sections: Output Section Discarding. 7671 (line 6) 7672* reporting bugs in ld: Reporting Bugs. (line 6) 7673* requirements for BFD: BFD. (line 16) 7674* retain relocations in final executable: Options. (line 476) 7675* retaining specified symbols: Options. (line 1115) 7676* ROM initialized data: Output Section LMA. (line 39) 7677* round up expression: Builtin Functions. (line 38) 7678* round up location counter: Builtin Functions. (line 38) 7679* runtime library name: Options. (line 317) 7680* runtime library search path: Options. (line 1129) 7681* runtime pseudo-relocation: WIN32. (line 217) 7682* scaled integers: Constants. (line 15) 7683* scommon section: Input Section Common. 7684 (line 20) 7685* script files: Options. (line 532) 7686* scripts: Scripts. (line 6) 7687* search directory, from cmd line: Options. (line 368) 7688* search path in linker script: File Commands. (line 74) 7689* SEARCH_DIR(PATH): File Commands. (line 74) 7690* SECT (MRI): MRI. (line 109) 7691* section address: Output Section Address. 7692 (line 6) 7693* section address in expression: Builtin Functions. (line 17) 7694* section alignment: Builtin Functions. (line 64) 7695* section alignment, warnings on: Options. (line 1429) 7696* section data: Output Section Data. 7697 (line 6) 7698* section fill pattern: Output Section Fill. 7699 (line 6) 7700* section load address: Output Section LMA. (line 6) 7701* section load address in expression: Builtin Functions. (line 140) 7702* section name: Output Section Name. 7703 (line 6) 7704* section name wildcard patterns: Input Section Wildcards. 7705 (line 6) 7706* section size: Builtin Functions. (line 167) 7707* section, assigning to memory region: Output Section Region. 7708 (line 6) 7709* section, assigning to program header: Output Section Phdr. 7710 (line 6) 7711* SECTIONS: SECTIONS. (line 6) 7712* sections, discarding: Output Section Discarding. 7713 (line 6) 7714* segment origins, cmd line: Options. (line 1280) 7715* SEGMENT_START(SEGMENT, DEFAULT): Builtin Functions. (line 159) 7716* segments, ELF: PHDRS. (line 6) 7717* shared libraries: Options. (line 1208) 7718* SHORT(EXPRESSION): Output Section Data. 7719 (line 6) 7720* SIZEOF(SECTION): Builtin Functions. (line 167) 7721* SIZEOF_HEADERS: Builtin Functions. (line 183) 7722* small common symbols: Input Section Common. 7723 (line 20) 7724* SORT: Input Section Wildcards. 7725 (line 58) 7726* SORT_BY_ALIGNMENT: Input Section Wildcards. 7727 (line 54) 7728* SORT_BY_NAME: Input Section Wildcards. 7729 (line 46) 7730* SPU: SPU ELF. (line 29) 7731* SPU ELF options: SPU ELF. (line 6) 7732* SPU extra overlay stubs: SPU ELF. (line 19) 7733* SPU local store size: SPU ELF. (line 24) 7734* SPU overlay stub symbols: SPU ELF. (line 15) 7735* SPU overlays: SPU ELF. (line 9) 7736* SPU plugins: SPU ELF. (line 6) 7737* SQUAD(EXPRESSION): Output Section Data. 7738 (line 6) 7739* stack size: Options. (line 1921) 7740* standard Unix system: Options. (line 7) 7741* start of execution: Entry Point. (line 6) 7742* STARTUP(FILENAME): File Commands. (line 82) 7743* strip all symbols: Options. (line 519) 7744* strip debugger symbols: Options. (line 523) 7745* stripping all but some symbols: Options. (line 1115) 7746* STUB_GROUP_SIZE: ARM. (line 129) 7747* SUBALIGN(SUBSECTION_ALIGN): Forced Input Alignment. 7748 (line 6) 7749* suffixes for integers: Constants. (line 15) 7750* symbol defaults: Builtin Functions. (line 120) 7751* symbol definition, scripts: Assignments. (line 6) 7752* symbol names: Symbols. (line 6) 7753* symbol tracing: Options. (line 597) 7754* symbol versions: VERSION. (line 6) 7755* symbol-only input: Options. (line 508) 7756* symbolic constants: Symbolic Constants. (line 6) 7757* symbols, from command line: Options. (line 878) 7758* symbols, relocatable and absolute: Expression Section. (line 6) 7759* symbols, retaining selectively: Options. (line 1115) 7760* synthesizing linker: Options. (line 1089) 7761* synthesizing on H8/300: H8/300. (line 14) 7762* TARGET(BFDNAME): Format Commands. (line 35) 7763* TARGET1: ARM. (line 32) 7764* TARGET2: ARM. (line 37) 7765* text segment origin, cmd line: Options. (line 1287) 7766* thumb entry point: ARM. (line 17) 7767* TI COFF versions: TI COFF. (line 6) 7768* traditional format: Options. (line 1259) 7769* trampoline generation on M68HC11: M68HC11/68HC12. (line 31) 7770* trampoline generation on M68HC12: M68HC11/68HC12. (line 31) 7771* unallocated address, next: Builtin Functions. (line 150) 7772* undefined symbol: Options. (line 554) 7773* undefined symbol in linker script: Miscellaneous Commands. 7774 (line 13) 7775* undefined symbols, warnings on: Options. (line 1425) 7776* uninitialized data placement: Input Section Common. 7777 (line 6) 7778* unspecified memory: Output Section Data. 7779 (line 39) 7780* usage: Options. (line 957) 7781* USE_BLX: ARM. (line 74) 7782* using a DEF file: WIN32. (line 57) 7783* using auto-export functionality: WIN32. (line 22) 7784* Using decorations: WIN32. (line 162) 7785* variables, defining: Assignments. (line 6) 7786* verbose[=NUMBER]: Options. (line 1319) 7787* version: Options. (line 581) 7788* version script: VERSION. (line 6) 7789* version script, symbol versions: Options. (line 1327) 7790* VERSION {script text}: VERSION. (line 6) 7791* versions of symbols: VERSION. (line 6) 7792* VFP11_DENORM_FIX: ARM. (line 83) 7793* warnings, on combining symbols: Options. (line 1338) 7794* warnings, on section alignment: Options. (line 1429) 7795* warnings, on undefined symbols: Options. (line 1425) 7796* weak externals: WIN32. (line 407) 7797* what is this?: Overview. (line 6) 7798* wildcard file name patterns: Input Section Wildcards. 7799 (line 6) 7800* Xtensa options: Xtensa. (line 56) 7801* Xtensa processors: Xtensa. (line 6) 7802 7803 7804 7805Tag Table: 7806Node: Top815 7807Node: Overview1600 7808Node: Invocation2714 7809Node: Options3122 7810Node: Environment93440 7811Node: Scripts95200 7812Node: Basic Script Concepts96934 7813Node: Script Format99641 7814Node: Simple Example100504 7815Node: Simple Commands103600 7816Node: Entry Point104106 7817Node: File Commands105039 7818Node: Format Commands109040 7819Node: REGION_ALIAS110996 7820Node: Miscellaneous Commands115828 7821Node: Assignments119436 7822Node: Simple Assignments119927 7823Node: PROVIDE121663 7824Node: PROVIDE_HIDDEN122868 7825Node: Source Code Reference123112 7826Node: SECTIONS126692 7827Node: Output Section Description128583 7828Node: Output Section Name129670 7829Node: Output Section Address130546 7830Node: Input Section132781 7831Node: Input Section Basics133582 7832Node: Input Section Wildcards136800 7833Node: Input Section Common141533 7834Node: Input Section Keep143015 7835Node: Input Section Example143505 7836Node: Output Section Data144473 7837Node: Output Section Keywords147250 7838Node: Output Section Discarding150819 7839Node: Output Section Attributes152000 7840Node: Output Section Type153101 7841Node: Output Section LMA154172 7842Node: Forced Output Alignment157243 7843Node: Forced Input Alignment157511 7844Node: Output Section Constraint157900 7845Node: Output Section Region158328 7846Node: Output Section Phdr158761 7847Node: Output Section Fill159425 7848Node: Overlay Description160567 7849Node: MEMORY164870 7850Node: PHDRS169205 7851Node: VERSION174459 7852Node: Expressions182552 7853Node: Constants183481 7854Node: Symbolic Constants184356 7855Node: Symbols184907 7856Node: Orphan Sections185654 7857Node: Location Counter186818 7858Node: Operators191254 7859Node: Evaluation192176 7860Node: Expression Section193540 7861Node: Builtin Functions197197 7862Node: Implicit Linker Scripts205158 7863Node: Machine Dependent205933 7864Node: H8/300206949 7865Node: i960208574 7866Node: M68HC11/68HC12210778 7867Node: ARM212232 7868Node: HPPA ELF32219744 7869Node: M68K221367 7870Node: MMIX222276 7871Node: MSP430223441 7872Node: PowerPC ELF32224490 7873Node: PowerPC64 ELF64227326 7874Node: SPU ELF231742 7875Node: TI COFF234374 7876Node: WIN32234900 7877Node: Xtensa255025 7878Node: BFD257990 7879Node: BFD outline259445 7880Node: BFD information loss260731 7881Node: Canonical format263248 7882Node: Reporting Bugs267605 7883Node: Bug Criteria268299 7884Node: Bug Reporting268998 7885Node: MRI276037 7886Node: GNU Free Documentation License280680 7887Node: LD Index305836 7888 7889End Tag Table 7890