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1<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd"> 2<html> 3<!-- Copyright (C) 1988-2017 Free Software Foundation, Inc. 4 5Permission is granted to copy, distribute and/or modify this document 6under the terms of the GNU Free Documentation License, Version 1.3 or 7any later version published by the Free Software Foundation; with no 8Invariant Sections, the Front-Cover texts being (a) (see below), and 9with the Back-Cover Texts being (b) (see below). A copy of the 10license is included in the section entitled "GNU 11Free Documentation License". 12 13(a) The FSF's Front-Cover Text is: 14 15A GNU Manual 16 17(b) The FSF's Back-Cover Text is: 18 19You have freedom to copy and modify this GNU Manual, like GNU 20 software. Copies published by the Free Software Foundation raise 21 funds for GNU development. --> 22<!-- Created by GNU Texinfo 6.4, http://www.gnu.org/software/texinfo/ --> 23<head> 24<title>Installing GCC</title> 25 26<meta name="description" content="Installing GCC"> 27<meta name="keywords" content="Installing GCC"> 28<meta name="resource-type" content="document"> 29<meta name="distribution" content="global"> 30<meta name="Generator" content="makeinfo"> 31<meta http-equiv="Content-Type" content="text/html; charset=utf-8"> 32<style type="text/css"> 33<!-- 34a.summary-letter {text-decoration: none} 35blockquote.indentedblock {margin-right: 0em} 36blockquote.smallindentedblock {margin-right: 0em; font-size: smaller} 37blockquote.smallquotation {font-size: smaller} 38div.display {margin-left: 3.2em} 39div.example {margin-left: 3.2em} 40div.lisp {margin-left: 3.2em} 41div.smalldisplay {margin-left: 3.2em} 42div.smallexample {margin-left: 3.2em} 43div.smalllisp {margin-left: 3.2em} 44kbd {font-style: oblique} 45pre.display {font-family: inherit} 46pre.format {font-family: inherit} 47pre.menu-comment {font-family: serif} 48pre.menu-preformatted {font-family: serif} 49pre.smalldisplay {font-family: inherit; font-size: smaller} 50pre.smallexample {font-size: smaller} 51pre.smallformat {font-family: inherit; font-size: smaller} 52pre.smalllisp {font-size: smaller} 53span.nolinebreak {white-space: nowrap} 54span.roman {font-family: initial; font-weight: normal} 55span.sansserif {font-family: sans-serif; font-weight: normal} 56ul.no-bullet {list-style: none} 57--> 58</style> 59 60 61</head> 62 63<body lang="en"> 64<h1 class="settitle" align="center">Installing GCC</h1> 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85<a name="index-Installing-GCC_003a-Building"></a> 86 87<p>Now that GCC is configured, you are ready to build the compiler and 88runtime libraries. 89</p> 90<p>Some commands executed when making the compiler may fail (return a 91nonzero status) and be ignored by <code>make</code>. These failures, which 92are often due to files that were not found, are expected, and can safely 93be ignored. 94</p> 95<p>It is normal to have compiler warnings when compiling certain files. 96Unless you are a GCC developer, you can generally ignore these warnings 97unless they cause compilation to fail. Developers should attempt to fix 98any warnings encountered, however they can temporarily continue past 99warnings-as-errors by specifying the configure flag 100<samp>--disable-werror</samp>. 101</p> 102<p>On certain old systems, defining certain environment variables such as 103<code>CC</code> can interfere with the functioning of <code>make</code>. 104</p> 105<p>If you encounter seemingly strange errors when trying to build the 106compiler in a directory other than the source directory, it could be 107because you have previously configured the compiler in the source 108directory. Make sure you have done all the necessary preparations. 109</p> 110<p>If you build GCC on a BSD system using a directory stored in an old System 111V file system, problems may occur in running <code>fixincludes</code> if the 112System V file system doesn’t support symbolic links. These problems 113result in a failure to fix the declaration of <code>size_t</code> in 114<samp>sys/types.h</samp>. If you find that <code>size_t</code> is a signed type and 115that type mismatches occur, this could be the cause. 116</p> 117<p>The solution is not to use such a directory for building GCC. 118</p> 119<p>Similarly, when building from SVN or snapshots, or if you modify 120<samp>*.l</samp> files, you need the Flex lexical analyzer generator 121installed. If you do not modify <samp>*.l</samp> files, releases contain 122the Flex-generated files and you do not need Flex installed to build 123them. There is still one Flex-based lexical analyzer (part of the 124build machinery, not of GCC itself) that is used even if you only 125build the C front end. 126</p> 127<p>When building from SVN or snapshots, or if you modify Texinfo 128documentation, you need version 4.7 or later of Texinfo installed if you 129want Info documentation to be regenerated. Releases contain Info 130documentation pre-built for the unmodified documentation in the release. 131</p> 132<a name="Building-a-native-compiler"></a> 133<h3 class="section">Building a native compiler</h3> 134 135<p>For a native build, the default configuration is to perform 136a 3-stage bootstrap of the compiler when ‘<samp>make</samp>’ is invoked. 137This will build the entire GCC system and ensure that it compiles 138itself correctly. It can be disabled with the <samp>--disable-bootstrap</samp> 139parameter to ‘<samp>configure</samp>’, but bootstrapping is suggested because 140the compiler will be tested more completely and could also have 141better performance. 142</p> 143<p>The bootstrapping process will complete the following steps: 144</p> 145<ul> 146<li> Build tools necessary to build the compiler. 147 148</li><li> Perform a 3-stage bootstrap of the compiler. This includes building 149three times the target tools for use by the compiler such as binutils 150(bfd, binutils, gas, gprof, ld, and opcodes) if they have been 151individually linked or moved into the top level GCC source tree before 152configuring. 153 154</li><li> Perform a comparison test of the stage2 and stage3 compilers. 155 156</li><li> Build runtime libraries using the stage3 compiler from the previous step. 157 158</li></ul> 159 160<p>If you are short on disk space you might consider ‘<samp>make 161bootstrap-lean</samp>’ instead. The sequence of compilation is the 162same described above, but object files from the stage1 and 163stage2 of the 3-stage bootstrap of the compiler are deleted as 164soon as they are no longer needed. 165</p> 166<p>If you wish to use non-default GCC flags when compiling the stage2 167and stage3 compilers, set <code>BOOT_CFLAGS</code> on the command line when 168doing ‘<samp>make</samp>’. For example, if you want to save additional space 169during the bootstrap and in the final installation as well, you can 170build the compiler binaries without debugging information as in the 171following example. This will save roughly 40% of disk space both for 172the bootstrap and the final installation. (Libraries will still contain 173debugging information.) 174</p> 175<div class="smallexample"> 176<pre class="smallexample">make BOOT_CFLAGS='-O' bootstrap 177</pre></div> 178 179<p>You can place non-default optimization flags into <code>BOOT_CFLAGS</code>; they 180are less well tested here than the default of ‘<samp>-g -O2</samp>’, but should 181still work. In a few cases, you may find that you need to specify special 182flags such as <samp>-msoft-float</samp> here to complete the bootstrap; or, 183if the native compiler miscompiles the stage1 compiler, you may need 184to work around this, by choosing <code>BOOT_CFLAGS</code> to avoid the parts 185of the stage1 compiler that were miscompiled, or by using ‘<samp>make 186bootstrap4</samp>’ to increase the number of stages of bootstrap. 187</p> 188<p><code>BOOT_CFLAGS</code> does not apply to bootstrapped target libraries. 189Since these are always compiled with the compiler currently being 190bootstrapped, you can use <code>CFLAGS_FOR_TARGET</code> to modify their 191compilation flags, as for non-bootstrapped target libraries. 192Again, if the native compiler miscompiles the stage1 compiler, you may 193need to work around this by avoiding non-working parts of the stage1 194compiler. Use <code>STAGE1_TFLAGS</code> to this end. 195</p> 196<p>If you used the flag <samp>--enable-languages=…</samp> to restrict 197the compilers to be built, only those you’ve actually enabled will be 198built. This will of course only build those runtime libraries, for 199which the particular compiler has been built. Please note, 200that re-defining <code>LANGUAGES</code> when calling ‘<samp>make</samp>’ 201<strong>does not</strong> work anymore! 202</p> 203<p>If the comparison of stage2 and stage3 fails, this normally indicates 204that the stage2 compiler has compiled GCC incorrectly, and is therefore 205a potentially serious bug which you should investigate and report. (On 206a few systems, meaningful comparison of object files is impossible; they 207always appear “different”. If you encounter this problem, you will 208need to disable comparison in the <samp>Makefile</samp>.) 209</p> 210<p>If you do not want to bootstrap your compiler, you can configure with 211<samp>--disable-bootstrap</samp>. In particular cases, you may want to 212bootstrap your compiler even if the target system is not the same as 213the one you are building on: for example, you could build a 214<code>powerpc-unknown-linux-gnu</code> toolchain on a 215<code>powerpc64-unknown-linux-gnu</code> host. In this case, pass 216<samp>--enable-bootstrap</samp> to the configure script. 217</p> 218<p><code>BUILD_CONFIG</code> can be used to bring in additional customization 219to the build. It can be set to a whitespace-separated list of names. 220For each such <code>NAME</code>, top-level <samp>config/<code>NAME</code>.mk</samp> will 221be included by the top-level <samp>Makefile</samp>, bringing in any settings 222it contains. The default <code>BUILD_CONFIG</code> can be set using the 223configure option <samp>--with-build-config=<code>NAME</code>...</samp>. Some 224examples of supported build configurations are: 225</p> 226<dl compact="compact"> 227<dt>‘<samp>bootstrap-O1</samp>’</dt> 228<dd><p>Removes any <samp>-O</samp>-started option from <code>BOOT_CFLAGS</code>, and adds 229<samp>-O1</samp> to it. ‘<samp>BUILD_CONFIG=bootstrap-O1</samp>’ is equivalent to 230‘<samp>BOOT_CFLAGS='-g -O1'</samp>’. 231</p> 232</dd> 233<dt>‘<samp>bootstrap-O3</samp>’</dt> 234<dd><p>Analogous to <code>bootstrap-O1</code>. 235</p> 236</dd> 237<dt>‘<samp>bootstrap-lto</samp>’</dt> 238<dd><p>Enables Link-Time Optimization for host tools during bootstrapping. 239‘<samp>BUILD_CONFIG=bootstrap-lto</samp>’ is equivalent to adding 240<samp>-flto</samp> to ‘<samp>BOOT_CFLAGS</samp>’. This option assumes that the host 241supports the linker plugin (e.g. GNU ld version 2.21 or later or GNU gold 242version 2.21 or later). 243</p> 244</dd> 245<dt>‘<samp>bootstrap-lto-noplugin</samp>’</dt> 246<dd><p>This option is similar to <code>bootstrap-lto</code>, but is intended for 247hosts that do not support the linker plugin. Without the linker plugin 248static libraries are not compiled with link-time optimizations. Since 249the GCC middle end and back end are in <samp>libbackend.a</samp> this means 250that only the front end is actually LTO optimized. 251</p> 252</dd> 253<dt>‘<samp>bootstrap-debug</samp>’</dt> 254<dd><p>Verifies that the compiler generates the same executable code, whether 255or not it is asked to emit debug information. To this end, this 256option builds stage2 host programs without debug information, and uses 257<samp>contrib/compare-debug</samp> to compare them with the stripped stage3 258object files. If <code>BOOT_CFLAGS</code> is overridden so as to not enable 259debug information, stage2 will have it, and stage3 won’t. This option 260is enabled by default when GCC bootstrapping is enabled, if 261<code>strip</code> can turn object files compiled with and without debug 262info into identical object files. In addition to better test 263coverage, this option makes default bootstraps faster and leaner. 264</p> 265</dd> 266<dt>‘<samp>bootstrap-debug-big</samp>’</dt> 267<dd><p>Rather than comparing stripped object files, as in 268<code>bootstrap-debug</code>, this option saves internal compiler dumps 269during stage2 and stage3 and compares them as well, which helps catch 270additional potential problems, but at a great cost in terms of disk 271space. It can be specified in addition to ‘<samp>bootstrap-debug</samp>’. 272</p> 273</dd> 274<dt>‘<samp>bootstrap-debug-lean</samp>’</dt> 275<dd><p>This option saves disk space compared with <code>bootstrap-debug-big</code>, 276but at the expense of some recompilation. Instead of saving the dumps 277of stage2 and stage3 until the final compare, it uses 278<samp>-fcompare-debug</samp> to generate, compare and remove the dumps 279during stage3, repeating the compilation that already took place in 280stage2, whose dumps were not saved. 281</p> 282</dd> 283<dt>‘<samp>bootstrap-debug-lib</samp>’</dt> 284<dd><p>This option tests executable code invariance over debug information 285generation on target libraries, just like <code>bootstrap-debug-lean</code> 286tests it on host programs. It builds stage3 libraries with 287<samp>-fcompare-debug</samp>, and it can be used along with any of the 288<code>bootstrap-debug</code> options above. 289</p> 290<p>There aren’t <code>-lean</code> or <code>-big</code> counterparts to this option 291because most libraries are only build in stage3, so bootstrap compares 292would not get significant coverage. Moreover, the few libraries built 293in stage2 are used in stage3 host programs, so we wouldn’t want to 294compile stage2 libraries with different options for comparison purposes. 295</p> 296</dd> 297<dt>‘<samp>bootstrap-debug-ckovw</samp>’</dt> 298<dd><p>Arranges for error messages to be issued if the compiler built on any 299stage is run without the option <samp>-fcompare-debug</samp>. This is 300useful to verify the full <samp>-fcompare-debug</samp> testing coverage. It 301must be used along with <code>bootstrap-debug-lean</code> and 302<code>bootstrap-debug-lib</code>. 303</p> 304</dd> 305<dt>‘<samp>bootstrap-time</samp>’</dt> 306<dd><p>Arranges for the run time of each program started by the GCC driver, 307built in any stage, to be logged to <samp>time.log</samp>, in the top level of 308the build tree. 309</p> 310</dd> 311</dl> 312 313<a name="Building-a-cross-compiler"></a> 314<h3 class="section">Building a cross compiler</h3> 315 316<p>When building a cross compiler, it is not generally possible to do a 3173-stage bootstrap of the compiler. This makes for an interesting problem 318as parts of GCC can only be built with GCC. 319</p> 320<p>To build a cross compiler, we recommend first building and installing a 321native compiler. You can then use the native GCC compiler to build the 322cross compiler. The installed native compiler needs to be GCC version 3232.95 or later. 324</p> 325<p>If the cross compiler is to be built with support for the Java 326programming language and the ability to compile .java source files is 327desired, the installed native compiler used to build the cross 328compiler needs to be the same GCC version as the cross compiler. In 329addition the cross compiler needs to be configured with 330<samp>--with-ecj-jar=…</samp>. 331</p> 332<p>Assuming you have already installed a native copy of GCC and configured 333your cross compiler, issue the command <code>make</code>, which performs the 334following steps: 335</p> 336<ul> 337<li> Build host tools necessary to build the compiler. 338 339</li><li> Build target tools for use by the compiler such as binutils (bfd, 340binutils, gas, gprof, ld, and opcodes) 341if they have been individually linked or moved into the top level GCC source 342tree before configuring. 343 344</li><li> Build the compiler (single stage only). 345 346</li><li> Build runtime libraries using the compiler from the previous step. 347</li></ul> 348 349<p>Note that if an error occurs in any step the make process will exit. 350</p> 351<p>If you are not building GNU binutils in the same source tree as GCC, 352you will need a cross-assembler and cross-linker installed before 353configuring GCC. Put them in the directory 354<samp><var>prefix</var>/<var>target</var>/bin</samp>. Here is a table of the tools 355you should put in this directory: 356</p> 357<dl compact="compact"> 358<dt><samp>as</samp></dt> 359<dd><p>This should be the cross-assembler. 360</p> 361</dd> 362<dt><samp>ld</samp></dt> 363<dd><p>This should be the cross-linker. 364</p> 365</dd> 366<dt><samp>ar</samp></dt> 367<dd><p>This should be the cross-archiver: a program which can manipulate 368archive files (linker libraries) in the target machine’s format. 369</p> 370</dd> 371<dt><samp>ranlib</samp></dt> 372<dd><p>This should be a program to construct a symbol table in an archive file. 373</p></dd> 374</dl> 375 376<p>The installation of GCC will find these programs in that directory, 377and copy or link them to the proper place to for the cross-compiler to 378find them when run later. 379</p> 380<p>The easiest way to provide these files is to build the Binutils package. 381Configure it with the same <samp>--host</samp> and <samp>--target</samp> 382options that you use for configuring GCC, then build and install 383them. They install their executables automatically into the proper 384directory. Alas, they do not support all the targets that GCC 385supports. 386</p> 387<p>If you are not building a C library in the same source tree as GCC, 388you should also provide the target libraries and headers before 389configuring GCC, specifying the directories with 390<samp>--with-sysroot</samp> or <samp>--with-headers</samp> and 391<samp>--with-libs</samp>. Many targets also require “start files” such 392as <samp>crt0.o</samp> and 393<samp>crtn.o</samp> which are linked into each executable. There may be several 394alternatives for <samp>crt0.o</samp>, for use with profiling or other 395compilation options. Check your target’s definition of 396<code>STARTFILE_SPEC</code> to find out what start files it uses. 397</p> 398<a name="Building-in-parallel"></a> 399<h3 class="section">Building in parallel</h3> 400 401<p>GNU Make 3.80 and above, which is necessary to build GCC, support 402building in parallel. To activate this, you can use ‘<samp>make -j 2</samp>’ 403instead of ‘<samp>make</samp>’. You can also specify a bigger number, and 404in most cases using a value greater than the number of processors in 405your machine will result in fewer and shorter I/O latency hits, thus 406improving overall throughput; this is especially true for slow drives 407and network filesystems. 408</p> 409<a name="Building-the-Ada-compiler"></a> 410<h3 class="section">Building the Ada compiler</h3> 411 412<p>In order to build GNAT, the Ada compiler, you need a working GNAT 413compiler (GCC version 4.0 or later). 414This includes GNAT tools such as <code>gnatmake</code> and 415<code>gnatlink</code>, since the Ada front end is written in Ada and 416uses some GNAT-specific extensions. 417</p> 418<p>In order to build a cross compiler, it is suggested to install 419the new compiler as native first, and then use it to build the cross 420compiler. 421</p> 422<p><code>configure</code> does not test whether the GNAT installation works 423and has a sufficiently recent version; if too old a GNAT version is 424installed, the build will fail unless <samp>--enable-languages</samp> is 425used to disable building the Ada front end. 426</p> 427<p><code>ADA_INCLUDE_PATH</code> and <code>ADA_OBJECT_PATH</code> environment variables 428must not be set when building the Ada compiler, the Ada tools, or the 429Ada runtime libraries. You can check that your build environment is clean 430by verifying that ‘<samp>gnatls -v</samp>’ lists only one explicit path in each 431section. 432</p> 433<a name="Building-with-profile-feedback"></a> 434<h3 class="section">Building with profile feedback</h3> 435 436<p>It is possible to use profile feedback to optimize the compiler itself. This 437should result in a faster compiler binary. Experiments done on x86 using gcc 4383.3 showed approximately 7 percent speedup on compiling C programs. To 439bootstrap the compiler with profile feedback, use <code>make profiledbootstrap</code>. 440</p> 441<p>When ‘<samp>make profiledbootstrap</samp>’ is run, it will first build a <code>stage1</code> 442compiler. This compiler is used to build a <code>stageprofile</code> compiler 443instrumented to collect execution counts of instruction and branch 444probabilities. Then runtime libraries are compiled with profile collected. 445Finally a <code>stagefeedback</code> compiler is built using the information collected. 446</p> 447<p>Unlike standard bootstrap, several additional restrictions apply. The 448compiler used to build <code>stage1</code> needs to support a 64-bit integral type. 449It is recommended to only use GCC for this. 450</p> 451<hr /> 452<p> 453<p><a href="./index.html">Return to the GCC Installation page</a> 454</p> 455 456 457 458 459 460 461 462<hr> 463 464 465 466</body> 467</html> 468