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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) 1988-2019 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 6.5, http://www.gnu.org/software/texinfo/ --> 23<head> 24<meta http-equiv="Content-Type" content="text/html; charset=utf-8"> 25<title>Installing GCC</title> 26 27<meta name="description" content="Installing GCC"> 28<meta name="keywords" content="Installing GCC"> 29<meta name="resource-type" content="document"> 30<meta name="distribution" content="global"> 31<meta name="Generator" content="makeinfo"> 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 the source repository 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 the source repository 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-lto-lean</samp>’</dt> 254<dd><p>This option is similar to <code>bootstrap-lto</code>, but is intended for 255faster build by only using LTO in the final bootstrap stage. 256With ‘<samp>make profiledbootstrap</samp>’ the LTO frontend 257is trained only on generator files. 258</p> 259</dd> 260<dt>‘<samp>bootstrap-debug</samp>’</dt> 261<dd><p>Verifies that the compiler generates the same executable code, whether 262or not it is asked to emit debug information. To this end, this 263option builds stage2 host programs without debug information, and uses 264<samp>contrib/compare-debug</samp> to compare them with the stripped stage3 265object files. If <code>BOOT_CFLAGS</code> is overridden so as to not enable 266debug information, stage2 will have it, and stage3 won’t. This option 267is enabled by default when GCC bootstrapping is enabled, if 268<code>strip</code> can turn object files compiled with and without debug 269info into identical object files. In addition to better test 270coverage, this option makes default bootstraps faster and leaner. 271</p> 272</dd> 273<dt>‘<samp>bootstrap-debug-big</samp>’</dt> 274<dd><p>Rather than comparing stripped object files, as in 275<code>bootstrap-debug</code>, this option saves internal compiler dumps 276during stage2 and stage3 and compares them as well, which helps catch 277additional potential problems, but at a great cost in terms of disk 278space. It can be specified in addition to ‘<samp>bootstrap-debug</samp>’. 279</p> 280</dd> 281<dt>‘<samp>bootstrap-debug-lean</samp>’</dt> 282<dd><p>This option saves disk space compared with <code>bootstrap-debug-big</code>, 283but at the expense of some recompilation. Instead of saving the dumps 284of stage2 and stage3 until the final compare, it uses 285<samp>-fcompare-debug</samp> to generate, compare and remove the dumps 286during stage3, repeating the compilation that already took place in 287stage2, whose dumps were not saved. 288</p> 289</dd> 290<dt>‘<samp>bootstrap-debug-lib</samp>’</dt> 291<dd><p>This option tests executable code invariance over debug information 292generation on target libraries, just like <code>bootstrap-debug-lean</code> 293tests it on host programs. It builds stage3 libraries with 294<samp>-fcompare-debug</samp>, and it can be used along with any of the 295<code>bootstrap-debug</code> options above. 296</p> 297<p>There aren’t <code>-lean</code> or <code>-big</code> counterparts to this option 298because most libraries are only build in stage3, so bootstrap compares 299would not get significant coverage. Moreover, the few libraries built 300in stage2 are used in stage3 host programs, so we wouldn’t want to 301compile stage2 libraries with different options for comparison purposes. 302</p> 303</dd> 304<dt>‘<samp>bootstrap-debug-ckovw</samp>’</dt> 305<dd><p>Arranges for error messages to be issued if the compiler built on any 306stage is run without the option <samp>-fcompare-debug</samp>. This is 307useful to verify the full <samp>-fcompare-debug</samp> testing coverage. It 308must be used along with <code>bootstrap-debug-lean</code> and 309<code>bootstrap-debug-lib</code>. 310</p> 311</dd> 312<dt>‘<samp>bootstrap-cet</samp>’</dt> 313<dd><p>This option enables Intel CET for host tools during bootstrapping. 314‘<samp>BUILD_CONFIG=bootstrap-cet</samp>’ is equivalent to adding 315<samp>-fcf-protection</samp> to ‘<samp>BOOT_CFLAGS</samp>’. This option 316assumes that the host supports Intel CET (e.g. GNU assembler version 3172.30 or later). 318</p> 319</dd> 320<dt>‘<samp>bootstrap-time</samp>’</dt> 321<dd><p>Arranges for the run time of each program started by the GCC driver, 322built in any stage, to be logged to <samp>time.log</samp>, in the top level of 323the build tree. 324</p> 325</dd> 326</dl> 327 328<a name="Building-a-cross-compiler"></a> 329<h3 class="section">Building a cross compiler</h3> 330 331<p>When building a cross compiler, it is not generally possible to do a 3323-stage bootstrap of the compiler. This makes for an interesting problem 333as parts of GCC can only be built with GCC. 334</p> 335<p>To build a cross compiler, we recommend first building and installing a 336native compiler. You can then use the native GCC compiler to build the 337cross compiler. The installed native compiler needs to be GCC version 3382.95 or later. 339</p> 340<p>Assuming you have already installed a native copy of GCC and configured 341your cross compiler, issue the command <code>make</code>, which performs the 342following steps: 343</p> 344<ul> 345<li> Build host tools necessary to build the compiler. 346 347</li><li> Build target tools for use by the compiler such as binutils (bfd, 348binutils, gas, gprof, ld, and opcodes) 349if they have been individually linked or moved into the top level GCC source 350tree before configuring. 351 352</li><li> Build the compiler (single stage only). 353 354</li><li> Build runtime libraries using the compiler from the previous step. 355</li></ul> 356 357<p>Note that if an error occurs in any step the make process will exit. 358</p> 359<p>If you are not building GNU binutils in the same source tree as GCC, 360you will need a cross-assembler and cross-linker installed before 361configuring GCC. Put them in the directory 362<samp><var>prefix</var>/<var>target</var>/bin</samp>. Here is a table of the tools 363you should put in this directory: 364</p> 365<dl compact="compact"> 366<dt><samp>as</samp></dt> 367<dd><p>This should be the cross-assembler. 368</p> 369</dd> 370<dt><samp>ld</samp></dt> 371<dd><p>This should be the cross-linker. 372</p> 373</dd> 374<dt><samp>ar</samp></dt> 375<dd><p>This should be the cross-archiver: a program which can manipulate 376archive files (linker libraries) in the target machine’s format. 377</p> 378</dd> 379<dt><samp>ranlib</samp></dt> 380<dd><p>This should be a program to construct a symbol table in an archive file. 381</p></dd> 382</dl> 383 384<p>The installation of GCC will find these programs in that directory, 385and copy or link them to the proper place to for the cross-compiler to 386find them when run later. 387</p> 388<p>The easiest way to provide these files is to build the Binutils package. 389Configure it with the same <samp>--host</samp> and <samp>--target</samp> 390options that you use for configuring GCC, then build and install 391them. They install their executables automatically into the proper 392directory. Alas, they do not support all the targets that GCC 393supports. 394</p> 395<p>If you are not building a C library in the same source tree as GCC, 396you should also provide the target libraries and headers before 397configuring GCC, specifying the directories with 398<samp>--with-sysroot</samp> or <samp>--with-headers</samp> and 399<samp>--with-libs</samp>. Many targets also require “start files” such 400as <samp>crt0.o</samp> and 401<samp>crtn.o</samp> which are linked into each executable. There may be several 402alternatives for <samp>crt0.o</samp>, for use with profiling or other 403compilation options. Check your target’s definition of 404<code>STARTFILE_SPEC</code> to find out what start files it uses. 405</p> 406<a name="Building-in-parallel"></a> 407<h3 class="section">Building in parallel</h3> 408 409<p>GNU Make 3.80 and above, which is necessary to build GCC, support 410building in parallel. To activate this, you can use ‘<samp>make -j 2</samp>’ 411instead of ‘<samp>make</samp>’. You can also specify a bigger number, and 412in most cases using a value greater than the number of processors in 413your machine will result in fewer and shorter I/O latency hits, thus 414improving overall throughput; this is especially true for slow drives 415and network filesystems. 416</p> 417<a name="Building-the-Ada-compiler"></a> 418<h3 class="section">Building the Ada compiler</h3> 419 420<p>In order to build GNAT, the Ada compiler, you need a working GNAT 421compiler (GCC version 4.0 or later). 422This includes GNAT tools such as <code>gnatmake</code> and 423<code>gnatlink</code>, since the Ada front end is written in Ada and 424uses some GNAT-specific extensions. 425</p> 426<p>In order to build a cross compiler, it is suggested to install 427the new compiler as native first, and then use it to build the cross 428compiler. 429</p> 430<p><code>configure</code> does not test whether the GNAT installation works 431and has a sufficiently recent version; if too old a GNAT version is 432installed, the build will fail unless <samp>--enable-languages</samp> is 433used to disable building the Ada front end. 434</p> 435<p><code>ADA_INCLUDE_PATH</code> and <code>ADA_OBJECT_PATH</code> environment variables 436must not be set when building the Ada compiler, the Ada tools, or the 437Ada runtime libraries. You can check that your build environment is clean 438by verifying that ‘<samp>gnatls -v</samp>’ lists only one explicit path in each 439section. 440</p> 441<a name="Building-with-profile-feedback"></a> 442<h3 class="section">Building with profile feedback</h3> 443 444<p>It is possible to use profile feedback to optimize the compiler itself. This 445should result in a faster compiler binary. Experiments done on x86 using gcc 4463.3 showed approximately 7 percent speedup on compiling C programs. To 447bootstrap the compiler with profile feedback, use <code>make profiledbootstrap</code>. 448</p> 449<p>When ‘<samp>make profiledbootstrap</samp>’ is run, it will first build a <code>stage1</code> 450compiler. This compiler is used to build a <code>stageprofile</code> compiler 451instrumented to collect execution counts of instruction and branch 452probabilities. Training run is done by building <code>stagetrain</code> 453compiler. Finally a <code>stagefeedback</code> compiler is built 454using the information collected. 455</p> 456<p>Unlike standard bootstrap, several additional restrictions apply. The 457compiler used to build <code>stage1</code> needs to support a 64-bit integral type. 458It is recommended to only use GCC for this. 459</p> 460<p>On Linux/x86_64 hosts with some restrictions (no virtualization) it is 461also possible to do autofdo build with ‘<samp>make 462autoprofiledback</samp>’. This uses Linux perf to sample branches in the 463binary and then rebuild it with feedback derived from the profile. 464Linux perf and the <code>autofdo</code> toolkit needs to be installed for 465this. 466</p> 467<p>Only the profile from the current build is used, so when an error 468occurs it is recommended to clean before restarting. Otherwise 469the code quality may be much worse. 470</p> 471<hr /> 472<p> 473<p><a href="./index.html">Return to the GCC Installation page</a> 474</p> 475 476 477 478 479 480 481 482<hr> 483 484 485 486</body> 487</html> 488