diff options
Diffstat (limited to 'INSTALL/build.html')
| -rw-r--r-- | INSTALL/build.html | 380 |
1 files changed, 380 insertions, 0 deletions
diff --git a/INSTALL/build.html b/INSTALL/build.html new file mode 100644 index 000000000..644900fd6 --- /dev/null +++ b/INSTALL/build.html @@ -0,0 +1,380 @@ +<html lang="en"> +<head> +<title>Installing GCC: Building</title> +<meta http-equiv="Content-Type" content="text/html"> +<meta name="description" content="Installing GCC: Building"> +<meta name="generator" content="makeinfo 4.13"> +<link title="Top" rel="top" href="#Top"> +<link href="http://www.gnu.org/software/texinfo/" rel="generator-home" title="Texinfo Homepage"> +<!-- +Copyright (C) 1988, 1989, 1992, 1993, 1994, 1995, 1996, 1997, +1998, 1999, 2000, 2001, 2002, 2003, 2004, 2005, 2006, 2007, 2008, 2009, +2010 Free Software Foundation, Inc. + + Permission is granted to copy, distribute and/or modify this document +under the terms of the GNU Free Documentation License, Version 1.3 or +any later version published by the Free Software Foundation; with no +Invariant Sections, the Front-Cover texts being (a) (see below), and +with the Back-Cover Texts being (b) (see below). A copy of the +license is included in the section entitled "GNU Free Documentation License". + +(a) The FSF's Front-Cover Text is: + + A GNU Manual + +(b) The FSF's Back-Cover Text is: + + You have freedom to copy and modify this GNU Manual, like GNU + software. Copies published by the Free Software Foundation raise + funds for GNU development.--> +<meta http-equiv="Content-Style-Type" content="text/css"> +<style type="text/css"><!-- + pre.display { font-family:inherit } + pre.format { font-family:inherit } + pre.smalldisplay { font-family:inherit; font-size:smaller } + pre.smallformat { font-family:inherit; font-size:smaller } + pre.smallexample { font-size:smaller } + pre.smalllisp { font-size:smaller } + span.sc { font-variant:small-caps } + span.roman { font-family:serif; font-weight:normal; } + span.sansserif { font-family:sans-serif; font-weight:normal; } +--></style> +</head> +<body> +<h1 class="settitle">Installing GCC: Building</h1> +<a name="index-Installing-GCC_003a-Building-1"></a> +Now that GCC is configured, you are ready to build the compiler and +runtime libraries. + + <p>Some commands executed when making the compiler may fail (return a +nonzero status) and be ignored by <samp><span class="command">make</span></samp>. These failures, which +are often due to files that were not found, are expected, and can safely +be ignored. + + <p>It is normal to have compiler warnings when compiling certain files. +Unless you are a GCC developer, you can generally ignore these warnings +unless they cause compilation to fail. Developers should attempt to fix +any warnings encountered, however they can temporarily continue past +warnings-as-errors by specifying the configure flag +<samp><span class="option">--disable-werror</span></samp>. + + <p>On certain old systems, defining certain environment variables such as +<samp><span class="env">CC</span></samp> can interfere with the functioning of <samp><span class="command">make</span></samp>. + + <p>If you encounter seemingly strange errors when trying to build the +compiler in a directory other than the source directory, it could be +because you have previously configured the compiler in the source +directory. Make sure you have done all the necessary preparations. + + <p>If you build GCC on a BSD system using a directory stored in an old System +V file system, problems may occur in running <samp><span class="command">fixincludes</span></samp> if the +System V file system doesn't support symbolic links. These problems +result in a failure to fix the declaration of <code>size_t</code> in +<samp><span class="file">sys/types.h</span></samp>. If you find that <code>size_t</code> is a signed type and +that type mismatches occur, this could be the cause. + + <p>The solution is not to use such a directory for building GCC. + + <p>Similarly, when building from SVN or snapshots, or if you modify +<samp><span class="file">*.l</span></samp> files, you need the Flex lexical analyzer generator +installed. If you do not modify <samp><span class="file">*.l</span></samp> files, releases contain +the Flex-generated files and you do not need Flex installed to build +them. There is still one Flex-based lexical analyzer (part of the +build machinery, not of GCC itself) that is used even if you only +build the C front end. + + <p>When building from SVN or snapshots, or if you modify Texinfo +documentation, you need version 4.7 or later of Texinfo installed if you +want Info documentation to be regenerated. Releases contain Info +documentation pre-built for the unmodified documentation in the release. + +<h3 class="section"><a name="TOC0"></a>Building a native compiler</h3> + +<p>For a native build, the default configuration is to perform +a 3-stage bootstrap of the compiler when ‘<samp><span class="samp">make</span></samp>’ is invoked. +This will build the entire GCC system and ensure that it compiles +itself correctly. It can be disabled with the <samp><span class="option">--disable-bootstrap</span></samp> +parameter to ‘<samp><span class="samp">configure</span></samp>’, but bootstrapping is suggested because +the compiler will be tested more completely and could also have +better performance. + + <p>The bootstrapping process will complete the following steps: + + <ul> +<li>Build tools necessary to build the compiler. + + <li>Perform a 3-stage bootstrap of the compiler. This includes building +three times the target tools for use by the compiler such as binutils +(bfd, binutils, gas, gprof, ld, and opcodes) if they have been +individually linked or moved into the top level GCC source tree before +configuring. + + <li>Perform a comparison test of the stage2 and stage3 compilers. + + <li>Build runtime libraries using the stage3 compiler from the previous step. + + </ul> + + <p>If you are short on disk space you might consider ‘<samp><span class="samp">make +bootstrap-lean</span></samp>’ instead. The sequence of compilation is the +same described above, but object files from the stage1 and +stage2 of the 3-stage bootstrap of the compiler are deleted as +soon as they are no longer needed. + + <p>If you wish to use non-default GCC flags when compiling the stage2 +and stage3 compilers, set <code>BOOT_CFLAGS</code> on the command line when +doing ‘<samp><span class="samp">make</span></samp>’. For example, if you want to save additional space +during the bootstrap and in the final installation as well, you can +build the compiler binaries without debugging information as in the +following example. This will save roughly 40% of disk space both for +the bootstrap and the final installation. (Libraries will still contain +debugging information.) + +<pre class="smallexample"> make BOOT_CFLAGS='-O' bootstrap +</pre> + <p>You can place non-default optimization flags into <code>BOOT_CFLAGS</code>; they +are less well tested here than the default of ‘<samp><span class="samp">-g -O2</span></samp>’, but should +still work. In a few cases, you may find that you need to specify special +flags such as <samp><span class="option">-msoft-float</span></samp> here to complete the bootstrap; or, +if the native compiler miscompiles the stage1 compiler, you may need +to work around this, by choosing <code>BOOT_CFLAGS</code> to avoid the parts +of the stage1 compiler that were miscompiled, or by using ‘<samp><span class="samp">make +bootstrap4</span></samp>’ to increase the number of stages of bootstrap. + + <p><code>BOOT_CFLAGS</code> does not apply to bootstrapped target libraries. +Since these are always compiled with the compiler currently being +bootstrapped, you can use <code>CFLAGS_FOR_TARGET</code> to modify their +compilation flags, as for non-bootstrapped target libraries. +Again, if the native compiler miscompiles the stage1 compiler, you may +need to work around this by avoiding non-working parts of the stage1 +compiler. Use <code>STAGE1_TFLAGS</code> to this end. + + <p>If you used the flag <samp><span class="option">--enable-languages=...</span></samp> to restrict +the compilers to be built, only those you've actually enabled will be +built. This will of course only build those runtime libraries, for +which the particular compiler has been built. Please note, +that re-defining <samp><span class="env">LANGUAGES</span></samp> when calling ‘<samp><span class="samp">make</span></samp>’ +<strong>does not</strong> work anymore! + + <p>If the comparison of stage2 and stage3 fails, this normally indicates +that the stage2 compiler has compiled GCC incorrectly, and is therefore +a potentially serious bug which you should investigate and report. (On +a few systems, meaningful comparison of object files is impossible; they +always appear “different”. If you encounter this problem, you will +need to disable comparison in the <samp><span class="file">Makefile</span></samp>.) + + <p>If you do not want to bootstrap your compiler, you can configure with +<samp><span class="option">--disable-bootstrap</span></samp>. In particular cases, you may want to +bootstrap your compiler even if the target system is not the same as +the one you are building on: for example, you could build a +<code>powerpc-unknown-linux-gnu</code> toolchain on a +<code>powerpc64-unknown-linux-gnu</code> host. In this case, pass +<samp><span class="option">--enable-bootstrap</span></samp> to the configure script. + + <p><code>BUILD_CONFIG</code> can be used to bring in additional customization +to the build. It can be set to a whitespace-separated list of names. +For each such <code>NAME</code>, top-level <samp><span class="file">config/</span><code>NAME</code><span class="file">.mk</span></samp> will +be included by the top-level <samp><span class="file">Makefile</span></samp>, bringing in any settings +it contains. The default <code>BUILD_CONFIG</code> can be set using the +configure option <samp><span class="option">--with-build-config=</span><code>NAME</code><span class="option">...</span></samp>. Some +examples of supported build configurations are: + + <dl> +<dt>‘<samp><span class="samp">bootstrap-O1</span></samp>’<dd>Removes any <samp><span class="option">-O</span></samp>-started option from <code>BOOT_CFLAGS</code>, and adds +<samp><span class="option">-O1</span></samp> to it. ‘<samp><span class="samp">BUILD_CONFIG=bootstrap-O1</span></samp>’ is equivalent to +‘<samp><span class="samp">BOOT_CFLAGS='-g -O1'</span></samp>’. + + <br><dt>‘<samp><span class="samp">bootstrap-O3</span></samp>’<dd>Analogous to <code>bootstrap-O1</code>. + + <br><dt>‘<samp><span class="samp">bootstrap-lto</span></samp>’<dd>Enables Link-Time Optimization for host tools during bootstrapping. +‘<samp><span class="samp">BUILD_CONFIG=bootstrap-lto</span></samp>’ is equivalent to adding +<samp><span class="option">-flto</span></samp> to ‘<samp><span class="samp">BOOT_CFLAGS</span></samp>’. + + <br><dt>‘<samp><span class="samp">bootstrap-debug</span></samp>’<dd>Verifies that the compiler generates the same executable code, whether +or not it is asked to emit debug information. To this end, this +option builds stage2 host programs without debug information, and uses +<samp><span class="file">contrib/compare-debug</span></samp> to compare them with the stripped stage3 +object files. If <code>BOOT_CFLAGS</code> is overridden so as to not enable +debug information, stage2 will have it, and stage3 won't. This option +is enabled by default when GCC bootstrapping is enabled, if +<code>strip</code> can turn object files compiled with and without debug +info into identical object files. In addition to better test +coverage, this option makes default bootstraps faster and leaner. + + <br><dt>‘<samp><span class="samp">bootstrap-debug-big</span></samp>’<dd>Rather than comparing stripped object files, as in +<code>bootstrap-debug</code>, this option saves internal compiler dumps +during stage2 and stage3 and compares them as well, which helps catch +additional potential problems, but at a great cost in terms of disk +space. It can be specified in addition to ‘<samp><span class="samp">bootstrap-debug</span></samp>’. + + <br><dt>‘<samp><span class="samp">bootstrap-debug-lean</span></samp>’<dd>This option saves disk space compared with <code>bootstrap-debug-big</code>, +but at the expense of some recompilation. Instead of saving the dumps +of stage2 and stage3 until the final compare, it uses +<samp><span class="option">-fcompare-debug</span></samp> to generate, compare and remove the dumps +during stage3, repeating the compilation that already took place in +stage2, whose dumps were not saved. + + <br><dt>‘<samp><span class="samp">bootstrap-debug-lib</span></samp>’<dd>This option tests executable code invariance over debug information +generation on target libraries, just like <code>bootstrap-debug-lean</code> +tests it on host programs. It builds stage3 libraries with +<samp><span class="option">-fcompare-debug</span></samp>, and it can be used along with any of the +<code>bootstrap-debug</code> options above. + + <p>There aren't <code>-lean</code> or <code>-big</code> counterparts to this option +because most libraries are only build in stage3, so bootstrap compares +would not get significant coverage. Moreover, the few libraries built +in stage2 are used in stage3 host programs, so we wouldn't want to +compile stage2 libraries with different options for comparison purposes. + + <br><dt>‘<samp><span class="samp">bootstrap-debug-ckovw</span></samp>’<dd>Arranges for error messages to be issued if the compiler built on any +stage is run without the option <samp><span class="option">-fcompare-debug</span></samp>. This is +useful to verify the full <samp><span class="option">-fcompare-debug</span></samp> testing coverage. It +must be used along with <code>bootstrap-debug-lean</code> and +<code>bootstrap-debug-lib</code>. + + <br><dt>‘<samp><span class="samp">bootstrap-time</span></samp>’<dd>Arranges for the run time of each program started by the GCC driver, +built in any stage, to be logged to <samp><span class="file">time.log</span></samp>, in the top level of +the build tree. + + </dl> + +<h3 class="section"><a name="TOC1"></a>Building a cross compiler</h3> + +<p>When building a cross compiler, it is not generally possible to do a +3-stage bootstrap of the compiler. This makes for an interesting problem +as parts of GCC can only be built with GCC. + + <p>To build a cross compiler, we recommend first building and installing a +native compiler. You can then use the native GCC compiler to build the +cross compiler. The installed native compiler needs to be GCC version +2.95 or later. + + <p>If the cross compiler is to be built with support for the Java +programming language and the ability to compile .java source files is +desired, the installed native compiler used to build the cross +compiler needs to be the same GCC version as the cross compiler. In +addition the cross compiler needs to be configured with +<samp><span class="option">--with-ecj-jar=...</span></samp>. + + <p>Assuming you have already installed a native copy of GCC and configured +your cross compiler, issue the command <samp><span class="command">make</span></samp>, which performs the +following steps: + + <ul> +<li>Build host tools necessary to build the compiler. + + <li>Build target tools for use by the compiler such as binutils (bfd, +binutils, gas, gprof, ld, and opcodes) +if they have been individually linked or moved into the top level GCC source +tree before configuring. + + <li>Build the compiler (single stage only). + + <li>Build runtime libraries using the compiler from the previous step. +</ul> + + <p>Note that if an error occurs in any step the make process will exit. + + <p>If you are not building GNU binutils in the same source tree as GCC, +you will need a cross-assembler and cross-linker installed before +configuring GCC. Put them in the directory +<samp><var>prefix</var><span class="file">/</span><var>target</var><span class="file">/bin</span></samp>. Here is a table of the tools +you should put in this directory: + + <dl> +<dt><samp><span class="file">as</span></samp><dd>This should be the cross-assembler. + + <br><dt><samp><span class="file">ld</span></samp><dd>This should be the cross-linker. + + <br><dt><samp><span class="file">ar</span></samp><dd>This should be the cross-archiver: a program which can manipulate +archive files (linker libraries) in the target machine's format. + + <br><dt><samp><span class="file">ranlib</span></samp><dd>This should be a program to construct a symbol table in an archive file. +</dl> + + <p>The installation of GCC will find these programs in that directory, +and copy or link them to the proper place to for the cross-compiler to +find them when run later. + + <p>The easiest way to provide these files is to build the Binutils package. +Configure it with the same <samp><span class="option">--host</span></samp> and <samp><span class="option">--target</span></samp> +options that you use for configuring GCC, then build and install +them. They install their executables automatically into the proper +directory. Alas, they do not support all the targets that GCC +supports. + + <p>If you are not building a C library in the same source tree as GCC, +you should also provide the target libraries and headers before +configuring GCC, specifying the directories with +<samp><span class="option">--with-sysroot</span></samp> or <samp><span class="option">--with-headers</span></samp> and +<samp><span class="option">--with-libs</span></samp>. Many targets also require “start files” such +as <samp><span class="file">crt0.o</span></samp> and +<samp><span class="file">crtn.o</span></samp> which are linked into each executable. There may be several +alternatives for <samp><span class="file">crt0.o</span></samp>, for use with profiling or other +compilation options. Check your target's definition of +<code>STARTFILE_SPEC</code> to find out what start files it uses. + +<h3 class="section"><a name="TOC2"></a>Building in parallel</h3> + +<p>GNU Make 3.80 and above, which is necessary to build GCC, support +building in parallel. To activate this, you can use ‘<samp><span class="samp">make -j 2</span></samp>’ +instead of ‘<samp><span class="samp">make</span></samp>’. You can also specify a bigger number, and +in most cases using a value greater than the number of processors in +your machine will result in fewer and shorter I/O latency hits, thus +improving overall throughput; this is especially true for slow drives +and network filesystems. + +<h3 class="section"><a name="TOC3"></a>Building the Ada compiler</h3> + +<p>In order to build GNAT, the Ada compiler, you need a working GNAT +compiler (GCC version 4.0 or later). +This includes GNAT tools such as <samp><span class="command">gnatmake</span></samp> and +<samp><span class="command">gnatlink</span></samp>, since the Ada front end is written in Ada and +uses some GNAT-specific extensions. + + <p>In order to build a cross compiler, it is suggested to install +the new compiler as native first, and then use it to build the cross +compiler. + + <p><samp><span class="command">configure</span></samp> does not test whether the GNAT installation works +and has a sufficiently recent version; if too old a GNAT version is +installed, the build will fail unless <samp><span class="option">--enable-languages</span></samp> is +used to disable building the Ada front end. + + <p><samp><span class="env">ADA_INCLUDE_PATH</span></samp> and <samp><span class="env">ADA_OBJECT_PATH</span></samp> environment variables +must not be set when building the Ada compiler, the Ada tools, or the +Ada runtime libraries. You can check that your build environment is clean +by verifying that ‘<samp><span class="samp">gnatls -v</span></samp>’ lists only one explicit path in each +section. + +<h3 class="section"><a name="TOC4"></a>Building with profile feedback</h3> + +<p>It is possible to use profile feedback to optimize the compiler itself. This +should result in a faster compiler binary. Experiments done on x86 using gcc +3.3 showed approximately 7 percent speedup on compiling C programs. To +bootstrap the compiler with profile feedback, use <code>make profiledbootstrap</code>. + + <p>When ‘<samp><span class="samp">make profiledbootstrap</span></samp>’ is run, it will first build a <code>stage1</code> +compiler. This compiler is used to build a <code>stageprofile</code> compiler +instrumented to collect execution counts of instruction and branch +probabilities. Then runtime libraries are compiled with profile collected. +Finally a <code>stagefeedback</code> compiler is built using the information collected. + + <p>Unlike standard bootstrap, several additional restrictions apply. The +compiler used to build <code>stage1</code> needs to support a 64-bit integral type. +It is recommended to only use GCC for this. Also parallel make is currently +not supported since collisions in profile collecting may occur. + + <p><hr /> +<p><a href="./index.html">Return to the GCC Installation page</a> + +<!-- ***Testing***************************************************************** --> +<!-- ***Final install*********************************************************** --> +<!-- ***Binaries**************************************************************** --> +<!-- ***Specific**************************************************************** --> +<!-- ***Old documentation****************************************************** --> +<!-- ***GFDL******************************************************************** --> +<!-- *************************************************************************** --> +<!-- Part 6 The End of the Document --> +</body></html> + |