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| 2 | <head>
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| 3 | <title>Installing GCC: Building</title>
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| 4 | <meta http-equiv="Content-Type" content="text/html">
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| 5 | <meta name="description" content="Installing GCC: Building">
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| 6 | <meta name="generator" content="makeinfo 4.5">
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| 7 | <link href="http://www.gnu.org/software/texinfo/" rel="generator-home">
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| 8 | <!--
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| 9 | Copyright © 1988, 1989, 1992, 1993, 1994, 1995, 1996, 1997, 1998,
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| 10 | 1999, 2000, 2001, 2002, 2003 Free Software Foundation, Inc.
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| 11 | <br><p>
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| 12 | <p>Permission is granted to copy, distribute and/or modify this document
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| 13 | under the terms of the GNU Free Documentation License, Version 1.2 or
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| 14 | any later version published by the Free Software Foundation; with no
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| 15 | Invariant Sections, the Front-Cover texts being (a) (see below), and
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| 16 | with the Back-Cover Texts being (b) (see below). A copy of the
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| 17 | license is included in the section entitled "<a href="./gfdl.html">GNU Free Documentation License</a>".
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| 18 |
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| 19 | <p>(a) The FSF's Front-Cover Text is:
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| 20 |
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| 21 | <p>A GNU Manual
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| 22 |
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| 23 | <p>(b) The FSF's Back-Cover Text is:
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| 24 |
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| 25 | <p>You have freedom to copy and modify this GNU Manual, like GNU
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| 26 | software. Copies published by the Free Software Foundation raise
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| 27 | funds for GNU development.-->
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| 28 | </head>
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| 29 | <body>
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| 30 | <h1 class="settitle">Installing GCC: Building</h1>
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| 31 | Now that GCC is configured, you are ready to build the compiler and
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| 32 | runtime libraries.
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| 33 |
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| 34 | <p>We <strong>highly</strong> recommend that GCC be built using GNU make;
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| 35 | other versions may work, then again they might not.
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| 36 | GNU make is required for compiling GNAT (the Ada compiler) and the Java
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| 37 | runtime library.
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| 38 |
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| 39 | <p>(For example, many broken versions of make will fail if you use the
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| 40 | recommended setup where <var>objdir</var> is different from <var>srcdir</var>.
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| 41 | Other broken versions may recompile parts of the compiler when
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| 42 | installing the compiler.)
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| 43 |
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| 44 | <p>Some commands executed when making the compiler may fail (return a
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| 45 | nonzero status) and be ignored by <code>make</code>. These failures, which
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| 46 | are often due to files that were not found, are expected, and can safely
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| 47 | be ignored.
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| 48 |
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| 49 | <p>It is normal to have compiler warnings when compiling certain files.
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| 50 | Unless you are a GCC developer, you can generally ignore these warnings
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| 51 | unless they cause compilation to fail.
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| 52 |
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| 53 | <p>On certain old systems, defining certain environment variables such as
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| 54 | <code>CC</code> can interfere with the functioning of <code>make</code>.
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| 55 |
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| 56 | <p>If you encounter seemingly strange errors when trying to build the
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| 57 | compiler in a directory other than the source directory, it could be
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| 58 | because you have previously configured the compiler in the source
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| 59 | directory. Make sure you have done all the necessary preparations.
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| 60 |
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| 61 | <p>If you build GCC on a BSD system using a directory stored in an old System
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| 62 | V file system, problems may occur in running <code>fixincludes</code> if the
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| 63 | System V file system doesn't support symbolic links. These problems
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| 64 | result in a failure to fix the declaration of <code>size_t</code> in
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| 65 | <code>sys/types.h</code>. If you find that <code>size_t</code> is a signed type and
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| 66 | that type mismatches occur, this could be the cause.
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| 67 |
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| 68 | <p>The solution is not to use such a directory for building GCC.
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| 69 |
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| 70 | <p>When building from CVS or snapshots, or if you modify parser sources,
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| 71 | you need the Bison parser generator installed. Any version 1.25 or
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| 72 | later should work; older versions may also work. If you do not modify
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| 73 | parser sources, releases contain the Bison-generated files and you do
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| 74 | not need Bison installed to build them.
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| 75 |
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| 76 | <p>When building from CVS or snapshots, or if you modify Texinfo
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| 77 | documentation, you need version 4.2 or later of Texinfo installed if you
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| 78 | want Info documentation to be regenerated. Releases contain Info
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| 79 | documentation pre-built for the unmodified documentation in the release.
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| 80 |
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| 81 | <h3 class="section"><a name="TOC0"></a>Building a native compiler</h3>
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| 82 |
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| 83 | <p>For a native build issue the command <code>make bootstrap</code>. This
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| 84 | will build the entire GCC system, which includes the following steps:
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| 85 |
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| 86 | <ul>
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| 87 | <li>Build host tools necessary to build the compiler such as texinfo, bison,
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| 88 | gperf.
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| 89 |
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| 90 | <li>Build target tools for use by the compiler such as binutils (bfd,
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| 91 | binutils, gas, gprof, ld, and opcodes)
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| 92 | if they have been individually linked
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| 93 | or moved into the top level GCC source tree before configuring.
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| 94 |
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| 95 | <li>Perform a 3-stage bootstrap of the compiler.
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| 96 |
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| 97 | <li>Perform a comparison test of the stage2 and stage3 compilers.
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| 98 |
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| 99 | <li>Build runtime libraries using the stage3 compiler from the previous step.
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| 100 |
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| 101 | </ul>
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| 102 |
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| 103 | <p>If you are short on disk space you might consider <code>make
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| 104 | bootstrap-lean</code> instead. This is identical to <code>make
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| 105 | bootstrap</code> except that object files from the stage1 and
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| 106 | stage2 of the 3-stage bootstrap of the compiler are deleted as
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| 107 | soon as they are no longer needed.
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| 108 |
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| 109 | <p>If you want to save additional space during the bootstrap and in
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| 110 | the final installation as well, you can build the compiler binaries
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| 111 | without debugging information as in the following example. This will save
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| 112 | roughly 40% of disk space both for the bootstrap and the final installation.
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| 113 | (Libraries will still contain debugging information.)
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| 114 |
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| 115 | <pre class="example"> make CFLAGS='-O' LIBCFLAGS='-g -O2' \
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| 116 | LIBCXXFLAGS='-g -O2 -fno-implicit-templates' bootstrap
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| 117 | </pre>
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| 118 |
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| 119 | <p>If you wish to use non-default GCC flags when compiling the stage2 and
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| 120 | stage3 compilers, set <code>BOOT_CFLAGS</code> on the command line when doing
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| 121 | <code>make bootstrap</code>. Non-default optimization flags are less well
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| 122 | tested here than the default of <code>-g -O2</code>, but should still work.
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| 123 | In a few cases, you may find that you need to specify special flags such
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| 124 | as <code>-msoft-float</code> here to complete the bootstrap; or, if the
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| 125 | native compiler miscompiles the stage1 compiler, you may need to work
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| 126 | around this, by choosing <code>BOOT_CFLAGS</code> to avoid the parts of the
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| 127 | stage1 compiler that were miscompiled, or by using <code>make
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| 128 | bootstrap4</code> to increase the number of stages of bootstrap.
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| 129 |
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| 130 | <p>If you used the flag <code>--enable-languages=...</code> to restrict
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| 131 | the compilers to be built, only those you've actually enabled will be
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| 132 | built. This will of course only build those runtime libraries, for
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| 133 | which the particular compiler has been built. Please note,
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| 134 | that re-defining <code>LANGUAGES</code> when calling <code>make bootstrap</code>
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| 135 | <strong>does not</strong> work anymore!
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| 136 |
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| 137 | <p>If the comparison of stage2 and stage3 fails, this normally indicates
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| 138 | that the stage2 compiler has compiled GCC incorrectly, and is therefore
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| 139 | a potentially serious bug which you should investigate and report. (On
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| 140 | a few systems, meaningful comparison of object files is impossible; they
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| 141 | always appear "different". If you encounter this problem, you will
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| 142 | need to disable comparison in the <code>Makefile</code>.)
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| 143 |
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| 144 | <h3 class="section"><a name="TOC1"></a>Building a cross compiler</h3>
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| 145 |
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| 146 | <p>We recommend reading the
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| 147 | <a href="http://www.objsw.com/CrossGCC/">crossgcc FAQ</a>
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| 148 | for information about building cross compilers.
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| 149 |
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| 150 | <p>When building a cross compiler, it is not generally possible to do a
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| 151 | 3-stage bootstrap of the compiler. This makes for an interesting problem
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| 152 | as parts of GCC can only be built with GCC.
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| 153 |
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| 154 | <p>To build a cross compiler, we first recommend building and installing a
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| 155 | native compiler. You can then use the native GCC compiler to build the
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| 156 | cross compiler. The installed native compiler needs to be GCC version
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| 157 | 2.95 or later.
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| 158 |
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| 159 | <p>Assuming you have already installed a native copy of GCC and configured
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| 160 | your cross compiler, issue the command <code>make</code>, which performs the
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| 161 | following steps:
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| 162 |
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| 163 | <ul>
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| 164 | <li>Build host tools necessary to build the compiler such as texinfo, bison,
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| 165 | gperf.
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| 166 |
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| 167 | <li>Build target tools for use by the compiler such as binutils (bfd,
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| 168 | binutils, gas, gprof, ld, and opcodes)
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| 169 | if they have been individually linked or moved into the top level GCC source
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| 170 | tree before configuring.
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| 171 |
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| 172 | <li>Build the compiler (single stage only).
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| 173 |
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| 174 | <li>Build runtime libraries using the compiler from the previous step.
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| 175 | </ul>
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| 176 |
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| 177 | <p>Note that if an error occurs in any step the make process will exit.
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| 178 |
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| 179 | <h3 class="section"><a name="TOC2"></a>Building in parallel</h3>
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| 180 |
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| 181 | <p>You can use <code>make bootstrap MAKE="make -j 2" -j 2</code>, or just
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| 182 | <code>make -j 2 bootstrap</code> for GNU Make 3.79 and above, instead of
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| 183 | <code>make bootstrap</code> to build GCC in parallel.
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| 184 | You can also specify a bigger number, and in most cases using a value
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| 185 | greater than the number of processors in your machine will result in
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| 186 | fewer and shorter I/O latency hits, thus improving overall throughput;
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| 187 | this is especially true for slow drives and network filesystems.
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| 188 |
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| 189 | <h3 class="section"><a name="TOC3"></a>Building the Ada compiler</h3>
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| 190 |
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| 191 | <p>In order to build GNAT, the Ada compiler, you need a working GNAT
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| 192 | compiler (GNAT version 3.13 or later, or GCC version 3.1 or later),
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| 193 | since the Ada front end is written in Ada (with some
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| 194 | GNAT-specific extensions), and GNU make.
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| 195 |
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| 196 | <p>However, you do not need a full installation of GNAT, just the GNAT
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| 197 | binary <code>gnat1</code>, a copy of <code>gnatbind</code>, and a compiler driver
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| 198 | which can deal with Ada input (by invoking the <code>gnat1</code> binary).
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| 199 | You can specify this compiler driver by setting the <code>ADAC</code>
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| 200 | environment variable at the configure step. <code>configure</code> can
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| 201 | detect the driver automatically if it has got a common name such as
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| 202 | <code>gcc</code> or <code>gnatgcc</code>. Of course, you still need a working
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| 203 | C compiler (the compiler driver can be different or not).
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| 204 | <code>configure</code> does not test whether the GNAT installation works
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| 205 | and has a sufficiently recent version; if too old a GNAT version is
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| 206 | installed, the build will fail unless <code>--enable-languages</code> is
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| 207 | used to disable building the Ada front end.
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| 208 |
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| 209 | <p>Additional build tools (such as <code>gnatmake</code>) or a working GNAT
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| 210 | run-time library installation are usually <em>not</em> required. However,
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| 211 | if you want to bootstrap the compiler using a minimal version of GNAT,
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| 212 | you have to issue the following commands before invoking <code>make
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| 213 | bootstrap</code> (this assumes that you start with an unmodified and consistent
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| 214 | source distribution):
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| 215 |
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| 216 | <pre class="example"> cd <var>srcdir</var>/gcc/ada
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| 217 | touch treeprs.ads [es]info.h nmake.ad[bs]
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| 218 | </pre>
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| 219 |
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| 220 | <p>At the moment, the GNAT library and several tools for GNAT are not built
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| 221 | by <code>make bootstrap</code>. You have to invoke
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| 222 | <code>make gnatlib_and_tools</code> in the <code></code><var>objdir</var><code>/gcc</code>
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| 223 | subdirectory before proceeding with the next steps.
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| 224 |
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| 225 | <p>For example, you can build a native Ada compiler by issuing the
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| 226 | following commands (assuming <code>make</code> is GNU make):
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| 227 |
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| 228 | <pre class="example"> cd <var>objdir</var>
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| 229 | <var>srcdir</var>/configure --enable-languages=c,ada
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| 230 | cd <var>srcdir</var>/gcc/ada
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| 231 | touch treeprs.ads [es]info.h nmake.ad[bs]
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| 232 | cd <var>objdir</var>
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| 233 | make bootstrap
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| 234 | cd gcc
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| 235 | make gnatlib_and_tools
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| 236 | cd ..
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| 237 | </pre>
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| 238 |
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| 239 | <p>Currently, when compiling the Ada front end, you cannot use the parallel
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| 240 | build feature described in the previous section.
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| 241 |
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| 242 | <hr />
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| 243 | <p>
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| 244 | <a href="./index.html">Return to the GCC Installation page</a>
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| 245 |
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| 246 | </body></html>
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| 247 |
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