| 1 | <html lang="en"><head>
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| 2 | <title>Installing GCC: Building</title>
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| 3 | <meta http-equiv="Content-Type" content="text/html">
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| 4 | <meta name=description content="Installing GCC: Building">
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| 5 | <meta name=generator content="makeinfo 4.0">
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| 6 | <link href="http://texinfo.org/" rel=generator-home>
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| 7 | </head><body>
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| 8 |
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| 9 | <p>N<p>ow that GCC is configured, you are ready to build the compiler and
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| 10 | runtime libraries.
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| 11 |
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| 12 | <p>We <strong>highly</strong> recommend that GCC be built using GNU make;
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| 13 | other versions may work, then again they might not.
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| 14 | GNU make is required for compiling GNAT (the Ada compiler) and the Java
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| 15 | runtime library.
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| 16 |
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| 17 | <p>(For example, many broken versions of make will fail if you use the
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| 18 | recommended setup where <var>objdir</var> is different from <var>srcdir</var>.
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| 19 | Other broken versions may recompile parts of the compiler when
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| 20 | installing the compiler.)
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| 21 |
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| 22 | <p>Some commands executed when making the compiler may fail (return a
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| 23 | nonzero status) and be ignored by <code>make</code>. These failures, which
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| 24 | are often due to files that were not found, are expected, and can safely
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| 25 | be ignored.
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| 26 |
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| 27 | <p>It is normal to have compiler warnings when compiling certain files.
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| 28 | Unless you are a GCC developer, you can generally ignore these warnings
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| 29 | unless they cause compilation to fail.
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| 30 |
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| 31 | <p>On certain old systems, defining certain environment variables such as
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| 32 | <code>CC</code> can interfere with the functioning of <code>make</code>.
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| 33 |
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| 34 | <p>If you encounter seemingly strange errors when trying to build the
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| 35 | compiler in a directory other than the source directory, it could be
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| 36 | because you have previously configured the compiler in the source
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| 37 | directory. Make sure you have done all the necessary preparations.
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| 38 |
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| 39 | <p>If you build GCC on a BSD system using a directory stored in an old System
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| 40 | V file system, problems may occur in running <code>fixincludes</code> if the
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| 41 | System V file system doesn't support symbolic links. These problems
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| 42 | result in a failure to fix the declaration of <code>size_t</code> in
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| 43 | <code>sys/types.h</code>. If you find that <code>size_t</code> is a signed type and
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| 44 | that type mismatches occur, this could be the cause.
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| 45 |
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| 46 | <p>The solution is not to use such a directory for building GCC.
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| 47 |
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| 48 | <p>When building from CVS or snapshots, or if you modify parser sources,
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| 49 | you need the Bison parser generator installed. Any version 1.25 or
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| 50 | later should work; older versions may also work. If you do not modify
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| 51 | parser sources, releases contain the Bison-generated files and you do
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| 52 | not need Bison installed to build them.
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| 53 |
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| 54 | <p>When building from CVS or snapshots, or if you modify Texinfo
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| 55 | documentation, you need version 4.1 or later of Texinfo installed if you
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| 56 | want Info documentation to be regenerated. Releases contain Info
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| 57 | documentation pre-built for the unmodified documentation in the release.
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| 58 |
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| 59 | <h2><a name="TOC0">Building a native compiler</h2>
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| 60 |
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| 61 | <p>For a native build issue the command <code>make bootstrap</code>. This
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| 62 | will build the entire GCC system, which includes the following steps:
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| 63 |
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| 64 | <ul>
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| 65 | <li>Build host tools necessary to build the compiler such as texinfo, bison,
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| 66 | gperf.
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| 67 |
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| 68 | <li>Build target tools for use by the compiler such as binutils (bfd,
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| 69 | binutils, gas, gprof, ld, and opcodes)
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| 70 | if they have been individually linked
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| 71 | or moved into the top level GCC source tree before configuring.
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| 72 |
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| 73 | <li>Perform a 3-stage bootstrap of the compiler.
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| 74 |
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| 75 | <li>Perform a comparison test of the stage2 and stage3 compilers.
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| 76 |
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| 77 | <li>Build runtime libraries using the stage3 compiler from the previous step.
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| 78 |
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| 79 | </ul>
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| 80 |
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| 81 | <p>If you are short on disk space you might consider <code>make
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| 82 | bootstrap-lean</code> instead. This is identical to <code>make
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| 83 | bootstrap</code> except that object files from the stage1 and
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| 84 | stage2 of the 3-stage bootstrap of the compiler are deleted as
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| 85 | soon as they are no longer needed.
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| 86 |
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| 87 | <p>If you want to save additional space during the bootstrap and in
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| 88 | the final installation as well, you can build the compiler binaries
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| 89 | without debugging information as in the following example. This will save
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| 90 | roughly 40% of disk space both for the bootstrap and the final installation.
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| 91 | (Libraries will still contain debugging information.)
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| 92 |
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| 93 | <pre> make CFLAGS='-O' LIBCFLAGS='-g -O2' \
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| 94 | LIBCXXFLAGS='-g -O2 -fno-implicit-templates' bootstrap
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| 95 | </pre>
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| 96 |
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| 97 | <p>If you wish to use non-default GCC flags when compiling the stage2 and
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| 98 | stage3 compilers, set <code>BOOT_CFLAGS</code> on the command line when doing
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| 99 | <code>make bootstrap</code>. Non-default optimization flags are less well
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| 100 | tested here than the default of <code>-g -O2</code>, but should still work.
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| 101 | In a few cases, you may find that you need to specify special flags such
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| 102 | as <code>-msoft-float</code> here to complete the bootstrap; or, if the
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| 103 | native compiler miscompiles the stage1 compiler, you may need to work
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| 104 | around this, by choosing <code>BOOT_CFLAGS</code> to avoid the parts of the
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| 105 | stage1 compiler that were miscompiled, or by using <code>make
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| 106 | bootstrap4</code> to increase the number of stages of bootstrap.
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| 107 |
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| 108 | <p>If you used the flag <code>--enable-languages=<small>...</small></code> to restrict
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| 109 | the compilers to be built, only those you've actually enabled will be
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| 110 | built. This will of course only build those runtime libraries, for
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| 111 | which the particular compiler has been built. Please note,
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| 112 | that re-defining <code>LANGUAGES</code> when calling <code>make bootstrap</code>
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| 113 | <strong>does not</strong> work anymore!
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| 114 |
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| 115 | <p>If the comparison of stage2 and stage3 fails, this normally indicates
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| 116 | that the stage2 compiler has compiled GCC incorrectly, and is therefore
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| 117 | a potentially serious bug which you should investigate and report. (On
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| 118 | a few systems, meaningful comparison of object files is impossible; they
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| 119 | always appear "different". If you encounter this problem, you will
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| 120 | need to disable comparison in the <code>Makefile</code>.)
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| 121 |
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| 122 | <h2><a name="TOC1">Building a cross compiler</h2>
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| 123 |
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| 124 | <p>We recommend reading the
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| 125 | <a href="http://www.objsw.com/CrossGCC/">crossgcc FAQ</a>
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| 126 | for information about building cross compilers.
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| 127 |
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| 128 | <p>When building a cross compiler, it is not generally possible to do a
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| 129 | 3-stage bootstrap of the compiler. This makes for an interesting problem
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| 130 | as parts of GCC can only be built with GCC.
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| 131 |
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| 132 | <p>To build a cross compiler, we first recommend building and installing a
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| 133 | native compiler. You can then use the native GCC compiler to build the
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| 134 | cross compiler. The installed native compiler needs to be GCC version
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| 135 | 2.95 or later.
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| 136 |
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| 137 | <p>Assuming you have already installed a native copy of GCC and configured
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| 138 | your cross compiler, issue the command <code>make</code>, which performs the
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| 139 | following steps:
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| 140 |
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| 141 | <ul>
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| 142 | <li>Build host tools necessary to build the compiler such as texinfo, bison,
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| 143 | gperf.
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| 144 |
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| 145 | <li>Build target tools for use by the compiler such as binutils (bfd,
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| 146 | binutils, gas, gprof, ld, and opcodes)
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| 147 | if they have been individually linked or moved into the top level GCC source
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| 148 | tree before configuring.
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| 149 |
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| 150 | <li>Build the compiler (single stage only).
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| 151 |
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| 152 | <li>Build runtime libraries using the compiler from the previous step.
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| 153 | </ul>
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| 154 |
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| 155 | <p>Note that if an error occurs in any step the make process will exit.
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| 156 |
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| 157 | <h2><a name="TOC2">Building in parallel</h2>
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| 158 |
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| 159 | <p>If you have a multiprocessor system you can use <code>make bootstrap
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| 160 | MAKE="make -j 2" -j 2</code> or just <code>make -j 2 bootstrap</code>
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| 161 | for GNU Make 3.79 and above instead of just <code>make bootstrap</code>
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| 162 | when building GCC. You can use a bigger number instead of two if
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| 163 | you like. In most cases, it won't help to use a number bigger than
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| 164 | the number of processors in your machine.
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| 165 |
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| 166 | <h2><a name="TOC3">Building the Ada compiler</h2>
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| 167 |
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| 168 | <p>In order to build GNAT, the Ada compiler, you need a working GNAT
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| 169 | compiler (GNAT version 3.13 or later, or GCC version 3.1 or later),
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| 170 | since the Ada front end is written in Ada (with some
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| 171 | GNAT-specific extensions), and GNU make.
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| 172 |
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| 173 | <p>However, you do not need a full installation of GNAT, just the GNAT
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| 174 | binary <code>gnat1</code>, a copy of <code>gnatbind</code>, and a compiler driver
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| 175 | which can deal with Ada input (by invoking the <code>gnat1</code> binary).
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| 176 | You can specify this compiler driver by setting the <code>ADAC</code>
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| 177 | environment variable at the configure step. <code>configure</code> can
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| 178 | detect the driver automatically if it has got a common name such as
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| 179 | <code>gcc</code> or <code>gnatgcc</code>. Of course, you still need a working
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| 180 | C compiler (the compiler driver can be different or not).
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| 181 | <code>configure</code> does not test whether the GNAT installation works
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| 182 | and has a sufficiently recent version; if too old a GNAT version is
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| 183 | installed, the build will fail unless <code>--enable-languages</code> is
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| 184 | used to disable building the Ada front end.
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| 185 |
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| 186 | <p>Additional build tools (such as <code>gnatmake</code>) or a working GNAT
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| 187 | run-time library installation are usually <em>not</em> required. However,
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| 188 | if you want to bootstrap the compiler using a minimal version of GNAT,
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| 189 | you have to issue the following commands before invoking <code>make
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| 190 | bootstrap</code> (this assumes that you start with an unmodified and consistent
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| 191 | source distribution):
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| 192 |
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| 193 | <pre> cd <var>srcdir</var>/gcc/ada
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| 194 | touch treeprs.ads [es]info.h nmake.ad[bs]
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| 195 | </pre>
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| 196 |
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| 197 | <p>At the moment, the GNAT library and several tools for GNAT are not built
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| 198 | by <code>make bootstrap</code>. You have to invoke
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| 199 | <code>make gnatlib_and_tools</code> in the <code><var>objdir</var>/gcc</code>
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| 200 | subdirectory before proceeding with the next steps.
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| 201 |
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| 202 | <p>For example, you can build a native Ada compiler by issuing the
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| 203 | following commands (assuming <code>make</code> is GNU make):
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| 204 |
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| 205 | <pre> cd <var>objdir</var>
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| 206 | <var>srcdir</var>/configure --enable-languages=c,ada
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| 207 | cd <var>srcdir</var>/gcc/ada
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| 208 | touch treeprs.ads [es]info.h nmake.ad[bs]
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| 209 | cd <var>objdir</var>
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| 210 | make bootstrap
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| 211 | cd gcc
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| 212 | make gnatlib_and_tools
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| 213 | cd ..
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| 214 | </pre>
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| 215 |
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| 216 | <p>Currently, when compiling the Ada front end, you cannot use the parallel
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| 217 | build feature described in the previous section.
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| 218 |
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| 219 | <hr />
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| 220 | <p>
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| 221 | <a href="./index.html">Return to the GCC Installation page</a>
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| 222 |
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| 223 | </body></html>
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| 224 |
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