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239 lines
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HTML
4 years ago
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<title>Environment Variables - Using the GNU Compiler Collection (GCC)</title>
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<meta name="description" content="Using the GNU Compiler Collection (GCC)">
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<link rel="up" href="Invoking-GCC.html#Invoking-GCC" title="Invoking GCC">
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<link rel="prev" href="Code-Gen-Options.html#Code-Gen-Options" title="Code Gen Options">
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<link rel="next" href="Precompiled-Headers.html#Precompiled-Headers" title="Precompiled Headers">
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<link href="http://www.gnu.org/software/texinfo/" rel="generator-home" title="Texinfo Homepage">
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Copyright (C) 1988-2015 Free Software Foundation, Inc.
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Permission is granted to copy, distribute and/or modify this document
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under the terms of the GNU Free Documentation License, Version 1.3 or
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any later version published by the Free Software Foundation; with the
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Invariant Sections being ``Funding Free Software'', the Front-Cover
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(see below). A copy of the license is included in the section entitled
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``GNU Free Documentation License''.
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(a) The FSF's Front-Cover Text is:
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A GNU Manual
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(b) The FSF's Back-Cover Text is:
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</head>
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<body>
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<div class="node">
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<a name="Environment-Variables"></a>
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<p>
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Next: <a rel="next" accesskey="n" href="Precompiled-Headers.html#Precompiled-Headers">Precompiled Headers</a>,
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Previous: <a rel="previous" accesskey="p" href="Code-Gen-Options.html#Code-Gen-Options">Code Gen Options</a>,
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Up: <a rel="up" accesskey="u" href="Invoking-GCC.html#Invoking-GCC">Invoking GCC</a>
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<hr>
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</div>
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<h3 class="section">3.19 Environment Variables Affecting GCC</h3>
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<p><a name="index-environment-variables-2836"></a>
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<!-- man begin ENVIRONMENT -->
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This section describes several environment variables that affect how GCC
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operates. Some of them work by specifying directories or prefixes to use
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when searching for various kinds of files. Some are used to specify other
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aspects of the compilation environment.
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<p>Note that you can also specify places to search using options such as
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<samp><span class="option">-B</span></samp>, <samp><span class="option">-I</span></samp> and <samp><span class="option">-L</span></samp> (see <a href="Directory-Options.html#Directory-Options">Directory Options</a>). These
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take precedence over places specified using environment variables, which
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in turn take precedence over those specified by the configuration of GCC.
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See <a href="../gccint/Driver.html#Driver">Controlling the Compilation Driver <samp><span class="file">gcc</span></samp></a>.
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<dl>
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<dt><samp><span class="env">LANG</span></samp><dt><samp><span class="env">LC_CTYPE</span></samp><dd><!-- @itemx LC_COLLATE -->
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<dt><samp><span class="env">LC_MESSAGES</span></samp><dd><!-- @itemx LC_MONETARY -->
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<!-- @itemx LC_NUMERIC -->
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<!-- @itemx LC_TIME -->
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<dt><samp><span class="env">LC_ALL</span></samp><dd><a name="index-LANG-2837"></a><a name="index-LC_005fCTYPE-2838"></a><!-- @findex LC_COLLATE -->
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<a name="index-LC_005fMESSAGES-2839"></a><!-- @findex LC_MONETARY -->
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<!-- @findex LC_NUMERIC -->
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<!-- @findex LC_TIME -->
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<a name="index-LC_005fALL-2840"></a><a name="index-locale-2841"></a>These environment variables control the way that GCC uses
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localization information which allows GCC to work with different
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national conventions. GCC inspects the locale categories
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<samp><span class="env">LC_CTYPE</span></samp> and <samp><span class="env">LC_MESSAGES</span></samp> if it has been configured to do
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so. These locale categories can be set to any value supported by your
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installation. A typical value is ‘<samp><span class="samp">en_GB.UTF-8</span></samp>’ for English in the United
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Kingdom encoded in UTF-8.
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<p>The <samp><span class="env">LC_CTYPE</span></samp> environment variable specifies character
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classification. GCC uses it to determine the character boundaries in
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a string; this is needed for some multibyte encodings that contain quote
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and escape characters that are otherwise interpreted as a string
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end or escape.
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<p>The <samp><span class="env">LC_MESSAGES</span></samp> environment variable specifies the language to
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use in diagnostic messages.
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<p>If the <samp><span class="env">LC_ALL</span></samp> environment variable is set, it overrides the value
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of <samp><span class="env">LC_CTYPE</span></samp> and <samp><span class="env">LC_MESSAGES</span></samp>; otherwise, <samp><span class="env">LC_CTYPE</span></samp>
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and <samp><span class="env">LC_MESSAGES</span></samp> default to the value of the <samp><span class="env">LANG</span></samp>
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environment variable. If none of these variables are set, GCC
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defaults to traditional C English behavior.
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<br><dt><samp><span class="env">TMPDIR</span></samp><dd><a name="index-TMPDIR-2842"></a>If <samp><span class="env">TMPDIR</span></samp> is set, it specifies the directory to use for temporary
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files. GCC uses temporary files to hold the output of one stage of
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compilation which is to be used as input to the next stage: for example,
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the output of the preprocessor, which is the input to the compiler
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proper.
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<br><dt><samp><span class="env">GCC_COMPARE_DEBUG</span></samp><dd><a name="index-GCC_005fCOMPARE_005fDEBUG-2843"></a>Setting <samp><span class="env">GCC_COMPARE_DEBUG</span></samp> is nearly equivalent to passing
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<samp><span class="option">-fcompare-debug</span></samp> to the compiler driver. See the documentation
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of this option for more details.
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<br><dt><samp><span class="env">GCC_EXEC_PREFIX</span></samp><dd><a name="index-GCC_005fEXEC_005fPREFIX-2844"></a>If <samp><span class="env">GCC_EXEC_PREFIX</span></samp> is set, it specifies a prefix to use in the
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names of the subprograms executed by the compiler. No slash is added
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when this prefix is combined with the name of a subprogram, but you can
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specify a prefix that ends with a slash if you wish.
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<p>If <samp><span class="env">GCC_EXEC_PREFIX</span></samp> is not set, GCC attempts to figure out
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an appropriate prefix to use based on the pathname it is invoked with.
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<p>If GCC cannot find the subprogram using the specified prefix, it
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tries looking in the usual places for the subprogram.
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<p>The default value of <samp><span class="env">GCC_EXEC_PREFIX</span></samp> is
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<samp><var>prefix</var><span class="file">/lib/gcc/</span></samp> where <var>prefix</var> is the prefix to
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the installed compiler. In many cases <var>prefix</var> is the value
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of <code>prefix</code> when you ran the <samp><span class="file">configure</span></samp> script.
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<p>Other prefixes specified with <samp><span class="option">-B</span></samp> take precedence over this prefix.
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<p>This prefix is also used for finding files such as <samp><span class="file">crt0.o</span></samp> that are
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used for linking.
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<p>In addition, the prefix is used in an unusual way in finding the
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directories to search for header files. For each of the standard
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directories whose name normally begins with ‘<samp><span class="samp">/usr/local/lib/gcc</span></samp>’
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(more precisely, with the value of <samp><span class="env">GCC_INCLUDE_DIR</span></samp>), GCC tries
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replacing that beginning with the specified prefix to produce an
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alternate directory name. Thus, with <samp><span class="option">-Bfoo/</span></samp>, GCC searches
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<samp><span class="file">foo/bar</span></samp> just before it searches the standard directory
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<samp><span class="file">/usr/local/lib/bar</span></samp>.
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If a standard directory begins with the configured
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<var>prefix</var> then the value of <var>prefix</var> is replaced by
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<samp><span class="env">GCC_EXEC_PREFIX</span></samp> when looking for header files.
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<br><dt><samp><span class="env">COMPILER_PATH</span></samp><dd><a name="index-COMPILER_005fPATH-2845"></a>The value of <samp><span class="env">COMPILER_PATH</span></samp> is a colon-separated list of
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directories, much like <samp><span class="env">PATH</span></samp>. GCC tries the directories thus
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specified when searching for subprograms, if it can't find the
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subprograms using <samp><span class="env">GCC_EXEC_PREFIX</span></samp>.
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<br><dt><samp><span class="env">LIBRARY_PATH</span></samp><dd><a name="index-LIBRARY_005fPATH-2846"></a>The value of <samp><span class="env">LIBRARY_PATH</span></samp> is a colon-separated list of
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directories, much like <samp><span class="env">PATH</span></samp>. When configured as a native compiler,
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GCC tries the directories thus specified when searching for special
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linker files, if it can't find them using <samp><span class="env">GCC_EXEC_PREFIX</span></samp>. Linking
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using GCC also uses these directories when searching for ordinary
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libraries for the <samp><span class="option">-l</span></samp> option (but directories specified with
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<samp><span class="option">-L</span></samp> come first).
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<br><dt><samp><span class="env">LANG</span></samp><dd><a name="index-LANG-2847"></a><a name="index-locale-definition-2848"></a>This variable is used to pass locale information to the compiler. One way in
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which this information is used is to determine the character set to be used
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when character literals, string literals and comments are parsed in C and C++.
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When the compiler is configured to allow multibyte characters,
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the following values for <samp><span class="env">LANG</span></samp> are recognized:
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<dl>
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<dt>‘<samp><span class="samp">C-JIS</span></samp>’<dd>Recognize JIS characters.
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<br><dt>‘<samp><span class="samp">C-SJIS</span></samp>’<dd>Recognize SJIS characters.
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<br><dt>‘<samp><span class="samp">C-EUCJP</span></samp>’<dd>Recognize EUCJP characters.
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</dl>
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<p>If <samp><span class="env">LANG</span></samp> is not defined, or if it has some other value, then the
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compiler uses <code>mblen</code> and <code>mbtowc</code> as defined by the default locale to
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recognize and translate multibyte characters.
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</dl>
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<p class="noindent">Some additional environment variables affect the behavior of the
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preprocessor.
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<!-- Copyright (C) 1999-2015 Free Software Foundation, Inc. -->
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<!-- This is part of the CPP and GCC manuals. -->
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<!-- For copying conditions, see the file gcc.texi. -->
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<!-- -->
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<!-- Environment variables affecting the preprocessor -->
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<!-- -->
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<!-- If this file is included with the flag ``cppmanual'' set, it is -->
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<!-- formatted for inclusion in the CPP manual; otherwise the main GCC manual. -->
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<dl>
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<dt><samp><span class="env">CPATH</span></samp><a name="index-CPATH-2849"></a><dt><samp><span class="env">C_INCLUDE_PATH</span></samp><a name="index-C_005fINCLUDE_005fPATH-2850"></a><dt><samp><span class="env">CPLUS_INCLUDE_PATH</span></samp><a name="index-CPLUS_005fINCLUDE_005fPATH-2851"></a><dt><samp><span class="env">OBJC_INCLUDE_PATH</span></samp><a name="index-OBJC_005fINCLUDE_005fPATH-2852"></a><dd><!-- Commented out until ObjC++ is part of GCC: -->
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<!-- @itemx OBJCPLUS_INCLUDE_PATH -->
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Each variable's value is a list of directories separated by a special
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character, much like <samp><span class="env">PATH</span></samp>, in which to look for header files.
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The special character, <code>PATH_SEPARATOR</code>, is target-dependent and
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determined at GCC build time. For Microsoft Windows-based targets it is a
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semicolon, and for almost all other targets it is a colon.
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<p><samp><span class="env">CPATH</span></samp> specifies a list of directories to be searched as if
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specified with <samp><span class="option">-I</span></samp>, but after any paths given with <samp><span class="option">-I</span></samp>
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options on the command line. This environment variable is used
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regardless of which language is being preprocessed.
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<p>The remaining environment variables apply only when preprocessing the
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particular language indicated. Each specifies a list of directories
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to be searched as if specified with <samp><span class="option">-isystem</span></samp>, but after any
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paths given with <samp><span class="option">-isystem</span></samp> options on the command line.
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<p>In all these variables, an empty element instructs the compiler to
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search its current working directory. Empty elements can appear at the
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beginning or end of a path. For instance, if the value of
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<samp><span class="env">CPATH</span></samp> is <code>:/special/include</code>, that has the same
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effect as ‘<samp><span class="samp">-I. -I/special/include<!-- /@w --></span></samp>’.
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<!-- man end -->
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<!-- man begin ENVIRONMENT -->
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<br><dt><samp><span class="env">DEPENDENCIES_OUTPUT</span></samp><a name="index-DEPENDENCIES_005fOUTPUT-2853"></a><dd><a name="index-dependencies-for-make-as-output-2854"></a>If this variable is set, its value specifies how to output
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dependencies for Make based on the non-system header files processed
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by the compiler. System header files are ignored in the dependency
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output.
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<p>The value of <samp><span class="env">DEPENDENCIES_OUTPUT</span></samp> can be just a file name, in
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which case the Make rules are written to that file, guessing the target
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name from the source file name. Or the value can have the form
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‘<samp><var>file</var> <var>target</var></samp>’, in which case the rules are written to
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file <var>file</var> using <var>target</var> as the target name.
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<p>In other words, this environment variable is equivalent to combining
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the options <samp><span class="option">-MM</span></samp> and <samp><span class="option">-MF</span></samp>
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(see <a href="Preprocessor-Options.html#Preprocessor-Options">Preprocessor Options</a>),
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with an optional <samp><span class="option">-MT</span></samp> switch too.
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<br><dt><samp><span class="env">SUNPRO_DEPENDENCIES</span></samp><a name="index-SUNPRO_005fDEPENDENCIES-2855"></a><dd><a name="index-dependencies-for-make-as-output-2856"></a>This variable is the same as <samp><span class="env">DEPENDENCIES_OUTPUT</span></samp> (see above),
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except that system header files are not ignored, so it implies
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<samp><span class="option">-M</span></samp> rather than <samp><span class="option">-MM</span></samp>. However, the dependence on the
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main input file is omitted.
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See <a href="Preprocessor-Options.html#Preprocessor-Options">Preprocessor Options</a>.
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</dl>
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<!-- man end -->
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</body></html>
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