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330 lines
15 KiB
HTML
330 lines
15 KiB
HTML
4 years ago
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<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
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<html>
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<!-- Copyright (C) 1988-2018 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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Texts being (a) (see below), and with the Back-Cover Texts being (b)
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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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You have freedom to copy and modify this GNU Manual, like GNU
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software. Copies published by the Free Software Foundation raise
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funds for GNU development. -->
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<!-- Created by GNU Texinfo 6.4, http://www.gnu.org/software/texinfo/ -->
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<head>
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<title>Environment Variables (Using the GNU Compiler Collection (GCC))</title>
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<meta name="description" content="Environment Variables (Using the GNU Compiler Collection (GCC))">
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<meta name="keywords" content="Environment Variables (Using the GNU Compiler Collection (GCC))">
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<meta name="resource-type" content="document">
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<meta name="distribution" content="global">
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<meta name="Generator" content="makeinfo">
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<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
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<link href="index.html#Top" rel="start" title="Top">
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<link href="Option-Index.html#Option-Index" rel="index" title="Option Index">
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<link href="index.html#SEC_Contents" rel="contents" title="Table of Contents">
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<link href="Invoking-GCC.html#Invoking-GCC" rel="up" title="Invoking GCC">
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<link href="Precompiled-Headers.html#Precompiled-Headers" rel="next" title="Precompiled Headers">
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<link href="Spec-Files.html#Spec-Files" rel="prev" title="Spec Files">
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<style type="text/css">
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a.summary-letter {text-decoration: none}
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div.display {margin-left: 3.2em}
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div.example {margin-left: 3.2em}
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div.lisp {margin-left: 3.2em}
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kbd {font-style: oblique}
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pre.display {font-family: inherit}
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pre.format {font-family: inherit}
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pre.menu-comment {font-family: serif}
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pre.menu-preformatted {font-family: serif}
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pre.smalldisplay {font-family: inherit; font-size: smaller}
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pre.smallformat {font-family: inherit; font-size: smaller}
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pre.smalllisp {font-size: smaller}
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span.nolinebreak {white-space: nowrap}
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span.roman {font-family: initial; font-weight: normal}
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ul.no-bullet {list-style: none}
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-->
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</style>
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</head>
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<body lang="en">
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<a name="Environment-Variables"></a>
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<div class="header">
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<p>
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Next: <a href="Precompiled-Headers.html#Precompiled-Headers" accesskey="n" rel="next">Precompiled Headers</a>, Previous: <a href="Spec-Files.html#Spec-Files" accesskey="p" rel="prev">Spec Files</a>, Up: <a href="Invoking-GCC.html#Invoking-GCC" accesskey="u" rel="up">Invoking GCC</a> [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="Option-Index.html#Option-Index" title="Index" rel="index">Index</a>]</p>
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</div>
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<hr>
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<a name="Environment-Variables-Affecting-GCC"></a>
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<h3 class="section">3.20 Environment Variables Affecting GCC</h3>
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<a name="index-environment-variables"></a>
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<p>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>
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<p>Note that you can also specify places to search using options such as
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<samp>-B</samp>, <samp>-I</samp> and <samp>-L</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="http://gcc.gnu.org/onlinedocs/gccint/Driver.html#Driver">Controlling the Compilation Driver <samp>gcc</samp></a> in <cite>GNU Compiler Collection (GCC) Internals</cite>.
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</p>
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<dl compact="compact">
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<dt><code>LANG</code></dt>
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<dt><code>LC_CTYPE</code></dt>
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<dt><code>LC_MESSAGES</code></dt>
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<dt><code>LC_ALL</code></dt>
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<dd><a name="index-LANG"></a>
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<a name="index-LC_005fCTYPE"></a>
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<a name="index-LC_005fMESSAGES"></a>
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<a name="index-LC_005fALL"></a>
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<a name="index-locale"></a>
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<p>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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<code>LC_CTYPE</code> and <code>LC_MESSAGES</code> 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>en_GB.UTF-8</samp>’ for English in the United
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Kingdom encoded in UTF-8.
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</p>
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<p>The <code>LC_CTYPE</code> 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>
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<p>The <code>LC_MESSAGES</code> environment variable specifies the language to
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use in diagnostic messages.
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</p>
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<p>If the <code>LC_ALL</code> environment variable is set, it overrides the value
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of <code>LC_CTYPE</code> and <code>LC_MESSAGES</code>; otherwise, <code>LC_CTYPE</code>
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and <code>LC_MESSAGES</code> default to the value of the <code>LANG</code>
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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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</p>
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</dd>
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<dt><code>TMPDIR</code></dt>
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<dd><a name="index-TMPDIR"></a>
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<p>If <code>TMPDIR</code> 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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</p>
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</dd>
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<dt><code>GCC_COMPARE_DEBUG</code></dt>
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<dd><a name="index-GCC_005fCOMPARE_005fDEBUG"></a>
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<p>Setting <code>GCC_COMPARE_DEBUG</code> is nearly equivalent to passing
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<samp>-fcompare-debug</samp> to the compiler driver. See the documentation
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of this option for more details.
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</p>
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</dd>
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<dt><code>GCC_EXEC_PREFIX</code></dt>
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<dd><a name="index-GCC_005fEXEC_005fPREFIX"></a>
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<p>If <code>GCC_EXEC_PREFIX</code> 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>
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<p>If <code>GCC_EXEC_PREFIX</code> 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>
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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>
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<p>The default value of <code>GCC_EXEC_PREFIX</code> is
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<samp><var>prefix</var>/lib/gcc/</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>configure</samp> script.
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</p>
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<p>Other prefixes specified with <samp>-B</samp> take precedence over this prefix.
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</p>
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<p>This prefix is also used for finding files such as <samp>crt0.o</samp> that are
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used for linking.
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</p>
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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>/usr/local/lib/gcc</samp>’
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(more precisely, with the value of <code>GCC_INCLUDE_DIR</code>), 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>-Bfoo/</samp>, GCC searches
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<samp>foo/bar</samp> just before it searches the standard directory
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<samp>/usr/local/lib/bar</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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<code>GCC_EXEC_PREFIX</code> when looking for header files.
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</p>
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</dd>
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<dt><code>COMPILER_PATH</code></dt>
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<dd><a name="index-COMPILER_005fPATH"></a>
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<p>The value of <code>COMPILER_PATH</code> is a colon-separated list of
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directories, much like <code>PATH</code>. GCC tries the directories thus
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specified when searching for subprograms, if it cannot find the
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subprograms using <code>GCC_EXEC_PREFIX</code>.
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</p>
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</dd>
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<dt><code>LIBRARY_PATH</code></dt>
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<dd><a name="index-LIBRARY_005fPATH"></a>
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<p>The value of <code>LIBRARY_PATH</code> is a colon-separated list of
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directories, much like <code>PATH</code>. 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 cannot find them using <code>GCC_EXEC_PREFIX</code>. Linking
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using GCC also uses these directories when searching for ordinary
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libraries for the <samp>-l</samp> option (but directories specified with
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<samp>-L</samp> come first).
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</p>
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</dd>
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<dt><code>LANG</code></dt>
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<dd><a name="index-LANG-1"></a>
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<a name="index-locale-definition"></a>
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<p>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 <code>LANG</code> are recognized:
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</p>
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<dl compact="compact">
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<dt>‘<samp>C-JIS</samp>’</dt>
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<dd><p>Recognize JIS characters.
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</p></dd>
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<dt>‘<samp>C-SJIS</samp>’</dt>
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<dd><p>Recognize SJIS characters.
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</p></dd>
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<dt>‘<samp>C-EUCJP</samp>’</dt>
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<dd><p>Recognize EUCJP characters.
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</p></dd>
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</dl>
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<p>If <code>LANG</code> 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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</p></dd>
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</dl>
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<p>Some additional environment variables affect the behavior of the
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preprocessor.
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</p>
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<dl compact="compact">
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<dt><code>CPATH</code>
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<a name="index-CPATH"></a>
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</dt>
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<dt><code>C_INCLUDE_PATH</code>
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<a name="index-C_005fINCLUDE_005fPATH"></a>
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</dt>
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<dt><code>CPLUS_INCLUDE_PATH</code>
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<a name="index-CPLUS_005fINCLUDE_005fPATH"></a>
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</dt>
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<dt><code>OBJC_INCLUDE_PATH</code>
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<a name="index-OBJC_005fINCLUDE_005fPATH"></a>
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</dt>
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<dd><p>Each variable’s value is a list of directories separated by a special
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character, much like <code>PATH</code>, 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>
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<p><code>CPATH</code> specifies a list of directories to be searched as if
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specified with <samp>-I</samp>, but after any paths given with <samp>-I</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>
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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>-isystem</samp>, but after any
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paths given with <samp>-isystem</samp> options on the command line.
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</p>
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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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<code>CPATH</code> is <code>:/special/include</code>, that has the same
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effect as ‘<samp><span class="nolinebreak">-I.</span> <span class="nolinebreak">-I/special/include</span><!-- /@w --></samp>’.
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</p>
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</dd>
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<dt><code>DEPENDENCIES_OUTPUT</code>
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||
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<a name="index-DEPENDENCIES_005fOUTPUT"></a>
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|
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</dt>
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||
|
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<dd><a name="index-dependencies-for-make-as-output"></a>
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<p>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>
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<p>The value of <code>DEPENDENCIES_OUTPUT</code> 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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||
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</p>
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||
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<p>In other words, this environment variable is equivalent to combining
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the options <samp>-MM</samp> and <samp>-MF</samp>
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(see <a href="Preprocessor-Options.html#Preprocessor-Options">Preprocessor Options</a>),
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with an optional <samp>-MT</samp> switch too.
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</p>
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</dd>
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<dt><code>SUNPRO_DEPENDENCIES</code>
|
||
|
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<a name="index-SUNPRO_005fDEPENDENCIES"></a>
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</dt>
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<dd><a name="index-dependencies-for-make-as-output-1"></a>
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<p>This variable is the same as <code>DEPENDENCIES_OUTPUT</code> (see above),
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except that system header files are not ignored, so it implies
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<samp>-M</samp> rather than <samp>-MM</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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</p>
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</dd>
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<dt><code>SOURCE_DATE_EPOCH</code>
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<a name="index-SOURCE_005fDATE_005fEPOCH"></a>
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</dt>
|
||
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<dd><p>If this variable is set, its value specifies a UNIX timestamp to be
|
||
|
|
used in replacement of the current date and time in the <code>__DATE__</code>
|
||
|
|
and <code>__TIME__</code> macros, so that the embedded timestamps become
|
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|
|
reproducible.
|
||
|
|
</p>
|
||
|
|
<p>The value of <code>SOURCE_DATE_EPOCH</code> must be a UNIX timestamp,
|
||
|
|
defined as the number of seconds (excluding leap seconds) since
|
||
|
|
01 Jan 1970 00:00:00 represented in ASCII; identical to the output of
|
||
|
|
‘<samp><code>date +%s</code></samp>’ on GNU/Linux and other systems that support the
|
||
|
|
<code>%s</code> extension in the <code>date</code> command.
|
||
|
|
</p>
|
||
|
|
<p>The value should be a known timestamp such as the last modification
|
||
|
|
time of the source or package and it should be set by the build
|
||
|
|
process.
|
||
|
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</p>
|
||
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</dd>
|
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</dl>
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<hr>
|
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<div class="header">
|
||
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<p>
|
||
|
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Next: <a href="Precompiled-Headers.html#Precompiled-Headers" accesskey="n" rel="next">Precompiled Headers</a>, Previous: <a href="Spec-Files.html#Spec-Files" accesskey="p" rel="prev">Spec Files</a>, Up: <a href="Invoking-GCC.html#Invoking-GCC" accesskey="u" rel="up">Invoking GCC</a> [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="Option-Index.html#Option-Index" title="Index" rel="index">Index</a>]</p>
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</div>
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</body>
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</html>
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