1<html lang="en"> 2<head> 3<title>Environment Variables - Using the GNU Compiler Collection (GCC)</title> 4<meta http-equiv="Content-Type" content="text/html"> 5<meta name="description" content="Using the GNU Compiler Collection (GCC)"> 6<meta name="generator" content="makeinfo 4.13"> 7<link title="Top" rel="start" href="index.html#Top"> 8<link rel="up" href="Invoking-GCC.html#Invoking-GCC" title="Invoking GCC"> 9<link rel="prev" href="Code-Gen-Options.html#Code-Gen-Options" title="Code Gen Options"> 10<link rel="next" href="Precompiled-Headers.html#Precompiled-Headers" title="Precompiled Headers"> 11<link href="http://www.gnu.org/software/texinfo/" rel="generator-home" title="Texinfo Homepage"> 12<!-- 13Copyright (C) 1988-2013 Free Software Foundation, Inc. 14 15Permission is granted to copy, distribute and/or modify this document 16under the terms of the GNU Free Documentation License, Version 1.3 or 17any later version published by the Free Software Foundation; with the 18Invariant Sections being ``Funding Free Software'', the Front-Cover 19Texts being (a) (see below), and with the Back-Cover Texts being (b) 20(see below). 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Some of them work by specifying directories or prefixes to use 62when searching for various kinds of files. Some are used to specify other 63aspects of the compilation environment. 64 65 <p>Note that you can also specify places to search using options such as 66<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 67take precedence over places specified using environment variables, which 68in turn take precedence over those specified by the configuration of GCC. 69See <a href="../gccint/Driver.html#Driver">Controlling the Compilation Driver <samp><span class="file">gcc</span></samp></a>. 70 71 <dl> 72<dt><samp><span class="env">LANG</span></samp><dt><samp><span class="env">LC_CTYPE</span></samp><dd><!-- @itemx LC_COLLATE --> 73<dt><samp><span class="env">LC_MESSAGES</span></samp><dd><!-- @itemx LC_MONETARY --> 74<!-- @itemx LC_NUMERIC --> 75<!-- @itemx LC_TIME --> 76<dt><samp><span class="env">LC_ALL</span></samp><dd><a name="index-LANG-2386"></a><a name="index-LC_005fCTYPE-2387"></a><!-- @findex LC_COLLATE --> 77<a name="index-LC_005fMESSAGES-2388"></a><!-- @findex LC_MONETARY --> 78<!-- @findex LC_NUMERIC --> 79<!-- @findex LC_TIME --> 80<a name="index-LC_005fALL-2389"></a><a name="index-locale-2390"></a>These environment variables control the way that GCC uses 81localization information which allows GCC to work with different 82national conventions. GCC inspects the locale categories 83<samp><span class="env">LC_CTYPE</span></samp> and <samp><span class="env">LC_MESSAGES</span></samp> if it has been configured to do 84so. These locale categories can be set to any value supported by your 85installation. A typical value is ‘<samp><span class="samp">en_GB.UTF-8</span></samp>’ for English in the United 86Kingdom encoded in UTF-8. 87 88 <p>The <samp><span class="env">LC_CTYPE</span></samp> environment variable specifies character 89classification. GCC uses it to determine the character boundaries in 90a string; this is needed for some multibyte encodings that contain quote 91and escape characters that are otherwise interpreted as a string 92end or escape. 93 94 <p>The <samp><span class="env">LC_MESSAGES</span></samp> environment variable specifies the language to 95use in diagnostic messages. 96 97 <p>If the <samp><span class="env">LC_ALL</span></samp> environment variable is set, it overrides the value 98of <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> 99and <samp><span class="env">LC_MESSAGES</span></samp> default to the value of the <samp><span class="env">LANG</span></samp> 100environment variable. If none of these variables are set, GCC 101defaults to traditional C English behavior. 102 103 <br><dt><samp><span class="env">TMPDIR</span></samp><dd><a name="index-TMPDIR-2391"></a>If <samp><span class="env">TMPDIR</span></samp> is set, it specifies the directory to use for temporary 104files. GCC uses temporary files to hold the output of one stage of 105compilation which is to be used as input to the next stage: for example, 106the output of the preprocessor, which is the input to the compiler 107proper. 108 109 <br><dt><samp><span class="env">GCC_COMPARE_DEBUG</span></samp><dd><a name="index-GCC_005fCOMPARE_005fDEBUG-2392"></a>Setting <samp><span class="env">GCC_COMPARE_DEBUG</span></samp> is nearly equivalent to passing 110<samp><span class="option">-fcompare-debug</span></samp> to the compiler driver. See the documentation 111of this option for more details. 112 113 <br><dt><samp><span class="env">GCC_EXEC_PREFIX</span></samp><dd><a name="index-GCC_005fEXEC_005fPREFIX-2393"></a>If <samp><span class="env">GCC_EXEC_PREFIX</span></samp> is set, it specifies a prefix to use in the 114names of the subprograms executed by the compiler. No slash is added 115when this prefix is combined with the name of a subprogram, but you can 116specify a prefix that ends with a slash if you wish. 117 118 <p>If <samp><span class="env">GCC_EXEC_PREFIX</span></samp> is not set, GCC attempts to figure out 119an appropriate prefix to use based on the pathname it is invoked with. 120 121 <p>If GCC cannot find the subprogram using the specified prefix, it 122tries looking in the usual places for the subprogram. 123 124 <p>The default value of <samp><span class="env">GCC_EXEC_PREFIX</span></samp> is 125<samp><var>prefix</var><span class="file">/lib/gcc/</span></samp> where <var>prefix</var> is the prefix to 126the installed compiler. In many cases <var>prefix</var> is the value 127of <code>prefix</code> when you ran the <samp><span class="file">configure</span></samp> script. 128 129 <p>Other prefixes specified with <samp><span class="option">-B</span></samp> take precedence over this prefix. 130 131 <p>This prefix is also used for finding files such as <samp><span class="file">crt0.o</span></samp> that are 132used for linking. 133 134 <p>In addition, the prefix is used in an unusual way in finding the 135directories to search for header files. For each of the standard 136directories whose name normally begins with ‘<samp><span class="samp">/usr/local/lib/gcc</span></samp>’ 137(more precisely, with the value of <samp><span class="env">GCC_INCLUDE_DIR</span></samp>), GCC tries 138replacing that beginning with the specified prefix to produce an 139alternate directory name. Thus, with <samp><span class="option">-Bfoo/</span></samp>, GCC searches 140<samp><span class="file">foo/bar</span></samp> just before it searches the standard directory 141<samp><span class="file">/usr/local/lib/bar</span></samp>. 142If a standard directory begins with the configured 143<var>prefix</var> then the value of <var>prefix</var> is replaced by 144<samp><span class="env">GCC_EXEC_PREFIX</span></samp> when looking for header files. 145 146 <br><dt><samp><span class="env">COMPILER_PATH</span></samp><dd><a name="index-COMPILER_005fPATH-2394"></a>The value of <samp><span class="env">COMPILER_PATH</span></samp> is a colon-separated list of 147directories, much like <samp><span class="env">PATH</span></samp>. GCC tries the directories thus 148specified when searching for subprograms, if it can't find the 149subprograms using <samp><span class="env">GCC_EXEC_PREFIX</span></samp>. 150 151 <br><dt><samp><span class="env">LIBRARY_PATH</span></samp><dd><a name="index-LIBRARY_005fPATH-2395"></a>The value of <samp><span class="env">LIBRARY_PATH</span></samp> is a colon-separated list of 152directories, much like <samp><span class="env">PATH</span></samp>. When configured as a native compiler, 153GCC tries the directories thus specified when searching for special 154linker files, if it can't find them using <samp><span class="env">GCC_EXEC_PREFIX</span></samp>. Linking 155using GCC also uses these directories when searching for ordinary 156libraries for the <samp><span class="option">-l</span></samp> option (but directories specified with 157<samp><span class="option">-L</span></samp> come first). 158 159 <br><dt><samp><span class="env">LANG</span></samp><dd><a name="index-LANG-2396"></a><a name="index-locale-definition-2397"></a>This variable is used to pass locale information to the compiler. One way in 160which this information is used is to determine the character set to be used 161when character literals, string literals and comments are parsed in C and C++. 162When the compiler is configured to allow multibyte characters, 163the following values for <samp><span class="env">LANG</span></samp> are recognized: 164 165 <dl> 166<dt>‘<samp><span class="samp">C-JIS</span></samp>’<dd>Recognize JIS characters. 167<br><dt>‘<samp><span class="samp">C-SJIS</span></samp>’<dd>Recognize SJIS characters. 168<br><dt>‘<samp><span class="samp">C-EUCJP</span></samp>’<dd>Recognize EUCJP characters. 169</dl> 170 171 <p>If <samp><span class="env">LANG</span></samp> is not defined, or if it has some other value, then the 172compiler uses <code>mblen</code> and <code>mbtowc</code> as defined by the default locale to 173recognize and translate multibyte characters. 174</dl> 175 176<p class="noindent">Some additional environment variables affect the behavior of the 177preprocessor. 178 179<!-- Copyright (C) 1999-2013 Free Software Foundation, Inc. --> 180<!-- This is part of the CPP and GCC manuals. --> 181<!-- For copying conditions, see the file gcc.texi. --> 182<!-- --> 183<!-- Environment variables affecting the preprocessor --> 184<!-- --> 185<!-- If this file is included with the flag ``cppmanual'' set, it is --> 186<!-- formatted for inclusion in the CPP manual; otherwise the main GCC manual. --> 187 <dl> 188<dt><samp><span class="env">CPATH</span></samp><a name="index-CPATH-2398"></a><dt><samp><span class="env">C_INCLUDE_PATH</span></samp><a name="index-C_005fINCLUDE_005fPATH-2399"></a><dt><samp><span class="env">CPLUS_INCLUDE_PATH</span></samp><a name="index-CPLUS_005fINCLUDE_005fPATH-2400"></a><dt><samp><span class="env">OBJC_INCLUDE_PATH</span></samp><a name="index-OBJC_005fINCLUDE_005fPATH-2401"></a><dd><!-- Commented out until ObjC++ is part of GCC: --> 189<!-- @itemx OBJCPLUS_INCLUDE_PATH --> 190Each variable's value is a list of directories separated by a special 191character, much like <samp><span class="env">PATH</span></samp>, in which to look for header files. 192The special character, <code>PATH_SEPARATOR</code>, is target-dependent and 193determined at GCC build time. For Microsoft Windows-based targets it is a 194semicolon, and for almost all other targets it is a colon. 195 196 <p><samp><span class="env">CPATH</span></samp> specifies a list of directories to be searched as if 197specified with <samp><span class="option">-I</span></samp>, but after any paths given with <samp><span class="option">-I</span></samp> 198options on the command line. This environment variable is used 199regardless of which language is being preprocessed. 200 201 <p>The remaining environment variables apply only when preprocessing the 202particular language indicated. Each specifies a list of directories 203to be searched as if specified with <samp><span class="option">-isystem</span></samp>, but after any 204paths given with <samp><span class="option">-isystem</span></samp> options on the command line. 205 206 <p>In all these variables, an empty element instructs the compiler to 207search its current working directory. Empty elements can appear at the 208beginning or end of a path. For instance, if the value of 209<samp><span class="env">CPATH</span></samp> is <code>:/special/include</code>, that has the same 210effect as ‘<samp><span class="samp">-I. -I/special/include<!-- /@w --></span></samp>’. 211 212 <!-- man end --> 213 <!-- man begin ENVIRONMENT --> 214 <br><dt><samp><span class="env">DEPENDENCIES_OUTPUT</span></samp><a name="index-DEPENDENCIES_005fOUTPUT-2402"></a><dd><a name="index-dependencies-for-make-as-output-2403"></a>If this variable is set, its value specifies how to output 215dependencies for Make based on the non-system header files processed 216by the compiler. System header files are ignored in the dependency 217output. 218 219 <p>The value of <samp><span class="env">DEPENDENCIES_OUTPUT</span></samp> can be just a file name, in 220which case the Make rules are written to that file, guessing the target 221name from the source file name. Or the value can have the form 222‘<samp><var>file</var> <var>target</var></samp>’, in which case the rules are written to 223file <var>file</var> using <var>target</var> as the target name. 224 225 <p>In other words, this environment variable is equivalent to combining 226the options <samp><span class="option">-MM</span></samp> and <samp><span class="option">-MF</span></samp> 227(see <a href="Preprocessor-Options.html#Preprocessor-Options">Preprocessor Options</a>), 228with an optional <samp><span class="option">-MT</span></samp> switch too. 229 230 <br><dt><samp><span class="env">SUNPRO_DEPENDENCIES</span></samp><a name="index-SUNPRO_005fDEPENDENCIES-2404"></a><dd><a name="index-dependencies-for-make-as-output-2405"></a>This variable is the same as <samp><span class="env">DEPENDENCIES_OUTPUT</span></samp> (see above), 231except that system header files are not ignored, so it implies 232<samp><span class="option">-M</span></samp> rather than <samp><span class="option">-MM</span></samp>. However, the dependence on the 233main input file is omitted. 234See <a href="Preprocessor-Options.html#Preprocessor-Options">Preprocessor Options</a>. 235</dl> 236 237<!-- man end --> 238 </body></html> 239 240