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<title>Directory Options - Using the GNU Compiler Collection (GCC)</title>
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<a name="Directory-Options"></a>
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Next: <a rel="next" accesskey="n" href="Spec-Files.html#Spec-Files">Spec Files</a>,
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Previous: <a rel="previous" accesskey="p" href="Link-Options.html#Link-Options">Link 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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<h3 class="section">3.14 Options for Directory Search</h3>
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<p><a name="index-directory-options-1243"></a><a name="index-options_002c-directory-search-1244"></a><a name="index-search-path-1245"></a>
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These options specify directories to search for header files, for
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libraries and for parts of the compiler:
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<dl>
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<dt><code>-I</code><var>dir</var><dd><a name="index-I-1246"></a>Add the directory <var>dir</var> to the head of the list of directories to be
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searched for header files. This can be used to override a system header
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file, substituting your own version, since these directories are
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searched before the system header file directories. However, you should
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not use this option to add directories that contain vendor-supplied
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system header files (use <samp><span class="option">-isystem</span></samp> for that). If you use more than
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one <samp><span class="option">-I</span></samp> option, the directories are scanned in left-to-right
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order; the standard system directories come after.
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<p>If a standard system include directory, or a directory specified with
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<samp><span class="option">-isystem</span></samp>, is also specified with <samp><span class="option">-I</span></samp>, the <samp><span class="option">-I</span></samp>
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option is ignored. The directory is still searched but as a
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system directory at its normal position in the system include chain.
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This is to ensure that GCC's procedure to fix buggy system headers and
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the ordering for the <code>include_next</code> directive are not inadvertently changed.
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If you really need to change the search order for system directories,
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use the <samp><span class="option">-nostdinc</span></samp> and/or <samp><span class="option">-isystem</span></samp> options.
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<br><dt><code>-iplugindir=</code><var>dir</var><dd><a name="index-iplugindir_003d-1247"></a>Set the directory to search for plugins that are passed
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by <samp><span class="option">-fplugin=</span><var>name</var></samp> instead of
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<samp><span class="option">-fplugin=</span><var>path</var><span class="option">/</span><var>name</var><span class="option">.so</span></samp>. This option is not meant
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to be used by the user, but only passed by the driver.
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<br><dt><code>-iquote</code><var>dir</var><dd><a name="index-iquote-1248"></a>Add the directory <var>dir</var> to the head of the list of directories to
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be searched for header files only for the case of <code>#include
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"</code><var>file</var><code>"</code>; they are not searched for <code>#include <</code><var>file</var><code>></code>,
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otherwise just like <samp><span class="option">-I</span></samp>.
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<br><dt><code>-L</code><var>dir</var><dd><a name="index-L-1249"></a>Add directory <var>dir</var> to the list of directories to be searched
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for <samp><span class="option">-l</span></samp>.
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<br><dt><code>-B</code><var>prefix</var><dd><a name="index-B-1250"></a>This option specifies where to find the executables, libraries,
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include files, and data files of the compiler itself.
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<p>The compiler driver program runs one or more of the subprograms
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<samp><span class="command">cpp</span></samp>, <samp><span class="command">cc1</span></samp>, <samp><span class="command">as</span></samp> and <samp><span class="command">ld</span></samp>. It tries
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<var>prefix</var> as a prefix for each program it tries to run, both with and
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without ‘<samp><var>machine</var><span class="samp">/</span><var>version</var><span class="samp">/</span></samp>’ (see <a href="Target-Options.html#Target-Options">Target Options</a>).
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<p>For each subprogram to be run, the compiler driver first tries the
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<samp><span class="option">-B</span></samp> prefix, if any. If that name is not found, or if <samp><span class="option">-B</span></samp>
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is not specified, the driver tries two standard prefixes,
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<samp><span class="file">/usr/lib/gcc/</span></samp> and <samp><span class="file">/usr/local/lib/gcc/</span></samp>. If neither of
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those results in a file name that is found, the unmodified program
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name is searched for using the directories specified in your
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<samp><span class="env">PATH</span></samp> environment variable.
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<p>The compiler checks to see if the path provided by <samp><span class="option">-B</span></samp>
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refers to a directory, and if necessary it adds a directory
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separator character at the end of the path.
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<p><samp><span class="option">-B</span></samp> prefixes that effectively specify directory names also apply
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to libraries in the linker, because the compiler translates these
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options into <samp><span class="option">-L</span></samp> options for the linker. They also apply to
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include files in the preprocessor, because the compiler translates these
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options into <samp><span class="option">-isystem</span></samp> options for the preprocessor. In this case,
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the compiler appends ‘<samp><span class="samp">include</span></samp>’ to the prefix.
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<p>The runtime support file <samp><span class="file">libgcc.a</span></samp> can also be searched for using
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the <samp><span class="option">-B</span></samp> prefix, if needed. If it is not found there, the two
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standard prefixes above are tried, and that is all. The file is left
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out of the link if it is not found by those means.
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<p>Another way to specify a prefix much like the <samp><span class="option">-B</span></samp> prefix is to use
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the environment variable <samp><span class="env">GCC_EXEC_PREFIX</span></samp>. See <a href="Environment-Variables.html#Environment-Variables">Environment Variables</a>.
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<p>As a special kludge, if the path provided by <samp><span class="option">-B</span></samp> is
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<samp><span class="file">[dir/]stage</span><var>N</var><span class="file">/</span></samp>, where <var>N</var> is a number in the range 0 to
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9, then it is replaced by <samp><span class="file">[dir/]include</span></samp>. This is to help
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with boot-strapping the compiler.
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<br><dt><code>-specs=</code><var>file</var><dd><a name="index-specs-1251"></a>Process <var>file</var> after the compiler reads in the standard <samp><span class="file">specs</span></samp>
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file, in order to override the defaults which the <samp><span class="command">gcc</span></samp> driver
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program uses when determining what switches to pass to <samp><span class="command">cc1</span></samp>,
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<samp><span class="command">cc1plus</span></samp>, <samp><span class="command">as</span></samp>, <samp><span class="command">ld</span></samp>, etc. More than one
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<samp><span class="option">-specs=</span><var>file</var></samp> can be specified on the command line, and they
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are processed in order, from left to right.
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<br><dt><code>--sysroot=</code><var>dir</var><dd><a name="index-sysroot-1252"></a>Use <var>dir</var> as the logical root directory for headers and libraries.
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For example, if the compiler normally searches for headers in
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<samp><span class="file">/usr/include</span></samp> and libraries in <samp><span class="file">/usr/lib</span></samp>, it instead
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searches <samp><var>dir</var><span class="file">/usr/include</span></samp> and <samp><var>dir</var><span class="file">/usr/lib</span></samp>.
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<p>If you use both this option and the <samp><span class="option">-isysroot</span></samp> option, then
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the <samp><span class="option">--sysroot</span></samp> option applies to libraries, but the
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<samp><span class="option">-isysroot</span></samp> option applies to header files.
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<p>The GNU linker (beginning with version 2.16) has the necessary support
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for this option. If your linker does not support this option, the
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header file aspect of <samp><span class="option">--sysroot</span></samp> still works, but the
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library aspect does not.
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<br><dt><code>--no-sysroot-suffix</code><dd><a name="index-no_002dsysroot_002dsuffix-1253"></a>For some targets, a suffix is added to the root directory specified
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with <samp><span class="option">--sysroot</span></samp>, depending on the other options used, so that
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headers may for example be found in
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<samp><var>dir</var><span class="file">/</span><var>suffix</var><span class="file">/usr/include</span></samp> instead of
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<samp><var>dir</var><span class="file">/usr/include</span></samp>. This option disables the addition of
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such a suffix.
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<br><dt><code>-I-</code><dd><a name="index-I_002d-1254"></a>This option has been deprecated. Please use <samp><span class="option">-iquote</span></samp> instead for
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<samp><span class="option">-I</span></samp> directories before the <samp><span class="option">-I-</span></samp> and remove the <samp><span class="option">-I-</span></samp>
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option.
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Any directories you specify with <samp><span class="option">-I</span></samp> options before the <samp><span class="option">-I-</span></samp>
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option are searched only for the case of <code>#include "</code><var>file</var><code>"</code>;
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they are not searched for <code>#include <</code><var>file</var><code>></code>.
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<p>If additional directories are specified with <samp><span class="option">-I</span></samp> options after
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the <samp><span class="option">-I-</span></samp> option, these directories are searched for all <code>#include</code>
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directives. (Ordinarily <em>all</em> <samp><span class="option">-I</span></samp> directories are used
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this way.)
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<p>In addition, the <samp><span class="option">-I-</span></samp> option inhibits the use of the current
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directory (where the current input file came from) as the first search
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directory for <code>#include "</code><var>file</var><code>"</code>. There is no way to
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override this effect of <samp><span class="option">-I-</span></samp>. With <samp><span class="option">-I.</span></samp> you can specify
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searching the directory that is current when the compiler is
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invoked. That is not exactly the same as what the preprocessor does
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by default, but it is often satisfactory.
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<p><samp><span class="option">-I-</span></samp> does not inhibit the use of the standard system directories
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for header files. Thus, <samp><span class="option">-I-</span></samp> and <samp><span class="option">-nostdinc</span></samp> are
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independent.
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</dl>
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