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<title>Using the GNU Compiler Collection (GCC): Directory Options</title>
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<a name="Directory-Options"></a>
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<p>
Next: <a href="Spec-Files.html#Spec-Files" accesskey="n" rel="next">Spec Files</a>, Previous: <a href="Link-Options.html#Link-Options" accesskey="p" rel="prev">Link Options</a>, Up: <a href="Invoking-GCC.html#Invoking-GCC" accesskey="u" rel="up">Invoking GCC</a> &nbsp; [<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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<hr>
<a name="Options-for-Directory-Search"></a>
<h3 class="section">3.14 Options for Directory Search</h3>
<a name="index-directory-options"></a>
<a name="index-options_002c-directory-search"></a>
<a name="index-search-path"></a>
<p>These options specify directories to search for header files, for
libraries and for parts of the compiler:
</p>
<dl compact="compact">
<dt><code>-I<var>dir</var></code></dt>
<dd><a name="index-I-1"></a>
<p>Add the directory <var>dir</var> to the head of the list of directories to be
searched for header files. This can be used to override a system header
file, substituting your own version, since these directories are
searched before the system header file directories. However, you should
not use this option to add directories that contain vendor-supplied
system header files (use <samp>-isystem</samp> for that). If you use more than
one <samp>-I</samp> option, the directories are scanned in left-to-right
order; the standard system directories come after.
</p>
<p>If a standard system include directory, or a directory specified with
<samp>-isystem</samp>, is also specified with <samp>-I</samp>, the <samp>-I</samp>
option is ignored. The directory is still searched but as a
system directory at its normal position in the system include chain.
This is to ensure that GCC&rsquo;s procedure to fix buggy system headers and
the ordering for the <code>include_next</code> directive are not inadvertently changed.
If you really need to change the search order for system directories,
use the <samp>-nostdinc</samp> and/or <samp>-isystem</samp> options.
</p>
</dd>
<dt><code>-iplugindir=<var>dir</var></code></dt>
<dd><a name="index-iplugindir_003d"></a>
<p>Set the directory to search for plugins that are passed
by <samp>-fplugin=<var>name</var></samp> instead of
<samp>-fplugin=<var>path</var>/<var>name</var>.so</samp>. This option is not meant
to be used by the user, but only passed by the driver.
</p>
</dd>
<dt><code>-iquote<var>dir</var></code></dt>
<dd><a name="index-iquote-1"></a>
<p>Add the directory <var>dir</var> to the head of the list of directories to
be searched for header files only for the case of <code>#include
&quot;<var>file</var>&quot;</code>; they are not searched for <code>#include &lt;<var>file</var>&gt;</code>,
otherwise just like <samp>-I</samp>.
</p>
</dd>
<dt><code>-L<var>dir</var></code></dt>
<dd><a name="index-L"></a>
<p>Add directory <var>dir</var> to the list of directories to be searched
for <samp>-l</samp>.
</p>
</dd>
<dt><code>-B<var>prefix</var></code></dt>
<dd><a name="index-B"></a>
<p>This option specifies where to find the executables, libraries,
include files, and data files of the compiler itself.
</p>
<p>The compiler driver program runs one or more of the subprograms
<code>cpp</code>, <code>cc1</code>, <code>as</code> and <code>ld</code>. It tries
<var>prefix</var> as a prefix for each program it tries to run, both with and
without &lsquo;<samp><var>machine</var>/<var>version</var>/</samp>&rsquo; (see <a href="Target-Options.html#Target-Options">Target Options</a>).
</p>
<p>For each subprogram to be run, the compiler driver first tries the
<samp>-B</samp> prefix, if any. If that name is not found, or if <samp>-B</samp>
is not specified, the driver tries two standard prefixes,
<samp>/usr/lib/gcc/</samp> and <samp>/usr/local/lib/gcc/</samp>. If neither of
those results in a file name that is found, the unmodified program
name is searched for using the directories specified in your
<code>PATH</code> environment variable.
</p>
<p>The compiler checks to see if the path provided by <samp>-B</samp>
refers to a directory, and if necessary it adds a directory
separator character at the end of the path.
</p>
<p><samp>-B</samp> prefixes that effectively specify directory names also apply
to libraries in the linker, because the compiler translates these
options into <samp>-L</samp> options for the linker. They also apply to
include files in the preprocessor, because the compiler translates these
options into <samp>-isystem</samp> options for the preprocessor. In this case,
the compiler appends &lsquo;<samp>include</samp>&rsquo; to the prefix.
</p>
<p>The runtime support file <samp>libgcc.a</samp> can also be searched for using
the <samp>-B</samp> prefix, if needed. If it is not found there, the two
standard prefixes above are tried, and that is all. The file is left
out of the link if it is not found by those means.
</p>
<p>Another way to specify a prefix much like the <samp>-B</samp> prefix is to use
the environment variable <code>GCC_EXEC_PREFIX</code>. See <a href="Environment-Variables.html#Environment-Variables">Environment Variables</a>.
</p>
<p>As a special kludge, if the path provided by <samp>-B</samp> is
<samp>[dir/]stage<var>N</var>/</samp>, where <var>N</var> is a number in the range 0 to
9, then it is replaced by <samp>[dir/]include</samp>. This is to help
with boot-strapping the compiler.
</p>
</dd>
<dt><code>-specs=<var>file</var></code></dt>
<dd><a name="index-specs"></a>
<p>Process <var>file</var> after the compiler reads in the standard <samp>specs</samp>
file, in order to override the defaults which the <code>gcc</code> driver
program uses when determining what switches to pass to <code>cc1</code>,
<code>cc1plus</code>, <code>as</code>, <code>ld</code>, etc. More than one
<samp>-specs=<var>file</var></samp> can be specified on the command line, and they
are processed in order, from left to right.
</p>
</dd>
<dt><code>--sysroot=<var>dir</var></code></dt>
<dd><a name="index-sysroot"></a>
<p>Use <var>dir</var> as the logical root directory for headers and libraries.
For example, if the compiler normally searches for headers in
<samp>/usr/include</samp> and libraries in <samp>/usr/lib</samp>, it instead
searches <samp><var>dir</var>/usr/include</samp> and <samp><var>dir</var>/usr/lib</samp>.
</p>
<p>If you use both this option and the <samp>-isysroot</samp> option, then
the <samp>--sysroot</samp> option applies to libraries, but the
<samp>-isysroot</samp> option applies to header files.
</p>
<p>The GNU linker (beginning with version 2.16) has the necessary support
for this option. If your linker does not support this option, the
header file aspect of <samp>--sysroot</samp> still works, but the
library aspect does not.
</p>
</dd>
<dt><code>--no-sysroot-suffix</code></dt>
<dd><a name="index-no_002dsysroot_002dsuffix"></a>
<p>For some targets, a suffix is added to the root directory specified
with <samp>--sysroot</samp>, depending on the other options used, so that
headers may for example be found in
<samp><var>dir</var>/<var>suffix</var>/usr/include</samp> instead of
<samp><var>dir</var>/usr/include</samp>. This option disables the addition of
such a suffix.
</p>
</dd>
<dt><code>-I-</code></dt>
<dd><a name="index-I_002d-1"></a>
<p>This option has been deprecated. Please use <samp>-iquote</samp> instead for
<samp>-I</samp> directories before the <samp>-I-</samp> and remove the <samp>-I-</samp>
option.
Any directories you specify with <samp>-I</samp> options before the <samp>-I-</samp>
option are searched only for the case of <code>#include &quot;<var>file</var>&quot;</code>;
they are not searched for <code>#include &lt;<var>file</var>&gt;</code>.
</p>
<p>If additional directories are specified with <samp>-I</samp> options after
the <samp>-I-</samp> option, these directories are searched for all <code>#include</code>
directives. (Ordinarily <em>all</em> <samp>-I</samp> directories are used
this way.)
</p>
<p>In addition, the <samp>-I-</samp> option inhibits the use of the current
directory (where the current input file came from) as the first search
directory for <code>#include &quot;<var>file</var>&quot;</code>. There is no way to
override this effect of <samp>-I-</samp>. With <samp>-I.</samp> you can specify
searching the directory that is current when the compiler is
invoked. That is not exactly the same as what the preprocessor does
by default, but it is often satisfactory.
</p>
<p><samp>-I-</samp> does not inhibit the use of the standard system directories
for header files. Thus, <samp>-I-</samp> and <samp>-nostdinc</samp> are
independent.
</p></dd>
</dl>
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