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 <a name="Headers"></a>
 <div class="header">
 <p>
 Next: <a href="Documentation.html#Documentation" accesskey="n" rel="next">Documentation</a>, Previous: <a href="Library-Files.html#Library-Files" accesskey="p" rel="prev">Library Files</a>, Up: <a href="gcc-Directory.html#gcc-Directory" accesskey="u" rel="up">gcc Directory</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="Headers-Installed-by-GCC"></a>
 <h4 class="subsection">6.3.6 Headers Installed by GCC</h4>

 <p>In general, GCC expects the system C library to provide most of the
 headers to be used with it.  However, GCC will fix those headers if
 necessary to make them work with GCC, and will install some headers
 required of freestanding implementations.  These headers are installed
 in <samp><var>libsubdir</var>/include</samp>.  Headers for non-C runtime
 libraries are also installed by GCC; these are not documented here.
 (FIXME: document them somewhere.)
 </p>
 <p>Several of the headers GCC installs are in the <samp>ginclude</samp>
 directory.  These headers, <samp>iso646.h</samp>,
 <samp>stdarg.h</samp>, <samp>stdbool.h</samp>, and <samp>stddef.h</samp>,
 are installed in <samp><var>libsubdir</var>/include</samp>,
 unless the target Makefile fragment (see <a href="Target-Fragment.html#Target-Fragment">Target Fragment</a>)
 overrides this by setting <code>USER_H</code>.
 </p>
 <p>In addition to these headers and those generated by fixing system
 headers to work with GCC, some other headers may also be installed in
 <samp><var>libsubdir</var>/include</samp>.  <samp>config.gcc</samp> may set
 <code>extra_headers</code>; this specifies additional headers under
 <samp>config</samp> to be installed on some systems.
 </p>
 <p>GCC installs its own version of <code>&lt;float.h&gt;</code>, from <samp>ginclude/float.h</samp>.
 This is done to cope with command-line options that change the
 representation of floating point numbers.
 </p>
 <p>GCC also installs its own version of <code>&lt;limits.h&gt;</code>; this is generated
 from <samp>glimits.h</samp>, together with <samp>limitx.h</samp> and
 <samp>limity.h</samp> if the system also has its own version of
 <code>&lt;limits.h&gt;</code>.  (GCC provides its own header because it is
 required of ISO C freestanding implementations, but needs to include
 the system header from its own header as well because other standards
 such as POSIX specify additional values to be defined in
 <code>&lt;limits.h&gt;</code>.)  The system&rsquo;s <code>&lt;limits.h&gt;</code> header is used via
 <samp><var>libsubdir</var>/include/syslimits.h</samp>, which is copied from
 <samp>gsyslimits.h</samp> if it does not need fixing to work with GCC; if it
 needs fixing, <samp>syslimits.h</samp> is the fixed copy.
 </p>
 <p>GCC can also install <code>&lt;tgmath.h&gt;</code>.  It will do this when
 <samp>config.gcc</samp> sets <code>use_gcc_tgmath</code> to <code>yes</code>.
 </p>
 <hr>
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	<a name="Headers"></a>
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	<p>
	Next: <a href="Documentation.html#Documentation" accesskey="n" rel="next">Documentation</a>, Previous: <a href="Library-Files.html#Library-Files" accesskey="p" rel="prev">Library Files</a>, Up: <a href="gcc-Directory.html#gcc-Directory" accesskey="u" rel="up">gcc Directory</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>
	</div>
	<hr>
	<a name="Headers-Installed-by-GCC"></a>
	<h4 class="subsection">6.3.6 Headers Installed by GCC</h4>

	<p>In general, GCC expects the system C library to provide most of the
	headers to be used with it. However, GCC will fix those headers if
	necessary to make them work with GCC, and will install some headers
	required of freestanding implementations. These headers are installed
	in <samp><var>libsubdir</var>/include</samp>. Headers for non-C runtime
	libraries are also installed by GCC; these are not documented here.
	(FIXME: document them somewhere.)
	</p>
	<p>Several of the headers GCC installs are in the <samp>ginclude</samp>
	directory. These headers, <samp>iso646.h</samp>,
	<samp>stdarg.h</samp>, <samp>stdbool.h</samp>, and <samp>stddef.h</samp>,
	are installed in <samp><var>libsubdir</var>/include</samp>,
	unless the target Makefile fragment (see <a href="Target-Fragment.html#Target-Fragment">Target Fragment</a>)
	overrides this by setting <code>USER_H</code>.
	</p>
	<p>In addition to these headers and those generated by fixing system
	headers to work with GCC, some other headers may also be installed in
	<samp><var>libsubdir</var>/include</samp>. <samp>config.gcc</samp> may set
	<code>extra_headers</code>; this specifies additional headers under
	<samp>config</samp> to be installed on some systems.
	</p>
	<p>GCC installs its own version of <code><float.h></code>, from <samp>ginclude/float.h</samp>.
	This is done to cope with command-line options that change the
	representation of floating point numbers.
	</p>
	<p>GCC also installs its own version of <code><limits.h></code>; this is generated
	from <samp>glimits.h</samp>, together with <samp>limitx.h</samp> and
	<samp>limity.h</samp> if the system also has its own version of
	<code><limits.h></code>. (GCC provides its own header because it is
	required of ISO C freestanding implementations, but needs to include
	the system header from its own header as well because other standards
	such as POSIX specify additional values to be defined in
	<code><limits.h></code>.) The system’s <code><limits.h></code> header is used via
	<samp><var>libsubdir</var>/include/syslimits.h</samp>, which is copied from
	<samp>gsyslimits.h</samp> if it does not need fixing to work with GCC; if it
	needs fixing, <samp>syslimits.h</samp> is the fixed copy.
	</p>
	<p>GCC can also install <code><tgmath.h></code>. It will do this when
	<samp>config.gcc</samp> sets <code>use_gcc_tgmath</code> to <code>yes</code>.
	</p>
	<hr>
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	<p>
	Next: <a href="Documentation.html#Documentation" accesskey="n" rel="next">Documentation</a>, Previous: <a href="Library-Files.html#Library-Files" accesskey="p" rel="prev">Library Files</a>, Up: <a href="gcc-Directory.html#gcc-Directory" accesskey="u" rel="up">gcc Directory</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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