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 - 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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 - <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>
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