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129 lines
6.3 KiB
HTML
129 lines
6.3 KiB
HTML
4 years ago
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<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
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<html>
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<!-- Copyright (C) 1988-2018 Free Software Foundation, Inc.
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Permission is granted to copy, distribute and/or modify this document
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under the terms of the GNU Free Documentation License, Version 1.3 or
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any later version published by the Free Software Foundation; with the
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Invariant Sections being "Funding Free Software", the Front-Cover
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Texts being (a) (see below), and with the Back-Cover Texts being (b)
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(see below). A copy of the license is included in the section entitled
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"GNU Free Documentation License".
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(a) The FSF's Front-Cover Text is:
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A GNU Manual
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(b) The FSF's Back-Cover Text is:
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You have freedom to copy and modify this GNU Manual, like GNU
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software. Copies published by the Free Software Foundation raise
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funds for GNU development. -->
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<!-- Created by GNU Texinfo 6.4, http://www.gnu.org/software/texinfo/ -->
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<head>
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<title>Headers (GNU Compiler Collection (GCC) Internals)</title>
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<meta name="description" content="Headers (GNU Compiler Collection (GCC) Internals)">
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<meta name="keywords" content="Headers (GNU Compiler Collection (GCC) Internals)">
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<meta name="resource-type" content="document">
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<meta name="distribution" content="global">
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<meta name="Generator" content="makeinfo">
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<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
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<link href="index.html#Top" rel="start" title="Top">
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<link href="Option-Index.html#Option-Index" rel="index" title="Option Index">
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<link href="index.html#SEC_Contents" rel="contents" title="Table of Contents">
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<link href="gcc-Directory.html#gcc-Directory" rel="up" title="gcc Directory">
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<link href="Documentation.html#Documentation" rel="next" title="Documentation">
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<link href="Library-Files.html#Library-Files" rel="prev" title="Library Files">
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<style type="text/css">
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ul.no-bullet {list-style: none}
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-->
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</style>
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</head>
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<body lang="en">
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<a name="Headers"></a>
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<div class="header">
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<p>
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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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</div>
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<hr>
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<a name="Headers-Installed-by-GCC"></a>
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<h4 class="subsection">6.3.6 Headers Installed by GCC</h4>
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<p>In general, GCC expects the system C library to provide most of the
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headers to be used with it. However, GCC will fix those headers if
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necessary to make them work with GCC, and will install some headers
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required of freestanding implementations. These headers are installed
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in <samp><var>libsubdir</var>/include</samp>. Headers for non-C runtime
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libraries are also installed by GCC; these are not documented here.
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(FIXME: document them somewhere.)
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</p>
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<p>Several of the headers GCC installs are in the <samp>ginclude</samp>
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directory. These headers, <samp>iso646.h</samp>,
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<samp>stdarg.h</samp>, <samp>stdbool.h</samp>, and <samp>stddef.h</samp>,
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are installed in <samp><var>libsubdir</var>/include</samp>,
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unless the target Makefile fragment (see <a href="Target-Fragment.html#Target-Fragment">Target Fragment</a>)
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overrides this by setting <code>USER_H</code>.
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</p>
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<p>In addition to these headers and those generated by fixing system
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headers to work with GCC, some other headers may also be installed in
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<samp><var>libsubdir</var>/include</samp>. <samp>config.gcc</samp> may set
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<code>extra_headers</code>; this specifies additional headers under
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<samp>config</samp> to be installed on some systems.
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</p>
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<p>GCC installs its own version of <code><float.h></code>, from <samp>ginclude/float.h</samp>.
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This is done to cope with command-line options that change the
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representation of floating point numbers.
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</p>
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<p>GCC also installs its own version of <code><limits.h></code>; this is generated
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from <samp>glimits.h</samp>, together with <samp>limitx.h</samp> and
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<samp>limity.h</samp> if the system also has its own version of
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<code><limits.h></code>. (GCC provides its own header because it is
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required of ISO C freestanding implementations, but needs to include
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the system header from its own header as well because other standards
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such as POSIX specify additional values to be defined in
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<code><limits.h></code>.) The system’s <code><limits.h></code> header is used via
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<samp><var>libsubdir</var>/include/syslimits.h</samp>, which is copied from
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<samp>gsyslimits.h</samp> if it does not need fixing to work with GCC; if it
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needs fixing, <samp>syslimits.h</samp> is the fixed copy.
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</p>
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<p>GCC can also install <code><tgmath.h></code>. It will do this when
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<samp>config.gcc</samp> sets <code>use_gcc_tgmath</code> to <code>yes</code>.
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</p>
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<hr>
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<div class="header">
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<p>
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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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</div>
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</body>
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</html>
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