<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<!-- Copyright (C) 1988-2018 Free Software Foundation, Inc.
Permission is granted to copy, distribute and/or modify this document
under the terms of the GNU Free Documentation License, Version 1.3 or
any later version published by the Free Software Foundation; with the
Invariant Sections being "Funding Free Software", the Front-Cover
Texts being (a) (see below), and with the Back-Cover Texts being (b)
(see below). A copy of the license is included in the section entitled
"GNU Free Documentation License".
(a) The FSF's Front-Cover Text is:
A GNU Manual
(b) The FSF's Back-Cover Text is:
You have freedom to copy and modify this GNU Manual, like GNU
software. Copies published by the Free Software Foundation raise
funds for GNU development. -->
<!-- Created by GNU Texinfo 6.4, http://www.gnu.org/software/texinfo/ -->
<head>
<title>Fixed Headers (Using the GNU Compiler Collection (GCC))</title>
<meta name="description" content="Fixed Headers (Using the GNU Compiler Collection (GCC))">
<meta name="keywords" content="Fixed Headers (Using the GNU Compiler Collection (GCC))">
<meta name="resource-type" content="document">
<meta name="distribution" content="global">
<meta name="Generator" content="makeinfo">
<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
<link href="index.html#Top" rel="start" title="Top">
<link href="Option-Index.html#Option-Index" rel="index" title="Option Index">
<link href="index.html#SEC_Contents" rel="contents" title="Table of Contents">
<link href="Trouble.html#Trouble" rel="up" title="Trouble">
<link href="Standard-Libraries.html#Standard-Libraries" rel="next" title="Standard Libraries">
<link href="Incompatibilities.html#Incompatibilities" rel="prev" title="Incompatibilities">
<style type="text/css">
<!--
a.summary-letter {text-decoration: none}
blockquote.indentedblock {margin-right: 0em}
blockquote.smallindentedblock {margin-right: 0em; font-size: smaller}
blockquote.smallquotation {font-size: smaller}
div.display {margin-left: 3.2em}
div.example {margin-left: 3.2em}
div.lisp {margin-left: 3.2em}
div.smalldisplay {margin-left: 3.2em}
div.smallexample {margin-left: 3.2em}
div.smalllisp {margin-left: 3.2em}
kbd {font-style: oblique}
pre.display {font-family: inherit}
pre.format {font-family: inherit}
pre.menu-comment {font-family: serif}
pre.menu-preformatted {font-family: serif}
pre.smalldisplay {font-family: inherit; font-size: smaller}
pre.smallexample {font-size: smaller}
pre.smallformat {font-family: inherit; font-size: smaller}
pre.smalllisp {font-size: smaller}
span.nolinebreak {white-space: nowrap}
span.roman {font-family: initial; font-weight: normal}
span.sansserif {font-family: sans-serif; font-weight: normal}
ul.no-bullet {list-style: none}
-->
</style>
</head>
<body lang="en">
<a name="Fixed-Headers"></a>
<div class="header">
<p>
Next: <a href="Standard-Libraries.html#Standard-Libraries" accesskey="n" rel="next">Standard Libraries</a>, Previous: <a href="Incompatibilities.html#Incompatibilities" accesskey="p" rel="prev">Incompatibilities</a>, Up: <a href="Trouble.html#Trouble" accesskey="u" rel="up">Trouble</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="Fixed-Header-Files"></a>
<h3 class="section">13.4 Fixed Header Files</h3>
<p>GCC needs to install corrected versions of some system header files.
This is because most target systems have some header files that won’t
work with GCC unless they are changed. Some have bugs, some are
incompatible with ISO C, and some depend on special features of other
compilers.
</p>
<p>Installing GCC automatically creates and installs the fixed header
files, by running a program called <code>fixincludes</code>. Normally, you
don’t need to pay attention to this. But there are cases where it
doesn’t do the right thing automatically.
</p>
<ul>
<li> If you update the system’s header files, such as by installing a new
system version, the fixed header files of GCC are not automatically
updated. They can be updated using the <code>mkheaders</code> script
installed in
<samp><var>libexecdir</var>/gcc/<var>target</var>/<var>version</var>/install-tools/</samp>.
</li><li> On some systems, header file directories contain
machine-specific symbolic links in certain places. This makes it
possible to share most of the header files among hosts running the
same version of the system on different machine models.
<p>The programs that fix the header files do not understand this special
way of using symbolic links; therefore, the directory of fixed header
files is good only for the machine model used to build it.
</p>
<p>It is possible to make separate sets of fixed header files for the
different machine models, and arrange a structure of symbolic links so
as to use the proper set, but you’ll have to do this by hand.
</p></li></ul>
</body>
</html>