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diff --git a/share/doc/cpp/System-Headers.html b/share/doc/cpp/System-Headers.html new file mode 100644 index 0000000..0af2f0c --- /dev/null +++ b/share/doc/cpp/System-Headers.html @@ -0,0 +1,115 @@ +<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd"> +<html> +<!-- Copyright (C) 1987-2023 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. A copy of +the license is included in the +section entitled "GNU Free Documentation License". + +This manual contains no Invariant Sections. The Front-Cover Texts are +(a) (see below), and the Back-Cover Texts are (b) (see below). + +(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 5.1, http://www.gnu.org/software/texinfo/ --> +<head> +<title>The C Preprocessor: System Headers</title> + +<meta name="description" content="The C Preprocessor: System Headers"> +<meta name="keywords" content="The C Preprocessor: System Headers"> +<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="Index-of-Directives.html#Index-of-Directives" rel="index" title="Index of Directives"> +<link href="index.html#SEC_Contents" rel="contents" title="Table of Contents"> +<link href="Header-Files.html#Header-Files" rel="up" title="Header Files"> +<link href="Macros.html#Macros" rel="next" title="Macros"> +<link href="Wrapper-Headers.html#Wrapper-Headers" rel="previous" title="Wrapper Headers"> +<style type="text/css"> +<!-- +a.summary-letter {text-decoration: none} +blockquote.smallquotation {font-size: smaller} +div.display {margin-left: 3.2em} +div.example {margin-left: 3.2em} +div.indentedblock {margin-left: 3.2em} +div.lisp {margin-left: 3.2em} +div.smalldisplay {margin-left: 3.2em} +div.smallexample {margin-left: 3.2em} +div.smallindentedblock {margin-left: 3.2em; font-size: smaller} +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.nocodebreak {white-space:nowrap} +span.nolinebreak {white-space:nowrap} +span.roman {font-family:serif; font-weight:normal} +span.sansserif {font-family:sans-serif; font-weight:normal} +ul.no-bullet {list-style: none} +--> +</style> + + +</head> + +<body lang="en" bgcolor="#FFFFFF" text="#000000" link="#0000FF" vlink="#800080" alink="#FF0000"> +<a name="System-Headers"></a> +<div class="header"> +<p> +Previous: <a href="Wrapper-Headers.html#Wrapper-Headers" accesskey="p" rel="previous">Wrapper Headers</a>, Up: <a href="Header-Files.html#Header-Files" accesskey="u" rel="up">Header Files</a> [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="Index-of-Directives.html#Index-of-Directives" title="Index" rel="index">Index</a>]</p> +</div> +<hr> +<a name="System-Headers-1"></a> +<h3 class="section">2.8 System Headers</h3> +<a name="index-system-header-files-1"></a> + +<p>The header files declaring interfaces to the operating system and +runtime libraries often cannot be written in strictly conforming C. +Therefore, GCC gives code found in <em>system headers</em> special +treatment. All warnings, other than those generated by ‘<samp>#warning</samp>’ +(see <a href="Diagnostics.html#Diagnostics">Diagnostics</a>), are suppressed while GCC is processing a system +header. Macros defined in a system header are immune to a few warnings +wherever they are expanded. This immunity is granted on an ad-hoc +basis, when we find that a warning generates lots of false positives +because of code in macros defined in system headers. +</p> +<p>Normally, only the headers found in specific directories are considered +system headers. These directories are determined when GCC is compiled. +There are, however, two ways to make normal headers into system headers: +</p> +<ul> +<li> Header files found in directories added to the search path with the +<samp>-isystem</samp> and <samp>-idirafter</samp> command-line options are +treated as system headers for the purposes of diagnostics. + +</li><li> <a name="index-_0023pragma-GCC-system_005fheader"></a> +There is also a directive, <code>#pragma GCC <span class="nolinebreak">system_header</span><!-- /@w --></code>, which +tells GCC to consider the rest of the current include file a system +header, no matter where it was found. Code that comes before the +‘<samp>#pragma</samp>’ in the file is not affected. <code>#pragma GCC <span class="nolinebreak">system_header</span><!-- /@w --></code> has no effect in the primary source file. +</li></ul> + +<p>On some targets, such as RS/6000 AIX, GCC implicitly surrounds all +system headers with an ‘<samp>extern "C"</samp>’ block when compiling as C++. +</p> + + + +</body> +</html> |