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| author | alk3pInjection <webmaster@raspii.tech> | 2024-02-04 16:16:35 +0800 |
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| committer | alk3pInjection <webmaster@raspii.tech> | 2024-02-04 16:16:35 +0800 |
| commit | abdaadbcae30fe0c9a66c7516798279fdfd97750 (patch) | |
| tree | 00a54a6e25601e43876d03c1a4a12a749d4a914c /share/doc/cpp/System_002dspecific-Predefined-Macros.html | |
https://developer.arm.com/downloads/-/arm-gnu-toolchain-downloads
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diff --git a/share/doc/cpp/System_002dspecific-Predefined-Macros.html b/share/doc/cpp/System_002dspecific-Predefined-Macros.html new file mode 100644 index 0000000..98891f3 --- /dev/null +++ b/share/doc/cpp/System_002dspecific-Predefined-Macros.html @@ -0,0 +1,127 @@ +<!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-specific Predefined Macros</title> + +<meta name="description" content="The C Preprocessor: System-specific Predefined Macros"> +<meta name="keywords" content="The C Preprocessor: System-specific Predefined Macros"> +<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="Predefined-Macros.html#Predefined-Macros" rel="up" title="Predefined Macros"> +<link href="C_002b_002b-Named-Operators.html#C_002b_002b-Named-Operators" rel="next" title="C++ Named Operators"> +<link href="Common-Predefined-Macros.html#Common-Predefined-Macros" rel="previous" title="Common Predefined Macros"> +<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_002dspecific-Predefined-Macros"></a> +<div class="header"> +<p> +Next: <a href="C_002b_002b-Named-Operators.html#C_002b_002b-Named-Operators" accesskey="n" rel="next">C++ Named Operators</a>, Previous: <a href="Common-Predefined-Macros.html#Common-Predefined-Macros" accesskey="p" rel="previous">Common Predefined Macros</a>, Up: <a href="Predefined-Macros.html#Predefined-Macros" accesskey="u" rel="up">Predefined Macros</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_002dspecific-Predefined-Macros-1"></a> +<h4 class="subsection">3.7.3 System-specific Predefined Macros</h4> + +<a name="index-system_002dspecific-predefined-macros"></a> +<a name="index-predefined-macros_002c-system_002dspecific"></a> +<a name="index-reserved-namespace"></a> + +<p>The C preprocessor normally predefines several macros that indicate what +type of system and machine is in use. They are obviously different on +each target supported by GCC. This manual, being for all systems and +machines, cannot tell you what their names are, but you can use +<code>cpp -dM</code> to see them all. See <a href="Invocation.html#Invocation">Invocation</a>. All system-specific +predefined macros expand to a constant value, so you can test them with +either ‘<samp>#ifdef</samp>’ or ‘<samp>#if</samp>’. +</p> +<p>The C standard requires that all system-specific macros be part of the +<em>reserved namespace</em>. All names which begin with two underscores, +or an underscore and a capital letter, are reserved for the compiler and +library to use as they wish. However, historically system-specific +macros have had names with no special prefix; for instance, it is common +to find <code>unix</code> defined on Unix systems. For all such macros, GCC +provides a parallel macro with two underscores added at the beginning +and the end. If <code>unix</code> is defined, <code>__unix__</code> will be defined +too. There will never be more than two underscores; the parallel of +<code>_mips</code> is <code>__mips__</code>. +</p> +<p>When the <samp>-ansi</samp> option, or any <samp>-std</samp> option that +requests strict conformance, is given to the compiler, all the +system-specific predefined macros outside the reserved namespace are +suppressed. The parallel macros, inside the reserved namespace, remain +defined. +</p> +<p>We are slowly phasing out all predefined macros which are outside the +reserved namespace. You should never use them in new programs, and we +encourage you to correct older code to use the parallel macros whenever +you find it. We don’t recommend you use the system-specific macros that +are in the reserved namespace, either. It is better in the long run to +check specifically for features you need, using a tool such as +<code>autoconf</code>. +</p> +<hr> +<div class="header"> +<p> +Next: <a href="C_002b_002b-Named-Operators.html#C_002b_002b-Named-Operators" accesskey="n" rel="next">C++ Named Operators</a>, Previous: <a href="Common-Predefined-Macros.html#Common-Predefined-Macros" accesskey="p" rel="previous">Common Predefined Macros</a>, Up: <a href="Predefined-Macros.html#Predefined-Macros" accesskey="u" rel="up">Predefined Macros</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> + + + +</body> +</html> |