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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/The-preprocessing-language.html | |
https://developer.arm.com/downloads/-/arm-gnu-toolchain-downloads
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diff --git a/share/doc/cpp/The-preprocessing-language.html b/share/doc/cpp/The-preprocessing-language.html new file mode 100644 index 0000000..d372899 --- /dev/null +++ b/share/doc/cpp/The-preprocessing-language.html @@ -0,0 +1,154 @@ +<!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: The preprocessing language</title> + +<meta name="description" content="The C Preprocessor: The preprocessing language"> +<meta name="keywords" content="The C Preprocessor: The preprocessing language"> +<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="Overview.html#Overview" rel="up" title="Overview"> +<link href="Header-Files.html#Header-Files" rel="next" title="Header Files"> +<link href="Tokenization.html#Tokenization" rel="previous" title="Tokenization"> +<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="The-preprocessing-language"></a> +<div class="header"> +<p> +Previous: <a href="Tokenization.html#Tokenization" accesskey="p" rel="previous">Tokenization</a>, Up: <a href="Overview.html#Overview" accesskey="u" rel="up">Overview</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="The-preprocessing-language-1"></a> +<h3 class="section">1.4 The preprocessing language</h3> +<a name="index-directives"></a> +<a name="index-preprocessing-directives"></a> +<a name="index-directive-line"></a> +<a name="index-directive-name"></a> + +<p>After tokenization, the stream of tokens may simply be passed straight +to the compiler’s parser. However, if it contains any operations in the +<em>preprocessing language</em>, it will be transformed first. This stage +corresponds roughly to the standard’s “translation phase 4” and is +what most people think of as the preprocessor’s job. +</p> +<p>The preprocessing language consists of <em>directives</em> to be executed +and <em>macros</em> to be expanded. Its primary capabilities are: +</p> +<ul> +<li> Inclusion of header files. These are files of declarations that can be +substituted into your program. + +</li><li> Macro expansion. You can define <em>macros</em>, which are abbreviations +for arbitrary fragments of C code. The preprocessor will replace the +macros with their definitions throughout the program. Some macros are +automatically defined for you. + +</li><li> Conditional compilation. You can include or exclude parts of the +program according to various conditions. + +</li><li> Line control. If you use a program to combine or rearrange source files +into an intermediate file which is then compiled, you can use line +control to inform the compiler where each source line originally came +from. + +</li><li> Diagnostics. You can detect problems at compile time and issue errors +or warnings. +</li></ul> + +<p>There are a few more, less useful, features. +</p> +<p>Except for expansion of predefined macros, all these operations are +triggered with <em>preprocessing directives</em>. Preprocessing directives +are lines in your program that start with ‘<samp>#</samp>’. Whitespace is +allowed before and after the ‘<samp>#</samp>’. The ‘<samp>#</samp>’ is followed by an +identifier, the <em>directive name</em>. It specifies the operation to +perform. Directives are commonly referred to as ‘<samp>#<var>name</var></samp>’ +where <var>name</var> is the directive name. For example, ‘<samp>#define</samp>’ is +the directive that defines a macro. +</p> +<p>The ‘<samp>#</samp>’ which begins a directive cannot come from a macro +expansion. Also, the directive name is not macro expanded. Thus, if +<code>foo</code> is defined as a macro expanding to <code>define</code>, that does +not make ‘<samp>#foo</samp>’ a valid preprocessing directive. +</p> +<p>The set of valid directive names is fixed. Programs cannot define new +preprocessing directives. +</p> +<p>Some directives require arguments; these make up the rest of the +directive line and must be separated from the directive name by +whitespace. For example, ‘<samp>#define</samp>’ must be followed by a macro +name and the intended expansion of the macro. +</p> +<p>A preprocessing directive cannot cover more than one line. The line +may, however, be continued with backslash-newline, or by a block comment +which extends past the end of the line. In either case, when the +directive is processed, the continuations have already been merged with +the first line to make one long line. +</p> +<hr> +<div class="header"> +<p> +Previous: <a href="Tokenization.html#Tokenization" accesskey="p" rel="previous">Tokenization</a>, Up: <a href="Overview.html#Overview" accesskey="u" rel="up">Overview</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> |