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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/Conditional-Uses.html | |
https://developer.arm.com/downloads/-/arm-gnu-toolchain-downloads
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diff --git a/share/doc/cpp/Conditional-Uses.html b/share/doc/cpp/Conditional-Uses.html new file mode 100644 index 0000000..2d54537 --- /dev/null +++ b/share/doc/cpp/Conditional-Uses.html @@ -0,0 +1,110 @@ +<!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: Conditional Uses</title> + +<meta name="description" content="The C Preprocessor: Conditional Uses"> +<meta name="keywords" content="The C Preprocessor: Conditional Uses"> +<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="Conditionals.html#Conditionals" rel="up" title="Conditionals"> +<link href="Conditional-Syntax.html#Conditional-Syntax" rel="next" title="Conditional Syntax"> +<link href="Conditionals.html#Conditionals" rel="previous" title="Conditionals"> +<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="Conditional-Uses"></a> +<div class="header"> +<p> +Next: <a href="Conditional-Syntax.html#Conditional-Syntax" accesskey="n" rel="next">Conditional Syntax</a>, Up: <a href="Conditionals.html#Conditionals" accesskey="u" rel="up">Conditionals</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="Conditional-Uses-1"></a> +<h3 class="section">4.1 Conditional Uses</h3> + +<p>There are three general reasons to use a conditional. +</p> +<ul> +<li> A program may need to use different code depending on the machine or +operating system it is to run on. In some cases the code for one +operating system may be erroneous on another operating system; for +example, it might refer to data types or constants that do not exist on +the other system. When this happens, it is not enough to avoid +executing the invalid code. Its mere presence will cause the compiler +to reject the program. With a preprocessing conditional, the offending +code can be effectively excised from the program when it is not valid. + +</li><li> You may want to be able to compile the same source file into two +different programs. One version might make frequent time-consuming +consistency checks on its intermediate data, or print the values of +those data for debugging, and the other not. + +</li><li> A conditional whose condition is always false is one way to exclude code +from the program but keep it as a sort of comment for future reference. +</li></ul> + +<p>Simple programs that do not need system-specific logic or complex +debugging hooks generally will not need to use preprocessing +conditionals. +</p> + + + +</body> +</html> |