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diff --git a/share/doc/cpp/Deleted-Code.html b/share/doc/cpp/Deleted-Code.html new file mode 100644 index 0000000..ad8a19f --- /dev/null +++ b/share/doc/cpp/Deleted-Code.html @@ -0,0 +1,109 @@ +<!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: Deleted Code</title> + +<meta name="description" content="The C Preprocessor: Deleted Code"> +<meta name="keywords" content="The C Preprocessor: Deleted Code"> +<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="Diagnostics.html#Diagnostics" rel="next" title="Diagnostics"> +<link href="_005f_005fhas_005finclude.html#g_t_005f_005fhas_005finclude" rel="previous" title="__has_include"> +<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="Deleted-Code"></a> +<div class="header"> +<p> +Previous: <a href="Conditional-Syntax.html#Conditional-Syntax" accesskey="p" rel="previous">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="Deleted-Code-1"></a> +<h3 class="section">4.3 Deleted Code</h3> +<a name="index-commenting-out-code"></a> + +<p>If you replace or delete a part of the program but want to keep the old +code around for future reference, you often cannot simply comment it +out. Block comments do not nest, so the first comment inside the old +code will end the commenting-out. The probable result is a flood of +syntax errors. +</p> +<p>One way to avoid this problem is to use an always-false conditional +instead. For instance, put <code>#if 0</code> before the deleted code and +<code>#endif</code> after it. This works even if the code being turned +off contains conditionals, but they must be entire conditionals +(balanced ‘<samp>#if</samp>’ and ‘<samp>#endif</samp>’). +</p> +<p>Some people use <code>#ifdef notdef</code> instead. This is risky, because +<code>notdef</code> might be accidentally defined as a macro, and then the +conditional would succeed. <code>#if 0</code> can be counted on to fail. +</p> +<p>Do not use <code>#if 0</code> for comments which are not C code. Use a real +comment, instead. The interior of <code>#if 0</code> must consist of complete +tokens; in particular, single-quote characters must balance. Comments +often contain unbalanced single-quote characters (known in English as +apostrophes). These confuse <code>#if 0</code>. They don’t confuse +‘<samp>/*</samp>’. +</p> + + + +</body> +</html> |