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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/gcc/Statement-Attributes.html | |
https://developer.arm.com/downloads/-/arm-gnu-toolchain-downloads
Change-Id: I7303388733328cd98ab9aa3c30236db67f2e9e9c
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diff --git a/share/doc/gcc/Statement-Attributes.html b/share/doc/gcc/Statement-Attributes.html new file mode 100644 index 0000000..a4a441d --- /dev/null +++ b/share/doc/gcc/Statement-Attributes.html @@ -0,0 +1,154 @@ +<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd"> +<html> +<!-- This file documents the use of the GNU compilers. + +Copyright (C) 1988-2023 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; with the +Invariant Sections being "Funding Free Software", the Front-Cover +Texts being (a) (see below), and with the Back-Cover Texts being (b) +(see below). A copy of the license is included in the section entitled +"GNU Free Documentation License". + +(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>Using the GNU Compiler Collection (GCC): Statement Attributes</title> + +<meta name="description" content="Using the GNU Compiler Collection (GCC): Statement Attributes"> +<meta name="keywords" content="Using the GNU Compiler Collection (GCC): Statement Attributes"> +<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="Indices.html#Indices" rel="index" title="Indices"> +<link href="index.html#SEC_Contents" rel="contents" title="Table of Contents"> +<link href="C-Extensions.html#C-Extensions" rel="up" title="C Extensions"> +<link href="Attribute-Syntax.html#Attribute-Syntax" rel="next" title="Attribute Syntax"> +<link href="Enumerator-Attributes.html#Enumerator-Attributes" rel="previous" title="Enumerator Attributes"> +<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_US" bgcolor="#FFFFFF" text="#000000" link="#0000FF" vlink="#800080" alink="#FF0000"> +<a name="Statement-Attributes"></a> +<div class="header"> +<p> +Next: <a href="Attribute-Syntax.html#Attribute-Syntax" accesskey="n" rel="next">Attribute Syntax</a>, Previous: <a href="Enumerator-Attributes.html#Enumerator-Attributes" accesskey="p" rel="previous">Enumerator Attributes</a>, Up: <a href="C-Extensions.html#C-Extensions" accesskey="u" rel="up">C Extensions</a> [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="Indices.html#Indices" title="Index" rel="index">Index</a>]</p> +</div> +<hr> +<a name="Statement-Attributes-1"></a> +<h3 class="section">6.38 Statement Attributes</h3> +<a name="index-Statement-Attributes"></a> + +<p>GCC allows attributes to be set on null statements. See <a href="Attribute-Syntax.html#Attribute-Syntax">Attribute Syntax</a>, +for details of the exact syntax for using attributes. Other attributes are +available for functions (see <a href="Function-Attributes.html#Function-Attributes">Function Attributes</a>), variables +(see <a href="Variable-Attributes.html#Variable-Attributes">Variable Attributes</a>), labels (see <a href="Label-Attributes.html#Label-Attributes">Label Attributes</a>), enumerators +(see <a href="Enumerator-Attributes.html#Enumerator-Attributes">Enumerator Attributes</a>), and for types (see <a href="Type-Attributes.html#Type-Attributes">Type Attributes</a>). +</p> +<dl compact="compact"> +<dd><a name="index-fallthrough-statement-attribute"></a> +</dd> +<dt><code>fallthrough</code></dt> +<dd><p>The <code>fallthrough</code> attribute with a null statement serves as a +fallthrough statement. It hints to the compiler that a statement +that falls through to another case label, or user-defined label +in a switch statement is intentional and thus the +<samp>-Wimplicit-fallthrough</samp> warning must not trigger. The +fallthrough attribute may appear at most once in each attribute +list, and may not be mixed with other attributes. It can only +be used in a switch statement (the compiler will issue an error +otherwise), after a preceding statement and before a logically +succeeding case label, or user-defined label. +</p> +<p>This example uses the <code>fallthrough</code> statement attribute to indicate that +the <samp>-Wimplicit-fallthrough</samp> warning should not be emitted: +</p> +<div class="smallexample"> +<pre class="smallexample">switch (cond) + { + case 1: + bar (1); + __attribute__((fallthrough)); + case 2: + … + } +</pre></div> + +<a name="index-assume-statement-attribute"></a> +</dd> +<dt><code>assume</code></dt> +<dd><p>The <code>assume</code> attribute with a null statement serves as portable +assumption. It should have a single argument, a conditional expression, +which is not evaluated. If the argument would evaluate to true +at the point where it appears, it has no effect, otherwise there +is undefined behavior. This is a GNU variant of the ISO C++23 +standard <code>assume</code> attribute, but it can be used in any version of +both C and C++. +</p> +<div class="smallexample"> +<pre class="smallexample">int +foo (int x, int y) +{ + __attribute__((assume(x == 42))); + __attribute__((assume(++y == 43))); + return x + y; +} +</pre></div> + +<p><code>y</code> is not actually incremented and the compiler can but does not +have to optimize it to just <code>return 42 + 42;</code>. +</p> +</dd> +</dl> + +<hr> +<div class="header"> +<p> +Next: <a href="Attribute-Syntax.html#Attribute-Syntax" accesskey="n" rel="next">Attribute Syntax</a>, Previous: <a href="Enumerator-Attributes.html#Enumerator-Attributes" accesskey="p" rel="previous">Enumerator Attributes</a>, Up: <a href="C-Extensions.html#C-Extensions" accesskey="u" rel="up">C Extensions</a> [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="Indices.html#Indices" title="Index" rel="index">Index</a>]</p> +</div> + + + +</body> +</html> |