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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/Structures-unions-enumerations-and-bit_002dfields-implementation.html | |
https://developer.arm.com/downloads/-/arm-gnu-toolchain-downloads
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diff --git a/share/doc/gcc/Structures-unions-enumerations-and-bit_002dfields-implementation.html b/share/doc/gcc/Structures-unions-enumerations-and-bit_002dfields-implementation.html new file mode 100644 index 0000000..dc4e421 --- /dev/null +++ b/share/doc/gcc/Structures-unions-enumerations-and-bit_002dfields-implementation.html @@ -0,0 +1,149 @@ +<!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): Structures unions enumerations and bit-fields implementation</title> + +<meta name="description" content="Using the GNU Compiler Collection (GCC): Structures unions enumerations and bit-fields implementation"> +<meta name="keywords" content="Using the GNU Compiler Collection (GCC): Structures unions enumerations and bit-fields implementation"> +<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-Implementation.html#C-Implementation" rel="up" title="C Implementation"> +<link href="Qualifiers-implementation.html#Qualifiers-implementation" rel="next" title="Qualifiers implementation"> +<link href="Hints-implementation.html#Hints-implementation" rel="previous" title="Hints implementation"> +<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="Structures-unions-enumerations-and-bit_002dfields-implementation"></a> +<div class="header"> +<p> +Next: <a href="Qualifiers-implementation.html#Qualifiers-implementation" accesskey="n" rel="next">Qualifiers implementation</a>, Previous: <a href="Hints-implementation.html#Hints-implementation" accesskey="p" rel="previous">Hints implementation</a>, Up: <a href="C-Implementation.html#C-Implementation" accesskey="u" rel="up">C Implementation</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="Structures_002c-Unions_002c-Enumerations_002c-and-Bit_002dFields"></a> +<h3 class="section">4.9 Structures, Unions, Enumerations, and Bit-Fields</h3> + +<ul> +<li> <cite>A member of a union object is accessed using a member of a +different type (C90 6.3.2.3).</cite> + +<p>The relevant bytes of the representation of the object are treated as +an object of the type used for the access. See <a href="Optimize-Options.html#Type_002dpunning">Type-punning</a>. This +may be a trap representation. +</p> +</li><li> <cite>Whether a “plain” <code>int</code> bit-field is treated as a +<code>signed int</code> bit-field or as an <code>unsigned int</code> bit-field +(C90 6.5.2, C90 6.5.2.1, C99 and C11 6.7.2, C99 and C11 6.7.2.1).</cite> + +<a name="index-funsigned_002dbitfields-1"></a> +<p>By default it is treated as <code>signed int</code> but this may be changed +by the <samp>-funsigned-bitfields</samp> option. +</p> +</li><li> <cite>Allowable bit-field types other than <code>_Bool</code>, <code>signed int</code>, +and <code>unsigned int</code> (C99 and C11 6.7.2.1).</cite> + +<p>Other integer types, such as <code>long int</code>, and enumerated types are +permitted even in strictly conforming mode. +</p> +</li><li> <cite>Whether atomic types are permitted for bit-fields (C11 6.7.2.1).</cite> + +<p>Atomic types are not permitted for bit-fields. +</p> +</li><li> <cite>Whether a bit-field can straddle a storage-unit boundary (C90 +6.5.2.1, C99 and C11 6.7.2.1).</cite> + +<p>Determined by ABI. +</p> +</li><li> <cite>The order of allocation of bit-fields within a unit (C90 +6.5.2.1, C99 and C11 6.7.2.1).</cite> + +<p>Determined by ABI. +</p> +</li><li> <cite>The alignment of non-bit-field members of structures (C90 +6.5.2.1, C99 and C11 6.7.2.1).</cite> + +<p>Determined by ABI. +</p> +</li><li> <cite>The integer type compatible with each enumerated type (C90 +6.5.2.2, C99 and C11 6.7.2.2).</cite> + +<a name="index-fshort_002denums-1"></a> +<p>Normally, the type is <code>unsigned int</code> if there are no negative +values in the enumeration, otherwise <code>int</code>. If +<samp>-fshort-enums</samp> is specified, then if there are negative values +it is the first of <code>signed char</code>, <code>short</code> and <code>int</code> +that can represent all the values, otherwise it is the first of +<code>unsigned char</code>, <code>unsigned short</code> and <code>unsigned int</code> +that can represent all the values. +</p> +<p>On some targets, <samp>-fshort-enums</samp> is the default; this is +determined by the ABI. +</p> +</li></ul> + +<hr> +<div class="header"> +<p> +Next: <a href="Qualifiers-implementation.html#Qualifiers-implementation" accesskey="n" rel="next">Qualifiers implementation</a>, Previous: <a href="Hints-implementation.html#Hints-implementation" accesskey="p" rel="previous">Hints implementation</a>, Up: <a href="C-Implementation.html#C-Implementation" accesskey="u" rel="up">C Implementation</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> |