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diff --git a/share/doc/gcc/Constant-string-objects.html b/share/doc/gcc/Constant-string-objects.html new file mode 100644 index 0000000..f5c5f40 --- /dev/null +++ b/share/doc/gcc/Constant-string-objects.html @@ -0,0 +1,148 @@ +<!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). 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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): Constant string objects</title> + +<meta name="description" content="Using the GNU Compiler Collection (GCC): Constant string objects"> +<meta name="keywords" content="Using the GNU Compiler Collection (GCC): Constant string objects"> +<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="Objective_002dC.html#Objective_002dC" rel="up" title="Objective-C"> +<link href="compatibility_005falias.html#compatibility_005falias" rel="next" title="compatibility_alias"> +<link href="Garbage-Collection.html#Garbage-Collection" rel="previous" title="Garbage Collection"> +<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="Constant-string-objects"></a> +<div class="header"> +<p> +Next: <a href="compatibility_005falias.html#compatibility_005falias" accesskey="n" rel="next">compatibility_alias</a>, Previous: <a href="Garbage-Collection.html#Garbage-Collection" accesskey="p" rel="previous">Garbage Collection</a>, Up: <a href="Objective_002dC.html#Objective_002dC" accesskey="u" rel="up">Objective-C</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="Constant-String-Objects"></a> +<h3 class="section">8.5 Constant String Objects</h3> + +<p>GNU Objective-C provides constant string objects that are generated +directly by the compiler. You declare a constant string object by +prefixing a C constant string with the character ‘<samp>@</samp>’: +</p> +<div class="smallexample"> +<pre class="smallexample"> id myString = @"this is a constant string object"; +</pre></div> + +<p>The constant string objects are by default instances of the +<code>NXConstantString</code> class which is provided by the GNU Objective-C +runtime. To get the definition of this class you must include the +<samp>objc/NXConstStr.h</samp> header file. +</p> +<p>User defined libraries may want to implement their own constant string +class. To be able to support them, the GNU Objective-C compiler provides +a new command line options <samp>-fconstant-string-class=<var>class-name</var></samp>. +The provided class should adhere to a strict structure, the same +as <code>NXConstantString</code>’s structure: +</p> +<div class="smallexample"> +<pre class="smallexample"> +@interface MyConstantStringClass +{ + Class isa; + char *c_string; + unsigned int len; +} +@end + +</pre></div> + +<p><code>NXConstantString</code> inherits from <code>Object</code>; user class +libraries may choose to inherit the customized constant string class +from a different class than <code>Object</code>. There is no requirement in +the methods the constant string class has to implement, but the final +ivar layout of the class must be the compatible with the given +structure. +</p> +<p>When the compiler creates the statically allocated constant string +object, the <code>c_string</code> field will be filled by the compiler with +the string; the <code>length</code> field will be filled by the compiler with +the string length; the <code>isa</code> pointer will be filled with +<code>NULL</code> by the compiler, and it will later be fixed up automatically +at runtime by the GNU Objective-C runtime library to point to the class +which was set by the <samp>-fconstant-string-class</samp> option when the +object file is loaded (if you wonder how it works behind the scenes, the +name of the class to use, and the list of static objects to fixup, are +stored by the compiler in the object file in a place where the GNU +runtime library will find them at runtime). +</p> +<p>As a result, when a file is compiled with the +<samp>-fconstant-string-class</samp> option, all the constant string objects +will be instances of the class specified as argument to this option. It +is possible to have multiple compilation units referring to different +constant string classes, neither the compiler nor the linker impose any +restrictions in doing this. +</p> +<hr> +<div class="header"> +<p> +Next: <a href="compatibility_005falias.html#compatibility_005falias" accesskey="n" rel="next">compatibility_alias</a>, Previous: <a href="Garbage-Collection.html#Garbage-Collection" accesskey="p" rel="previous">Garbage Collection</a>, Up: <a href="Objective_002dC.html#Objective_002dC" accesskey="u" rel="up">Objective-C</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> |