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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/Thread_002dLocal.html | |
https://developer.arm.com/downloads/-/arm-gnu-toolchain-downloads
Change-Id: I7303388733328cd98ab9aa3c30236db67f2e9e9c
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diff --git a/share/doc/gcc/Thread_002dLocal.html b/share/doc/gcc/Thread_002dLocal.html new file mode 100644 index 0000000..1fe180f --- /dev/null +++ b/share/doc/gcc/Thread_002dLocal.html @@ -0,0 +1,144 @@ +<!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): Thread-Local</title> + +<meta name="description" content="Using the GNU Compiler Collection (GCC): Thread-Local"> +<meta name="keywords" content="Using the GNU Compiler Collection (GCC): Thread-Local"> +<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="C99-Thread_002dLocal-Edits.html#C99-Thread_002dLocal-Edits" rel="next" title="C99 Thread-Local Edits"> +<link href="Unnamed-Fields.html#Unnamed-Fields" rel="previous" title="Unnamed Fields"> +<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="Thread_002dLocal"></a> +<div class="header"> +<p> +Next: <a href="Binary-constants.html#Binary-constants" accesskey="n" rel="next">Binary constants</a>, Previous: <a href="Unnamed-Fields.html#Unnamed-Fields" accesskey="p" rel="previous">Unnamed Fields</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="Thread_002dLocal-Storage"></a> +<h3 class="section">6.64 Thread-Local Storage</h3> +<a name="index-Thread_002dLocal-Storage"></a> +<a name="index-TLS"></a> +<a name="index-_005f_005fthread"></a> + +<p>Thread-local storage (<acronym>TLS</acronym>) is a mechanism by which variables +are allocated such that there is one instance of the variable per extant +thread. The runtime model GCC uses to implement this originates +in the IA-64 processor-specific ABI, but has since been migrated +to other processors as well. It requires significant support from +the linker (<code>ld</code>), dynamic linker (<code>ld.so</code>), and +system libraries (<samp>libc.so</samp> and <samp>libpthread.so</samp>), so it +is not available everywhere. +</p> +<p>At the user level, the extension is visible with a new storage +class keyword: <code>__thread</code>. For example: +</p> +<div class="smallexample"> +<pre class="smallexample">__thread int i; +extern __thread struct state s; +static __thread char *p; +</pre></div> + +<p>The <code>__thread</code> specifier may be used alone, with the <code>extern</code> +or <code>static</code> specifiers, but with no other storage class specifier. +When used with <code>extern</code> or <code>static</code>, <code>__thread</code> must appear +immediately after the other storage class specifier. +</p> +<p>The <code>__thread</code> specifier may be applied to any global, file-scoped +static, function-scoped static, or static data member of a class. It may +not be applied to block-scoped automatic or non-static data member. +</p> +<p>When the address-of operator is applied to a thread-local variable, it is +evaluated at run time and returns the address of the current thread’s +instance of that variable. An address so obtained may be used by any +thread. When a thread terminates, any pointers to thread-local variables +in that thread become invalid. +</p> +<p>No static initialization may refer to the address of a thread-local variable. +</p> +<p>In C++, if an initializer is present for a thread-local variable, it must +be a <var>constant-expression</var>, as defined in 5.19.2 of the ANSI/ISO C++ +standard. +</p> +<p>See <a href="https://www.akkadia.org/drepper/tls.pdf">ELF Handling For Thread-Local Storage</a> for a detailed explanation of +the four thread-local storage addressing models, and how the runtime +is expected to function. +</p> +<table class="menu" border="0" cellspacing="0"> +<tr><td align="left" valign="top">• <a href="C99-Thread_002dLocal-Edits.html#C99-Thread_002dLocal-Edits" accesskey="1">C99 Thread-Local Edits</a>:</td><td> </td><td align="left" valign="top"> +</td></tr> +<tr><td align="left" valign="top">• <a href="C_002b_002b98-Thread_002dLocal-Edits.html#C_002b_002b98-Thread_002dLocal-Edits" accesskey="2">C++98 Thread-Local Edits</a>:</td><td> </td><td align="left" valign="top"> +</td></tr> +</table> + +<hr> +<div class="header"> +<p> +Next: <a href="Binary-constants.html#Binary-constants" accesskey="n" rel="next">Binary constants</a>, Previous: <a href="Unnamed-Fields.html#Unnamed-Fields" accesskey="p" rel="previous">Unnamed Fields</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> |