You cannot select more than 25 topics
Topics must start with a letter or number, can include dashes ('-') and can be up to 35 characters long.
112 lines
4.6 KiB
HTML
112 lines
4.6 KiB
HTML
4 years ago
|
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
|
||
|
|
<html>
|
||
|
|
<!-- Copyright (C) 1988-2018 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 6.4, http://www.gnu.org/software/texinfo/ -->
|
||
|
|
<head>
|
||
|
|
<title>Synchronization (Using the GNU Compiler Collection (GCC))</title>
|
||
|
|
|
||
|
|
<meta name="description" content="Synchronization (Using the GNU Compiler Collection (GCC))">
|
||
|
|
<meta name="keywords" content="Synchronization (Using the GNU Compiler Collection (GCC))">
|
||
|
|
<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="Option-Index.html#Option-Index" rel="index" title="Option Index">
|
||
|
|
<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="Fast-enumeration.html#Fast-enumeration" rel="next" title="Fast enumeration">
|
||
|
|
<link href="Exceptions.html#Exceptions" rel="prev" title="Exceptions">
|
||
|
|
<style type="text/css">
|
||
|
|
<!--
|
||
|
|
a.summary-letter {text-decoration: none}
|
||
|
|
blockquote.indentedblock {margin-right: 0em}
|
||
|
|
blockquote.smallindentedblock {margin-right: 0em; font-size: smaller}
|
||
|
|
blockquote.smallquotation {font-size: smaller}
|
||
|
|
div.display {margin-left: 3.2em}
|
||
|
|
div.example {margin-left: 3.2em}
|
||
|
|
div.lisp {margin-left: 3.2em}
|
||
|
|
div.smalldisplay {margin-left: 3.2em}
|
||
|
|
div.smallexample {margin-left: 3.2em}
|
||
|
|
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.nolinebreak {white-space: nowrap}
|
||
|
|
span.roman {font-family: initial; font-weight: normal}
|
||
|
|
span.sansserif {font-family: sans-serif; font-weight: normal}
|
||
|
|
ul.no-bullet {list-style: none}
|
||
|
|
-->
|
||
|
|
</style>
|
||
|
|
|
||
|
|
|
||
|
|
</head>
|
||
|
|
|
||
|
|
<body lang="en">
|
||
|
|
<a name="Synchronization"></a>
|
||
|
|
<div class="header">
|
||
|
|
<p>
|
||
|
|
Next: <a href="Fast-enumeration.html#Fast-enumeration" accesskey="n" rel="next">Fast enumeration</a>, Previous: <a href="Exceptions.html#Exceptions" accesskey="p" rel="prev">Exceptions</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="Option-Index.html#Option-Index" title="Index" rel="index">Index</a>]</p>
|
||
|
|
</div>
|
||
|
|
<hr>
|
||
|
|
<a name="Synchronization-1"></a>
|
||
|
|
<h3 class="section">8.8 Synchronization</h3>
|
||
|
|
|
||
|
|
<p>GNU Objective-C provides support for synchronized blocks:
|
||
|
|
</p>
|
||
|
|
<div class="smallexample">
|
||
|
|
<pre class="smallexample"> @synchronized (ObjCClass *guard) {
|
||
|
|
…
|
||
|
|
}
|
||
|
|
</pre></div>
|
||
|
|
|
||
|
|
<p>Upon entering the <code>@synchronized</code> block, a thread of execution
|
||
|
|
shall first check whether a lock has been placed on the corresponding
|
||
|
|
<code>guard</code> object by another thread. If it has, the current thread
|
||
|
|
shall wait until the other thread relinquishes its lock. Once
|
||
|
|
<code>guard</code> becomes available, the current thread will place its own
|
||
|
|
lock on it, execute the code contained in the <code>@synchronized</code>
|
||
|
|
block, and finally relinquish the lock (thereby making <code>guard</code>
|
||
|
|
available to other threads).
|
||
|
|
</p>
|
||
|
|
<p>Unlike Java, Objective-C does not allow for entire methods to be
|
||
|
|
marked <code>@synchronized</code>. Note that throwing exceptions out of
|
||
|
|
<code>@synchronized</code> blocks is allowed, and will cause the guarding
|
||
|
|
object to be unlocked properly.
|
||
|
|
</p>
|
||
|
|
<p>Because of the interactions between synchronization and exception
|
||
|
|
handling, you can only use <code>@synchronized</code> when compiling with
|
||
|
|
exceptions enabled, that is with the command line option
|
||
|
|
<samp>-fobjc-exceptions</samp>.
|
||
|
|
</p>
|
||
|
|
|
||
|
|
|
||
|
|
|
||
|
|
|
||
|
|
</body>
|
||
|
|
</html>
|