| <html lang="en"> |
| <head> |
| <title>Synchronization - Using the GNU Compiler Collection (GCC)</title> |
| <meta http-equiv="Content-Type" content="text/html"> |
| <meta name="description" content="Using the GNU Compiler Collection (GCC)"> |
| <meta name="generator" content="makeinfo 4.13"> |
| <link title="Top" rel="start" href="index.html#Top"> |
| <link rel="up" href="Objective_002dC.html#Objective_002dC" title="Objective-C"> |
| <link rel="prev" href="Exceptions.html#Exceptions" title="Exceptions"> |
| <link rel="next" href="Fast-enumeration.html#Fast-enumeration" title="Fast enumeration"> |
| <link href="http://www.gnu.org/software/texinfo/" rel="generator-home" title="Texinfo Homepage"> |
| <!-- |
| Copyright (C) 1988-2013 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.--> |
| <meta http-equiv="Content-Style-Type" content="text/css"> |
| <style type="text/css"><!-- |
| pre.display { font-family:inherit } |
| pre.format { font-family:inherit } |
| pre.smalldisplay { font-family:inherit; font-size:smaller } |
| pre.smallformat { font-family:inherit; font-size:smaller } |
| pre.smallexample { font-size:smaller } |
| pre.smalllisp { font-size:smaller } |
| span.sc { font-variant:small-caps } |
| span.roman { font-family:serif; font-weight:normal; } |
| span.sansserif { font-family:sans-serif; font-weight:normal; } |
| --></style> |
| </head> |
| <body> |
| <div class="node"> |
| <a name="Synchronization"></a> |
| <p> |
| Next: <a rel="next" accesskey="n" href="Fast-enumeration.html#Fast-enumeration">Fast enumeration</a>, |
| Previous: <a rel="previous" accesskey="p" href="Exceptions.html#Exceptions">Exceptions</a>, |
| Up: <a rel="up" accesskey="u" href="Objective_002dC.html#Objective_002dC">Objective-C</a> |
| <hr> |
| </div> |
| |
| <h3 class="section">8.8 Synchronization</h3> |
| |
| <p>GNU Objective-C provides support for synchronized blocks: |
| |
| <pre class="smallexample"> @synchronized (ObjCClass *guard) { |
| ... |
| } |
| </pre> |
| <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>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>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><span class="option">-fobjc-exceptions</span></samp>. |
| |
| <!-- ========================================================================= --> |
| </body></html> |
| |
