libstdc++-v3/doc/html/manual/bk01pt03ch28s03.html


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<html xmlns="http://www.w3.org/1999/xhtml"><head><title>Use</title><meta name="generator" content="DocBook XSL-NS Stylesheets V1.76.1"/><meta name="keywords" content="&#10;      ISO C++&#10;    , &#10;      library&#10;    "/><meta name="keywords" content="&#10;      ISO C++&#10;    , &#10;      library&#10;    "/><link rel="home" href="../spine.html" title="The GNU C++ Library"/><link rel="up" href="ext_concurrency.html" title="Chapter 28. Concurrency"/><link rel="prev" href="bk01pt03ch28s02.html" title="Implementation"/><link rel="next" href="bk01pt04.html" title="Part IV.  Appendices"/></head><body><div class="navheader"><table width="100%" summary="Navigation header"><tr><th colspan="3" align="center">Use</th></tr><tr><td align="left"><a accesskey="p" href="bk01pt03ch28s02.html">Prev</a> </td><th width="60%" align="center">Chapter 28. Concurrency</th><td align="right"> <a accesskey="n" href="bk01pt04.html">Next</a></td></tr></table><hr/></div><div class="section" title="Use"><div class="titlepage"><div><div><h2 class="title"><a id="manual.ext.concurrency.use"/>Use</h2></div></div></div><p>Typical usage of the last two constructs is demonstrated as follows:
</p><pre class="programlisting">
#include &lt;ext/concurrence.h&gt;

namespace
{
  __gnu_cxx::__mutex safe_base_mutex;
} // anonymous namespace

namespace other
{
  void
  foo()
  {
    __gnu_cxx::__scoped_lock sentry(safe_base_mutex);
    for (int i = 0; i &lt; max;  ++i)
      {
	_Safe_iterator_base* __old = __iter;
	__iter = __iter-&lt;_M_next;
	__old-&lt;_M_detach_single();
      }
}
</pre><p>In this sample code, an anonymous namespace is used to keep
the <code class="code">__mutex</code> private to the compilation unit,
and <code class="code">__scoped_lock</code> is used to guard access to the critical
section within the for loop, locking the mutex on creation and freeing
the mutex as control moves out of this block.
</p><p>Several exception classes are used to keep track of
concurrence-related errors. These classes
are: <code class="code">__concurrence_lock_error</code>, <code class="code">__concurrence_unlock_error</code>, <code class="code">__concurrence_wait_error</code>,
and <code class="code">__concurrence_broadcast_error</code>.
</p></div><div class="navfooter"><hr/><table width="100%" summary="Navigation footer"><tr><td align="left"><a accesskey="p" href="bk01pt03ch28s02.html">Prev</a> </td><td align="center"><a accesskey="u" href="ext_concurrency.html">Up</a></td><td align="right"> <a accesskey="n" href="bk01pt04.html">Next</a></td></tr><tr><td align="left" valign="top">Implementation </td><td align="center"><a accesskey="h" href="../spine.html">Home</a></td><td align="right" valign="top"> Part IV. 
  Appendices
</td></tr></table></div></body></html>