Keywords: ISO C++ , library

Use
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## Use

Typical usage of the last two constructs is demonstrated as follows:

    #include <ext/concurrence.h>

    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 < max;  ++i)
          {
    	_Safe_iterator_base* __old = __iter;
    	__iter = __iter-<_M_next;
    	__old-<_M_detach_single();
          }
    }

In this sample code, an anonymous namespace is used to keep the `__mutex` private to the compilation unit, and `__scoped_lock` 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.

Several exception classes are used to keep track of concurrence-related errors. These classes are: `__concurrence_lock_error`, `__concurrence_unlock_error`, `__concurrence_wait_error`, and `__concurrence_broadcast_error`.

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