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<title>Apache Qpid : ScopedLocking</title>
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Apache Qpid : ScopedLocking
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This page last changed on Oct 19, 2006 by <font color="#0050B2">mmccorma</font>.
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<p>Always use scoped lockers to lock mutexes and the like. Don't do this:</p>
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<pre> lock.acquire();
do_stuff(); // DANGER: lock never released if exception thrown here.
lock.release();
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<p>Instead use a "scoped locker". This is simply a class that does the "acquire" in its constructor and the "release" in its destructor:</p>
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<pre> Locker locker(lock);
do_stuff();
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<p>Not only does this save a bit of typing, it guarantees that the lock will be released even if an exception is thrown, because C++ guarantees to call destructors of all local variables on exit from a scope. This also protects you forgetting to release the lock at every exit point from a function with multiple exit points - the compiler takes care of it for you. This technique applies more generally to any situation where you have to acquire and release resources. <tt>std::auto_ptr</tt> is a similar tool for memory management.</p>
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<td align="center"><font color="grey">Document generated by Confluence on Apr 22, 2008 02:47</font></td>
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