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    <p>In general mutexes can be used to control thread access across processes via a named mutex while critical sections are only for synchronizing thread access in the same process space.</p> <p>Neither of these classes truly get the benefit of RAII without wrapping them because in that case you would never need to explicitly call lock or unlock. Take for example this little bit of pseudo code using a boost mutex lock ...</p> <pre><code>void DoSomething() { // construction acquires lock on mutex boost::scoped_lock lock(&amp;aBoostMutex); // ... } // end scope - object is destroyed and lock is released </code></pre> <p>Now I'd argue you should avoid <code>CMutex</code>, <code>CCritalSection</code>, <code>CSemaphore</code>, and <code>CEvent</code> because the implementations are somewhat broken or at the very least inferior to other available libraries like boost. For example:</p> <ul> <li>Determining between a timeout from an abandoned mutex is impossible because the implementation checks return value only not the reason.</li> <li>No reentrant locks using <code>CSingleLock</code> so recursion will cause issues.</li> <li>Inability to have a named event between processes</li> </ul> <p>Depending on what you are tasked with you might have the opportunity to move away from the MFC wrappers on windows API and either implement your own atomic locks or use something like boost or C++0x features like <code>std::mutex</code> which not only are better implementations but provide cross-platform support.</p>
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    1. COUnfortunately, I'm stuck with MFC. My question was less about the difference between CMutex and CCriticalSection, and more about the difference between CSyncObject::Lock and CSingleLock::Lock. After doing some more research, it appears that CSingleLock behaves similarly to the boost::scoped_lock you show above (calls Unlock on destructor). I didn't realize CSingleLock prevented recursion, I assumed that each new instance on the stack would manage independently.
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    2. CO`CSyncObject` calls the Windows api `WaitForSingleObject` under the covers as far as I know and can't be used directly. It is the base class interface that `CMutex` derives from so it's used when you do `CMutex::Lock();` on your instance. `CSingleLock` is your `CCriticalSection` manipulator that is concrete and can be used as a scope lock with some wrapping. As mentioned before though there are some design problems with these objects so they should be avoided http://www.flounder.com/avoid_mfc_syncrhonization.htm
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