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c++windowmutexhandle

How do I know if HANDLE object been initialized?

I'm programming in C++ for Windows, and I have a HANDLE object to a mutex defined as:

static HANDLE Instance_Mutex;

I want to check whether this HANDLE is initialized by a mutex object or not; i.e is the code:

Instance_Mutex = CreateMutex(NULL,FALSE,NULL);

already been called.

If it is just lock it, and if not, create the mutex on this HANDLE and then lock it. What is the appropriate way to do it then?

Does the HANDLE object have a specific value when it has not yet been created?

Solution

  • If HANDLE is a global, then it will be zero initialized (i.e. it will be nullptr).

    It would be superior style, however, to explicitly initialize it to nullptr.

    Incidentally nullptr is also what CreateMutex returns on failure. So this invariant (nullptr if the HANDLE isn't a mutex) will be maintained even then.