Question

If I define a template struct like so:

template <typename T> 
struct SYNCHED_DATA
{
    SYNCHED_DATA()
    {
        hMutex = ::CreateMutex(NULL, FALSE, NULL);
    }
    ~SYNCHED_DATA()
    {
        if(hMutex)
            CloseHandle(hMutex);
        hMutex = NULL;
    }

    void set(T* pV)
    {
        if(pV)
        {
            ::WaitForSingleObject(hMutex, INFINITE);
            var = *pV;
            ::ReleaseMutex(hMutex);
        }
    }
    void get(T* pV)
    {
        if(pV)
        {
            ::WaitForSingleObject(hMutex, INFINITE);
            *pV = var;
            ::ReleaseMutex(hMutex);
        }
    }

private:
    HANDLE hMutex;
    T var;

    SYNCHED_DATA(const SYNCHED_DATA& s)
    {
    }
    SYNCHED_DATA& operator = (const SYNCHED_DATA& s)
    {
    }
};

Can I be assured that those WaitForSingleObject() APIs will always return WAIT_OBJECT_0? And if no, in what circumstances can they fail and how am I supposed to handle it then?

Answer 1

The Old New Thing has an article on how closing the handle before the wait succeeded will result in WAIT_ABANDONED for anybody waiting:

http://blogs.msdn.com/b/oldnewthing/archive/2005/09/12/463977.aspx

There is some discussion of WAIT_FAILED on this very site:

Why would WaitForSingleObject return WAIT_FAILED

These suggest that failure is a possibility even with an infinite timeout.