Question

For a certain project,I have to use the static mutex initializer in pthread.However my library is supposed to be portable on Windows as well.

pthread_mutex_t csapi_mutex = PTHREAD_MUTEX_INITIALIZER;

Is there a corrosponding static initializer on windows.?

Thanks.

Answer 1

I came up with this port of pthread-compatible mutex operations:

#define MUTEX_TYPE             HANDLE
#define MUTEX_INITIALIZER      NULL
#define MUTEX_SETUP(x)         (x) = CreateMutex(NULL, FALSE, NULL)
#define MUTEX_CLEANUP(x)       (CloseHandle(x) == 0)
#define MUTEX_LOCK(x)          emulate_pthread_mutex_lock(&(x))
#define MUTEX_UNLOCK(x)        (ReleaseMutex(x) == 0)

int emulate_pthread_mutex_lock(volatile MUTEX_TYPE *mx)
{ if (*mx == NULL) /* static initializer? */
  { HANDLE p = CreateMutex(NULL, FALSE, NULL);
    if (InterlockedCompareExchangePointer((PVOID*)mx, (PVOID)p, NULL) != NULL)
      CloseHandle(p);
  }
  return WaitForSingleObject(*mx, INFINITE) == WAIT_FAILED;
}

Basically, you want the initialization to happen atomically when the lock is used the first time. If two threads enter the if-body, then only one succeeds in initializing the lock. Note that there is no need to CloseHandle() for the static lock’s lifetime.