SDL_SemWaitTimeout man page

SDL_SemWaitTimeout — Lock a semaphore, but only wait up to a specified maximum time.


#include "SDL.h" #include "SDL_thread.h"

int SDL_SemWaitTimeout(SDL_sem *sem, Uint32 timeout);


SDL_SemWaitTimeout() is a varient of SDL_SemWait with a maximum timeout value. If the value of the semaphore pointed to by sem is positive (greater than zero) it will atomically decrement the semaphore value and return 0, otherwise it will wait up to timeout milliseconds trying to lock the semaphore. This function is to be avoided if possible since on some platforms it is implemented by polling the semaphore every millisecond in a busy loop.

After SDL_SemWaitTimeout() is successful, the semaphore can be released and its count atomically incremented by a successful call to SDL_SemPost.

Return Value

Returns 0 if the semaphore was successfully locked or either SDL_MUTEX_TIMEOUT or -1 if the timeout period was exceeded or there was an error, respectivly.

If the semaphore was not successfully locked, the semaphore will be unchanged.


res = SDL_SemWaitTimeout(my_sem, WAIT_TIMEOUT_MILLISEC);

if (res == SDL_MUTEX_TIMEOUT) {
        return TRY_AGAIN;
if (res == -1) {
        return WAIT_ERROR;



See Also

SDL_CreateSemaphore, SDL_DestroySemaphore, SDL_SemWait, SDL_SemTryWait, SDL_SemPost, SDL_SemValue


SDL SDL API Reference Tue 11 Sep 2001, 23:00