SDL_SemWait man page

SDL_SemWait — Lock a semaphore and suspend the thread if the semaphore value is zero.


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

int SDL_SemWait(SDL_sem *sem);


SDL_SemWait() suspends the calling thread until either the semaphore pointed to by sem has a positive value, the call is interrupted by a signal or error. If the call is successful it will atomically decrement the semaphore value.

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

Return Value

Returns 0 if successful or -1 if there was an error (leaving the semaphore unchanged).


if (SDL_SemWait(my_sem) == -1) {
        return WAIT_FAILED;



See Also

SDL_CreateSemaphore, SDL_DestroySemaphore, SDL_SemTryWait, SDL_SemWaitTimeout, SDL_SemPost, SDL_SemValue


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