====== (This is the documentation for SDL3, which is under heavy development and the API is changing! [https://wiki.libsdl.org/SDL2/ SDL2] is the current stable version!) ====== = SDL_SemWait = Wait until a semaphore has a positive value and then decrements it. == Syntax == int SDL_SemWait(SDL_sem *sem); == Function Parameters == {| |'''sem''' |the semaphore wait on |} == Return Value == Returns 0 on success or a negative error code on failure; call [[SDL_GetError]]() for more information. == Remarks == This function suspends the calling thread until either the semaphore pointed to by sem has a positive value or the call is interrupted by a signal or error. If the call is successful it will atomically decrement the semaphore value. This function is the equivalent of calling [[SDL_SemWaitTimeout]]() with a time length of [[SDL_MUTEX_MAXWAIT]]. == Version == This function is available since SDL 3.0.0. == Code Examples == #define NB_WAITER 10 SDL_sem *sem; // Increments the semaphore every 2s int poster_thread() { for (int i = 0; i < NB_WAITER; i++) { SDL_SemPost(sem); SDL_Delay(2 * 1000); } return 0; } int waiter_thread() { int status; status = SDL_SemWait(sem); if (status == 0) { SDL_Log("Semaphore was decremented.\n"); } else { SDL_LogError(SDL_LOG_CATEGORY_APPLICATION, "An error has occured while waiting: %s\n", SDL_GetError()); } return 0; } int main() { sem = SDL_CreateSemaphore(0); create_and_wait_threads(); // 1 poster, 10 waiters SDL_DestroySemaphore(sem); } == Related Functions == :[[SDL_CreateSemaphore]] :[[SDL_DestroySemaphore]] :[[SDL_SemPost]] :[[SDL_SemTryWait]] :[[SDL_SemValue]] :[[SDL_SemWait]] :[[SDL_SemWaitTimeout]] ---- [[CategoryAPI]], [[CategoryMutex]]