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Revision 16 as of 2013-11-14 06:32:19

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Use this function to wait for a thread to finish.


void SDL_WaitThread(SDL_Thread* thread,
                    int*        status)

Function Parameters


the SDL_Thread pointer that was returned from the SDL_CreateThread() call that started this thread


pointer to an integer that will receive the value returned from the thread function by its 'return', see Remarks for details

Code Examples

#include <stdio.h>
#include <SDL_thread.h>
#include <SDL_timer.h>

int TestThread(void *ptr);

int main(int argc, char *argv[])
    SDL_Thread *thread;
    int         threadReturnValue;

    printf("\nSimple SDL_CreateThread test:");

    // Simply create a thread
    thread = SDL_CreateThread(TestThread, "TestThread", (void *)NULL);

    if (NULL == thread) {
        printf("\nSDL_CreateThread failed: %s\n", SDL_GetError());
    } else {
        // Wait for the thread to complete. The thread functions return code will
        //       be placed in the "threadReturnValue" variable when it completes.
        SDL_WaitThread(thread, &threadReturnValue);
        printf("\nThread returned value:%d", threadReturnValue);

    return 1;

// Very simple thread - counts 0 to 9 delaying 50ms between increments
int TestThread(void *ptr)
    int        cnt;

    for (cnt = 0; cnt < 10; cnt++) {
        printf("\nThread counter: %d", cnt);

    // Return the final value to the SDL_WaitThread function above
    return cnt;


Wait for a thread to finish. Threads that haven't been detached will remain (as a "zombie") until this function cleans them up. Not doing so is a resource leak.

Once a thread has been cleaned up through this function, the SDL_Thread that references it becomes invalid and should not be referenced again. As such, only one thread may call SDL_WaitThread() on another.

The return code for the thread function is placed in the area pointed to by status, if status is not NULL.

You may not wait on a thread that has been used in a call to SDL_DetachThread(). Use either that function or this one, but not both, or behavior is undefined.

It is safe to pass a NULL thread to this function; it is a no-op.

Note that the thread pointer is freed by this function and is not valid afterward.

CategoryAPI, CategoryThread

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