====== (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_WaitThread =

Wait for a thread to finish.

== Syntax ==

<syntaxhighlight lang='c'>
void SDL_WaitThread(SDL_Thread * thread, int *status);
</syntaxhighlight>

== Function Parameters ==

{|
|'''thread'''
|the [[SDL_Thread]] pointer that was returned from the [[SDL_CreateThread]]() call that started this thread
|-
|'''status'''
|pointer to an integer that will receive the value returned from the thread function by its 'return', or NULL to not receive such value back.
|}

== Remarks ==

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
<code>status</code>, if <code>status</code> 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.

== Version ==

This function is available since SDL 3.0.0.

== Code Examples ==

<syntaxhighlight lang='c'>
#include "SDL.h"

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

    for (cnt = 0; cnt < 10; ++cnt) {
        SDL_Log("Thread counter: %d\n", cnt);
        SDL_Delay(50);
    }

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

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

    SDL_Log("Simple SDL_CreateThread test:");

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

    if (NULL == thread) {
        SDL_LogError(SDL_LOG_CATEGORY_APPLICATION, "SDL_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);
        SDL_Log("Thread returned value: %d\n", threadReturnValue);
    }

    return 0;
}
</syntaxhighlight>

== Related Functions ==

:[[SDL_CreateThread]]
:[[SDL_DetachThread]]

----
[[CategoryAPI]], [[CategoryThread]]