Add to an atomic variable.
int SDL_AtomicAdd(SDL_atomic_t *a, int v);
|a||a pointer to an SDL_atomic_t variable to be modified|
|v||the desired value to add|
Returns the previous value of the atomic variable.
This function also acts as a full memory barrier.
Note: If you don't know what this function is for, you shouldn't use it!
This function is available since SDL 2.0.2.