A structure used for thread-safe initialization and shutdown.
Defined in <SDL3/SDL_mutex.h>
typedef struct SDL_InitState
{
    SDL_AtomicInt status;
    SDL_ThreadID thread;
    void *reserved;
} SDL_InitState;Here is an example of using this:
   static SDL_InitState init;
   bool InitSystem(void)
   {
       if (!SDL_ShouldInit(&init)) {
           // The system is initialized
           return true;
       }
       // At this point, you should not leave this function without calling SDL_SetInitialized()
       bool initialized = DoInitTasks();
       SDL_SetInitialized(&init, initialized);
       return initialized;
   }
   bool UseSubsystem(void)
   {
       if (SDL_ShouldInit(&init)) {
           // Error, the subsystem isn't initialized
           SDL_SetInitialized(&init, false);
           return false;
       }
       // Do work using the initialized subsystem
       return true;
   }
   void QuitSystem(void)
   {
       if (!SDL_ShouldQuit(&init)) {
           // The system is not initialized
           return;
       }
       // At this point, you should not leave this function without calling SDL_SetInitialized()
       DoQuitTasks();
       SDL_SetInitialized(&init, false);
   }Note that this doesn't protect any resources created during initialization, or guarantee that nobody is using those resources during cleanup. You should use other mechanisms to protect those, if that's a concern for your code.
This struct is available since SDL 3.2.0.