Purpose of SDL_Quit() in SDL2

The SDL_Init() function initializes specific SDL subsystems that your program requested (like video, audio, timers, etc.). When initializing these subsystems, SDL often allocates resources, sets up connections with the operating system's underlying APIs, and reserves memory.

SDL_Quit() is the counterpart to SDL_Init(). Its purpose is to cleanly shut down all the SDL subsystems that were initialized. This involves:

• Releasing any memory allocated by SDL itself.
• Closing handles or connections to operating system resources (like graphics contexts or audio devices).
• Restoring any system settings that SDL might have changed temporarily.

Think of it like managing dynamic memory: if SDL_Init() is conceptually similar to using new to acquire resources, SDL_Quit() is like using delete to release them.

1int main(int argc, char** argv) {
2  // Initialize SDL subsystems (acquire resources)
3  if (SDL_Init(SDL_INIT_VIDEO | SDL_INIT_AUDIO) < 0) {
4    // Handle initialization error
5    return 1;
6  }
7
8  // ... create windows, render, play audio ...
9
10  // Clean up all initialized SDL subsystems
11  SDL_Quit();
12
13  return 0;
14}

Consequences of Forgetting SDL_Quit()

Forgetting to call SDL_Quit() before your program exits means that the cleanup process is skipped. The potential consequences include:

1. Resource Leaks: Memory allocated by SDL subsystems might not be freed. System handles (like file descriptors or graphics contexts) might remain open unnecessarily. While modern operating systems are quite good at reclaiming resources from terminated processes, relying on this is bad practice and can sometimes lead to issues, especially if the program opens and closes frequently or interacts with limited system resources.
2. Improper Hardware State: Subsystems might not be shut down correctly. For example, an audio device might be left in an unexpected state, or display settings might not be restored.
3. Incomplete Shutdown: Related libraries or drivers that SDL interacted with might not be notified that the application is closing, potentially causing instability or issues for other applications.

While a simple program might appear to terminate correctly without SDL_Quit(), omitting it is poor practice and can lead to subtle bugs, performance degradation over time, or instability, especially in larger applications or on different operating systems. Always pair SDL_Init() with a corresponding SDL_Quit() just before your program terminates.