Effect of SDL_ClearError() on SDL Function Return Values

No, calling SDL_ClearError() has absolutely no effect on the return values of SDL functions.

SDL uses two primary mechanisms to report errors:

Function Return Values: This is the primary way SDL functions signal success or failure.

• Functions returning pointers (like SDL_CreateWindow, SDL_CreateRenderer, SDL_LoadBMP) typically return nullptr on failure.
• Functions returning integers (like SDL_Init, SDL_SetRenderDrawColor, SDL_RenderFillRect) typically return 0 on success and a negative value on failure.

Error Message String: This is a secondary mechanism providing supplementary human-readable details about the last error that occurred on the current thread, accessible via SDL_GetError().

SDL_ClearError() exclusively affects the second mechanism. It resets the internal error message string for the current thread to an empty string ("").

It's crucial to understand this distinction for correct error handling:

• You should always check the return value of an SDL function first to determine if an operation succeeded or failed.
• Only if the return value indicates failure should you typically call SDL_GetError() to get more information about why it failed.
• Calling SDL_ClearError() might be done after you've logged or handled an error reported by SDL_GetError(), but it won't change the fact that the original function call failed (as indicated by its return value).

1#include <SDL.h>
2#include <iostream>
3#include <string>
4
5int main(int argc, char* argv[]) {
6  // Intentionally fail SDL_Init by asking for
7  // a non-existent subsystem
8  int initResult{SDL_Init(0xFFFFFFFF)}; 
9
10  std::cout << "Initial SDL_Init result: "
11            << initResult << '\n';
12
13  if (initResult < 0) {
14    std::cout << "Error before ClearError: "
15              << SDL_GetError() << '\n';
16
17    SDL_ClearError(); 
18    std::cout << "Error after ClearError: "
19              << "'" << SDL_GetError() << "'" << '\n';
20
21    // Try again (it will still fail for the same reason)
22    int initResult2{SDL_Init(0xFFFFFFFF)}; 
23    std::cout << "Second SDL_Init result: "
24              << initResult2 << '\n'; 
25    std::cout << "Error after second fail: "
26              << SDL_GetError() << '\n';
27  }
28
29  SDL_Quit(); // Safe to call even if Init failed partially
30  return 0;
31}

1Initial SDL_Init result: -1
2Error before ClearError: Requested subsystem not available
3Error after ClearError: ''
4Second SDL_Init result: -1
5Error after second fail: Requested subsystem not available

As you can see:

• SDL_Init returned 1 initially, indicating failure.
• SDL_ClearError() successfully cleared the error message.
• Calling SDL_Init again still resulted in failure (returned 1) because SDL_ClearError() didn't fix the underlying issue (requesting an invalid subsystem). The error message was then set again by the second failed call.

Always rely on function return values for success/failure status and use SDL_GetError() / SDL_ClearError() for managing the associated diagnostic message.