Crash owing to improperly releasing memory.

[jacobbethany]

Version/Branch of Dear ImGui:

Newest docking branch

Back-ends:

imgui_impl_sdl3.cpp

Compiler, OS:

Tested on both Windows 10 MSVC Community 2022 and CLion with Msys2/Mingw/Ucrt64

Full config/build information:

Irrelevant

Details:

SDL3 has updated its API. When querying for gamepads, the memory is now automatically freed by SDL. Calling SDL_Free on the memory returned results in undefined behavior (and for me crashes).

See the documentation:
https://wiki.libsdl.org/SDL3/SDL_GetGamepads

I suggest replacing SDL_Free with SDL_ClaimTemporaryMemory or allowing it to be freed automatically when the SDL context is destroyed. (Locally, I used SDL_ClaimTemporaryMemory, until a fix is made to the repository and things are working, again.)

See:
imgui_impl_sdl3 ->
ImGui_ImplSDL3_UpdateGamepads -->
SDL_free ( sdl_gamepads );

vs SDL_ClaimTemporaryMemory ( sdl_gamepads );

PS:
The memory returned is now const T* instead of T*, thus const SDL_JoystickID *sdl_gamepads should be used, instead to avoid compiler warnings.

PPS:
SDL_GetDisplays now returns "const SDL_DisplayID *" instead of "SDL_DisplayID."

PPPS:
I want to say that I really appreciate the time and effort that goes into working on ImGUI! Hopefully, this will prevent someone else from chasing this bug.

Screenshots/Video:

No response

Minimal, Complete and Verifiable Example code:

Not necessary.

[ocornut]

Hello,
The gamepad part have already been fixed in master today:
eb72b5a (#7807)
I merged to docking now and corrected the SDL_DisplayID change.
It's all due to SDL3 which is currently unstable and fast changing API, so I am surprised so many people are using it already.

[ocornut]

Thank you for reporting!

[jacobbethany]

You're welcome for the reporting! It's the least I can do, if I'm getting any benefit from the project. I'm sorry for not noticing that it had already been fixed in the master branch. I can imagine that it must be somewhat frustrating to keep everything updated with SDL3's changes, right now. I was hoping to help with that.

I actually have another issue that I'm looking into right now, but I'm holding off until I have more information about a potential cause/fix.