Tutorial :SDL/C++ OpenGL Program, how do I stop SDL from catching SIGINT



Question:

I am using SDL for an OpenGL application, running on Linux. My problem is that SDL is catching SIGINT and ignoring it. This is a pain because I am developing through a screen session, and I can't kill the running program with CTRL-C (the program the computer is running on is connected to a projector and has no input devices).

Is there a flag or something I can pass to SDL so that it does not capture SIGINT? I really just want the program to stop when it receives the signal (ie when I press ctrl-c).


Solution:1

Ctrl-C at the console generates an SDL_QUIT event. You can watch for this event using SDL_PollEvent or SDL_WaitEvent, and exit (cleanly) when it is detected.

Note that other actions can generate an SDL_QUIT event (e.g. attempting to close your main window via the window manager).


Solution:2

I have found an answer:

The SDL_INIT_NOPARACHUTE flag will capture fatal signals so that SDL can clean up after itself. It works for things like SIGSEGV, but apparently SIGINT is not fatal enough.

My solution is to reset the signal handler to SIGINT after SDL has been initialised:

SDL_Init(SDL_INIT_VIDEO | SDL_INIT_NOPARACHUTE);  signal(SIGINT, SIG_DFL);   

Thanks Cache for you input, it put me on the right track.

Michael


Solution:3

Passing the SDL_INIT_NOPARACHUTE initialisation flag to SDL_Init "Prevents SDL from catching fatal signals".


See: http://www.libsdl.org/cgi/docwiki.cgi/SDL_Init


Solution:4

If you're not actually using an event loop for some reason, you can use SDL_QuitRequested in your "poll stuff" loop.


Solution:5

In SDL_quit.c, there's a check for hints to determine whether the signal handlers should not be used in SDL_QuitInit(). Not sure if this existed in older versions when the original question was asked, but may be handy for those coming here fresh.

Just tested on my Windows application, I can now receive all signals properly again, using:

SDL_SetHint(SDL_HINT_NO_SIGNAL_HANDLERS, "1");  SDL_Init(...);  

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