From: Shawn Hargreaves <Shawn AT talula DOT demon DOT co DOT uk>
Newsgroups: comp.os.msdos.djgpp
Subject: Re: Signal
Date: Sat, 4 Jan 1997 18:18:49 +0000
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To: djgpp AT delorie DOT com
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Andreas Vernersson writes:
>I've programmed a timer-interrupt (int 0x1c) and it works fine, but
>if i terminate my program with Ctrl-C when the timer is installed 
>the computer hung. I think this is caused because i dont't reinstall
>the old interrupt and my timer-interrupt is still there when the program
>tries to exit. So, how do i change the signal caused by Ctrl-C to 
>restore the real timer interrupt before exiting. Hm.. And hum..
>how do i make the usual "core dump" appear in the new signal before 
>exiting?

I'm not sure off the top of my head which signal it is that ctrl+C
generates, but in my Allegro startup code I install emergency shutdown
handlers for a range of signals, with the code:

   signal(SIGABRT, signal_handler);
   signal(SIGFPE,  signal_handler);
   signal(SIGILL,  signal_handler);
   signal(SIGSEGV, signal_handler);
   signal(SIGTERM, signal_handler);
   signal(SIGINT,  signal_handler);
   signal(SIGKILL, signal_handler);
   signal(SIGQUIT, signal_handler);

Within the signal handler itself, you can use raise() to chain to the
original handler, in order to get the usual register dump information.
My code is:

static void signal_handler(int num)
{
   static char msg[] = "Shutting down Allegro\r\n";

   allegro_exit();

   _write(STDERR_FILENO, msg, sizeof(msg)-1);

   signal(num, SIG_DFL);
   raise(num);
}

/*
 *  Shawn Hargreaves - shawn AT talula DOT demon DOT co DOT uk - http://www.talula.demon.co.uk/
 *  Ghoti: 'gh' as in 'enough', 'o' as in 'women', and 'ti' as in 'nation'.
 */