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From: simnav AT gmail DOT com
Newsgroups: comp.os.msdos.djgpp
Subject: SIGALRM and debugger
Date: Thu, 28 Jun 2007 09:33:01 -0700
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To: djgpp AT delorie DOT com
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Reply-To: djgpp AT delorie DOT com

I've set with settitimer a 50msec timer and I've installed a function
to handle SIGALRM that is correctly called every 50msec. Often a
problem occours: if I set a breakpoint in main code when I press F8 to
proceed to next instruction, software crash reporting a general
protection fault (SIGSEGV) in a location that's checked with gdb seems
to be invalid; there is no kind of problem if I don't set breakpoints.
Is this a known problem of djgpp or I did something wrong ?

Thank you.
Best regards.
Simone Navari.

Here is the code I've used (i put breakpoint if Hello printf).

#include <pc.h>
#include <stdio.h>
#include <sys/time.h>
#include <signal.h>

void f(int n)
{
  printf("+\n");
}

int main(void)
{
  void(*old)(int);

  struct itimerval timer;

  asm("sti");

  timer.it_interval.tv_sec=0;
  timer.it_interval.tv_usec=50000;
  timer.it_value.tv_sec=0;
  timer.it_value.tv_usec=2000;

  setitimer(ITIMER_REAL,&timer,NULL);

  old=signal(SIGALRM,f);

  while(1)
  {
    if(kbhit())
    {
      int c=getkey();
      if(c=='A')
      {
        printf("Hello\n");
      }
      if(c==0x0d)
      {
        break;
      }
    }
  }

  signal(SIGALRM,old);
}