From: caspard AT sci DOT kun DOT nl (Caspar Derksen)
Newsgroups: comp.os.msdos.djgpp
Subject: signal() and alarm() - Bug?
Date: 11 Mar 1997 18:35:13 +0100
Organization: University of Nijmegen, The Netherlands
Message-ID: <5g454h$lh0@hera.cs.kun.nl>
NNTP-Posting-Host: hera.cs.kun.nl
Lines: 60
To: djgpp AT delorie DOT com
DJ-Gateway: from newsgroup comp.os.msdos.djgpp

Hello,

I have the following problem: I want to perform some possibly expensive
computation that I want to abort if no result is found in time. I have
implemented this under Unix using alarm(). If some time limit is exceeded,
an alarm signal is raised that is handled by some procedure restoring
the previous state of the program.

With DJGPP, alarm() or signal() does not seem to work, although the
FAQ suggests that signals and alarm should work. I am using v2 under
Win95-DOS. Would v2.01 solve my problem? Does anyone known another
solution?

Thanks for reading,

Caspar Derksen

Example: under Unix this program prints "sigalrm!!\n" after one second.
Under DJGPP, nothing happens.... Why not?
-----------------------------&<----------------------
#include <stdio.h>
#include <setjmp.h>
#include <signal.h>

static jmp_buf env;

static void sigalrm(int sig)
{
  longjmp(env,sig);
}

static void install_alarm_handler(void)
{
  if (signal(SIGALRM, sigalrm) == SIG_ERR)
  {
    fprintf(stderr, "Cannot install timer\n");
    exit(1);
  };
}

static unsigned set_alarm(time)
  unsigned time;
{
  return alarm(time);
}

int main(int argc, char *argv[])
{
  if (setjmp(env) != 0)
  {
    printf("sigalrm!!\n");
    exit(0);
  };
  install_alarm_handler();
  set_alarm(1);
  while (1)
  {
    /* loop */
  };
}