[LCP]SIGFPE

[devraj sanyal]

setjmp lngjmp doesnot help since the kernel
dispatches the signal again and again until
the condition of fpe is removed. 

e.g. 
int i = 0;
SigHandler(int sig)
{
	i = 5;
}

int main ()
{
	int j;
	signal (SIGFPE, SigHandler);
	j= 10/i;
	printf ("here i am");
	return 0;
}


this program works fine and here i am is printed
but without changing i the loop is infinite.

devraj



On Thu, 11 Jul 2002 Jack Lloyd wrote :
>Well, it actually only says that ignoring this signal can result in an
>infinte loop. I would presume this means using SIG_IGN, rather than
>requiring that the signal handler must abort.
>
>There is a workaround to this. Basically, use setjmp and longjmp. Do a
>setjmp right before you do the potentially bad instruction, and do a
>longjmp out of the signal handler.
>
>I'm not totally sure that you're allowed to do longjmp inside a signal
>handler (actually, I'm pretty sure it's undefined by POSIX). But I've seen
>it done in several pieces of reasonable portable pieces of software. I've
>never done this for SIGFPE but I've seen it for SIGILL and done it myself
>for SIGPIPE.
>
>-Jack
>
>On 11 Jul 2002, devraj  sanyal wrote:
>
> > This is the default behaviour of the kernel.
> > on sigfpe the kernel loops on the signal
> > again and again. check out the man page
> > for signal.
> >
> >
> >
> >
> > On Thu, 11 Jul 2002 madhav morje wrote :
> > >Hello,
> > >
> > >I'm a novice in signal field. I was trying to out a simple
> > >program (which I've pasted below). When the binary was executed,
> > >signal handler for SIGFPE was executed continuously even though
> > >I've written a signal handler for it.
> > >
> > >My query is, why kernel continuously gives this signal to my
> > >program Or Am I missing something in my code??
> > >
> > >If I reset signal handler for SIGFPE to defualt one in the signal
> > >handler function, then my program gets terminated.
> > >
> > >Regards,
> > >Madhav.
> > >
> > >======================================================
> > >#include <signal.h>
> > >#include <stdio.h>
> > >#include <unistd.h>
> > >
> > >void sighand(int sig)
> > >{
> > >  printf("\nSig Recd %d", sig);
> > >  /*
> > >  ** Should signal handler be reset here for SIGFPE to default
> > >here ????
> > >  */
> > >}
> > >
> > >int main()
> > >{
> > >
> > >struct sigaction act;
> > >int j=10,k;
> > >
> > >act.sa_handler = sighand;
> > >sigemptyset(&act.sa_mask);
> > >act.sa_flags = 0;
> > >
> > >sigaddset(&act.sa_mask, SIGFPE);
> > >
> > >(void) sigaction(SIGFPE, &act, 0);
> > >
> > >k=j/0;
> > >
> > >printf("\ndone!!\n");
> > >
> > >return 0;
> > >
> > >}
> > >======================================================
> > >_________________________________________________________
> > >There is always a better job for you at Monsterindia.com.
> > >Go now http://monsterindia.rediff.com/jobs
> > >
> > >
> > >_______________________________________________
> > >This is the Linux C Programming List
> > >:  http://lists.linux.org.au/listinfo/linuxcprogramming List
> >
> > _________________________________________________________
> > There is always a better job for you at Monsterindia.com.
> > Go now http://monsterindia.rediff.com/jobs
> >
> >
> > _______________________________________________
> > This is the Linux C Programming List
> > :  http://lists.linux.org.au/listinfo/linuxcprogramming List
> >
>
>
>_______________________________________________
>This is the Linux C Programming List
>:  http://lists.linux.org.au/listinfo/linuxcprogramming List

_________________________________________________________
There is always a better job for you at Monsterindia.com.
Go now http://monsterindia.rediff.com/jobs