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Date: Mon, 5 Apr 2004 16:59:04 -0400 (EDT)
From: "Richard B. Johnson" <root@chaos.analogic.com>
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To: Jamie Lokier <jamie@shareable.org>
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       Linux kernel <linux-kernel@vger.kernel.org>
Subject: Re: Catching SIGSEGV with signal() in 2.6
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On Mon, 5 Apr 2004, Jamie Lokier wrote:

> Chris Friesen wrote:
> > SA_SIGINFO implies sigaction().  The original poster was talking about
> > signal().
> >
> > That said, it seems to work with 2.6.4 on ppc32.
>
> Just tried it with 2.6.3, x86 and signal().  Works fine.
>
> -- Jamie

Are you using a longjump to get out of the signal handler?
You may find that you can trap SIGSEGV, but you can't exit
from it because it will return to the instruction that
caused the trap!!!

#include <stdio.h>
#include <signal.h>
void handler(int sig) {
    fprintf(stderr, "Caught %d\n", sig);
}
int main() {
    char *foo = NULL;
    signal(SIGSEGV, handler);
    fprintf(stderr, "Send a signal....\n");
    kill(0, SIGSEGV);
    fprintf(stderr, "Okay! That worked!\n");
//    *foo = 0;
    return 0;
}

Just un-comment the null-pointer de-reference and watch!

Cheers,
Dick Johnson
Penguin : Linux version 2.4.24 on an i686 machine (797.90 BogoMips).
            Note 96.31% of all statistics are fiction.