Catching SIGFPE two times

[thomas.mertes@xxxxxx]

Hello

I have problems when I try to catch a division by zero for
two times. I try to emulate exceptions with setjmp/longjmp.

To catch a division by zero I use a handler for the signal
SIGFPE. In the signal handler I use longjmp to jump to the
exception handler.

What happens is: The first division by zero is handled
correctly but the second one terminates the program.
To demonstrate this, use the following test program:
--------------------------------------------------
#include "stdio.h"
#include "setjmp.h"

#define SIGFPE 8
#define SIG_IGN 1

jmp_buf catch_pos;

static void handle_fpe_signal (int sig_num)
  {
    signal(SIGFPE, handle_fpe_signal);
    printf("in handle_fpe_signal catch_pos=%lx\n", catch_pos);
    longjmp(catch_pos, 1);
  }

int main()
  {
    int fail_value;
    int x;

    signal(SIGFPE, handle_fpe_signal);
    if ((fail_value = setjmp(catch_pos)) == 0) {
      printf("before division A catch_pos=%lx\n", catch_pos);
      x = 42/0;
      printf("after division A\n");
    } else {
      printf("handler A\n");
    }
    printf("---------- A\n");

    if ((fail_value = setjmp(catch_pos)) == 0) {
      printf("before division B catch_pos=%lx\n", catch_pos);
      x = 42/0;
      printf("after division B\n");
    } else {
      printf("handler B\n");
    }
    printf("---------- B\n");

    return 0; /* Never reached */
  }
---------------------------------------------------
Compiling and execution this test program (tst3.c) gives:

tm@penguin$ cc tst3.c
tst3.c: In Funktion »main«:
tst3.c:24: Warnung: Division durch Null
tst3.c:33: Warnung: Division durch Null
tm@penguin$ ./a.out
before division A catch_pos=8049860
in handle_fpe_signal catch_pos=8049860
handler A
---------- A
before division B catch_pos=8049860
Floating point exception
tm@penguin$

Has someone an idea how a program can have more than
one SIGFPE catched with a setjmp/longjmp exception?

Greetings Thomas Mertes

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