SIGFPE captured repeatedly..

SIGFPE captured repeatedly..

[Vijayekkumaran.M]

Hi,

I am trying to write a small program which handles
SIGFPE..
The problem is that the handler is called infinitely..

Could somebody please tell me what I am missing..?
Please find the program below..

"Red Hat Linux release 7.3 (Valhalla)
Kernel 2.4.18-3 on an i686
gcc version 2.96"

Regards
Vijay

/*********************************************/
#include <signal.h>
#include <stdio.h>

void sig_s(int signo)
{
 printf("Hai Division by zero:Floation point
exception\n");
 /*signal(SIGFPE,sig_s);*/
}

#define BUFFER_SIZE 1024

int main()
{
 int i,j,z;
 char Buffer[BUFFER_SIZE];
 int x;
 FILE* fp = fdopen(0,"r");
 signal(SIGFPE,sig_s);
 
 for(x=0;x<5;x++)
 {
  fflush(fp);
  i=0;j=0;
  printf("Accepted i = %d and j= %d \n",i,j);
  z = i/j;
  printf("Result = %d\n",z);
 }
 return 0;
}
/*********************************************/


		
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RE: SIGFPE captured repeatedly..

[Ganesh_Borse]

See 4th paragraph in Notes section in "man signal"

-----Original Message-----
From: linux-c-programming-owner@vger.kernel.org
[mailto:linux-c-programming-owner@vger.kernel.org]On Behalf Of
Vijayekkumaran.M
Sent: Thursday, September 02, 2004 5:07 PM
To: linux-c-programming@vger.kernel.org
Subject: SIGFPE captured repeatedly..


Hi,

I am trying to write a small program which handles
SIGFPE..
The problem is that the handler is called infinitely..

Could somebody please tell me what I am missing..?
Please find the program below..

"Red Hat Linux release 7.3 (Valhalla)
Kernel 2.4.18-3 on an i686
gcc version 2.96"

Regards
Vijay

/*********************************************/
#include <signal.h>
#include <stdio.h>

void sig_s(int signo)
{
 printf("Hai Division by zero:Floation point
exception\n");
 /*signal(SIGFPE,sig_s);*/
}

#define BUFFER_SIZE 1024

int main()
{
 int i,j,z;
 char Buffer[BUFFER_SIZE];
 int x;
 FILE* fp = fdopen(0,"r");
 signal(SIGFPE,sig_s);
 
 for(x=0;x<5;x++)
 {
  fflush(fp);
  i=0;j=0;
  printf("Accepted i = %d and j= %d \n",i,j);
  z = i/j;
  printf("Result = %d\n",z);
 }
 return 0;
}
/*********************************************/


		
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RE: SIGFPE captured repeatedly..

[Colovic (ext_evosoft) Aleksandar]

Hi,


here is slightly modified code:

#include <signal.h>
#include <stdio.h>

static int j;

void sig_s(int signo)
{
	j = 3;
 	printf("Hai Division by zero:Floation point exception\n");

}

#define BUFFER_SIZE 1024

int main()
{
 int i,z;
 char Buffer[BUFFER_SIZE];
 int x;
 FILE* fp = fdopen(0,"r");
 signal(SIGFPE,&sig_s);

 for(x=0;x<5;x++)
 {
  fflush(fp);
  i=0;j=0;
  printf("Accepted i = %d and j= %d \n",i,j);
  z = i/j;
  printf("Result = %d\n",z);
 }
 return 0;
}
/*********************************************/

Explanation: In case of 'divide error' system sends SIGFPE to your process.
Default action would be core dump and abortion of the
process, but since you installed an exception handler for this signal,
system expects that your signal handler somehow corrects invalid 
situation and transfers control again to problematic division. Since you
didn't corrected the problem, CPU raises again 'divide error' exception and
system's exception handler (divide_error()) sends again SIGFPE to your
signal handler ....

In the code above, I declared problematic j variable as static and corrected
its value in the signal handler ... so loop continues and everything's well.

I hope, this helps

Aleksandar Colovic,