raise Function

Reports a synchronous signal.

Include

<signal.h>

Prototype

int raise(int sig);

Argument

Return Value

Returns a 0 if successful; otherwise, returns a non-zero value.

Remarks

raise sends the signal identified by sig to the executing program.

Example

#include <signal.h>   /* for raise, signal, */
                      /* SIGILL, SIG_DFL    */
#include <stdlib.h>   /* for div, div_t     */
#include <stdio.h>    /* for printf         */
#include <p30f6014.h> /* for INTCON1bits */

void _ ___attribute_ ___((_ ___interrupt_ ___))
_MathError(void)
{
  raise(SIGILL);
  INTCON1bits.MATHERR = 0;
}

void illegalinsn(int idsig)
{
  printf("Illegal instruction executed\n");
  exit(1);
}
int main(void)
{
  int x, y;
  div_t z;

  signal(SIGILL, illegalinsn);
  x = 7;
  y = 0;
  z = div(x, y);
  printf("Program never reaches here");
}

Example Output

Illegal instruction executed

Example Explanation

This example requires the linker script, p30f6014.gld. There are three parts to this example.

First, an interrupt handler is written for the interrupt vector, _MathError, to handle a math error by sending an illegal instruction, signal (SIGILL), to the executing program. The last statement in the interrupt handler clears the exception flag.

Second, the function illegalinsn will print an error message and call exit.

Third, in main, signal (SIGILL, illegalinsn) sets the handler for SIGILL to the function illegalinsn.

When a math error occurs due to a divide by zero, the _MathError interrupt vector is called, which in turn will raise a signal that will call the handler function for SIGILL: the function illegalinsn. Thus, error messages are printed and the program is terminated.