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

/** Define a jump buffer to handle error conditions.
 ** Data type jmp_buf defined in setjmp.h.
 **/
static jmp_buf env; /* file scope */
#define Ok (0) 
void jumper( int ), divisionFP( void );
int guard( void );

main()
{
  /** Trap signals generated by floating-point 
   ** errors such as division by zero.
   **/
  signal( SIGFPE, jumper );

  /** Loop until error condition occurs. **/
  while ( Ok == guard() )
    ;
}

/** Jump out of this function to the jump destination,
 ** which is the point after the call to setjmp. In
 ** our case, the jump point occurs right after the
 ** if-test in function guard.
 **/
void jumper( int status )
{
  printf( "Signal status == %d.\n", status );
  longjmp( env, 1 ); 

  /** This code is executed only if longjmp fails. **/
  fprintf( stderr, "*** longjump returned!! ***\n" );
  exit( EXIT_SUCCESS );
}

/** Scan the standard input for two floats and
 ** divide the first by the second.
 **/
void divisionFP( void )
{
  float f1, f2;
  printf( "Two floats: " );
  scanf( "%f %f", &f1, &f2 );
  printf( "%f / %f == %f\n", f1, f2, f1 / f2 );
}

/** Set a jump point for return from an error 
 ** condition, in this case an error resulting
 ** from a floating-point operation. The function
 ** signal is invoked in main to trap such errors.
 ** Return Ok (0) if the floating-point operation
 ** succeeds; otherwise, the nonlocal jump
 ** of longjmp intervenes.
 **/
int guard( void )
{
  int s;

  /** Set jump point, which is right after the if-test **/
  if ( ( s = setjmp( env ) ) != Ok ) { /* jump point */
    fprintf( stderr, 
             "At jump point and about to exit...\n" );
    exit( EXIT_SUCCESS );
  }
  divisionFP();
  return Ok;
}