/* FPRESET.C: This program uses signal to set up a
* routine for handling floating-point errors.
*/
#include <stdio.h>
#include <signal.h>
#include <setjmp.h>
#include <stdlib.h>
#include <float.h>
#include <math.h>
#include <string.h>
jmp_buf mark; /* Address for long jump to jump to */
int fperr; /* Global error number */
void __cdecl fphandler( int sig, int num ); /* Prototypes */
void fpcheck( void );
int main( void )
{
double n1, n2, r;
int jmpret;
int ch;
/* Unmask all floating-point exceptions. */
_control87( 0, _MCW_EM );
/* Set up floating-point error handler. The compiler
* will generate a warning because it expects
* signal-handling functions to take only one argument.
*/
// if( signal( SIGFPE, fphandler ) == SIG_ERR )
if( signal( SIGFPE, (void (__cdecl *)(int)) fphandler ) == SIG_ERR )
{
fprintf( stderr, "Couldn't set SIGFPE\n" );
abort(); }
/* Save stack environment for return in case of error. First
* time through, jmpret is 0, so true conditional is executed.
* If an error occurs, jmpret will be set to -1 and false
* conditional will be executed.
*/
jmpret = setjmp( mark );
// printf( "\n%lf\n" , jmpret );
if( jmpret == 0 )
{
printf( "Test for invalid operation - enter two numbers: \n" );
printf( "First nr: \n");
scanf( "%lf", &n1 );
printf( "Second nr: \n");
scanf( "%lf", &n2 );
r = n1 / n2;
/* This won't be reached if error occurs. */
printf( "\n\n%4.3g / %4.3g = %4.3g\n", n1, n2, r );
r = n1 * n2;
/* This won't be reached if error occurs. */
printf( "\n\n%4.3g * %4.3g = %4.3g\n", n1, n2, r );
}
else
fpcheck();
ch = getchar();
ch = getchar();
}
/* fphandler handles SIGFPE (floating-point error) interrupt. Note
* that this prototype accepts two arguments and that the
* prototype for signal in the run-time library expects a signal
* handler to have only one argument.
*
* The second argument in this signal handler allows processing of
* _FPE_INVALID, _FPE_OVERFLOW, _FPE_UNDERFLOW, and
* _FPE_ZERODIVIDE, all of which are Microsoft-specific symbols
* that augment the information provided by SIGFPE. The compiler
* will generate a warning, which is harmless and expected.
*/
void fphandler( int sig, int num )
{
/* Set global for outside check since we don't want
* to do I/O in the handler.
*/
fperr = num;
printf( "Error %d::: \n", fperr );
/* Initialize floating-point package. */
_fpreset();
/* Restore calling environment and jump back to setjmp. Return
* -1 so that setjmp will return false for conditional test.
*/
longjmp( mark, -1 );
}
void fpcheck( void )
{
char fpstr[30];
switch( fperr )
{
case _FPE_INVALID:
strcpy( fpstr, "Invalid number" );
break;
case _FPE_OVERFLOW:
strcpy( fpstr, "Overflow" );
break;
case _FPE_UNDERFLOW:
strcpy( fpstr, "Underflow" );
break;
case _FPE_ZERODIVIDE:
strcpy( fpstr, "Divide by zero" );
break;
default:
strcpy( fpstr, "Other floating point error" );
break;
}
printf( "Error %d: %s\n", fperr, fpstr );
}