Using libfpe.a from C

/*	This example shows how to use libfpe.a 
	from within a C program. See the 
	handle_sigfpes(3C) man page for additional 
	information.

	cc fpe_handler1.c -o fpe_handler1 -lfpe
	 ./fpe_handler1

	UNDERFLOW occurred 
	returned value for UNDERFLOW is 10.000000

	OVERFLOW occurred 
	returned value for OVERFLOW is 20.000000

	DIVIDE BY ZERO occurred 
	returned value for DIVIDE BY ZERO is 30.000000

	INVALID occurred
*/

#include <sigfpe.h> 
#include <stdio.h> 
#include <limits.h> 
#include <math.h>

void handler_rout(exception, ret_val) 
int exception[5]; 
float ret_val[2]; 

{ 
	/*	This module determines what fpe occurred 
		and sets the result of the fpe accordingly.
	*/ 

	switch(exception[_EXCEPTION_TYPE]) { 
		case _UNDERFL : 
			printf("UNDERFLOW occurred\n"); 
			ret_val[0] = 10.0; 
			break; 
		case _OVERFL : 
			printf("OVERFLOW occurred\n"); 
			ret_val[0] = 20.0; 
			break; 
		case _DIVZERO : 
			printf("DIVIDE BY ZERO occurred\n"); 
			ret_val[0] = 30.0; 
			break; 
		case _INVALID : 
			/*	There is currently a bug in the 
				libfpe.a library that prevents a 
				replacement value from being 
				assigned to `ret_val' in the case 
				of INVALID fpe. For now just 
				recognize INVALID fpe. */ 
			printf("INVALID occurred\n"); 
			break; 
	} 
}

main() 
{ 
	int i; 
	float res,min,max,zero,ten;
	/*	The elements of the sigfpe_ array are 
		interpreted as follows:
		sigfpe_[0] is ignored. 
		sigfpe_[1] is the structure for _UNDERFL 
		sigfpe_[2] is the structure for _OVERFL 
		sigfpe_[3] is the structure for _DIVZERO 
		sigfpe_[4] is the structure for _INVALID -
		Each structure contains the following:
		struct sigfpe_template 
			{ 
			int repls; The replacement value 
			int count; The count limit 
			int trace; The trace limit 
			int abort; The abort limit 
			int exit ; The exit limit 
			}; 
	*/

	/*	Initialize the sigfpe_ array to cause 
		floating point exceptions to be handled by 
		the process. The replacement value for the 
		result will be determined in handler_rout. 
	*/ 

	for (i = 1; i < _N_EXCEPTION_TYPES+1 ; i++ ) {
		sigfpe_[i].repls = _USER_DETERMINED; 
	}

	/*	Establish handler_rout() to be the module 
		to handle SIGFPEs */ 

	handle_sigfpes (_ON, \
		_EN_UNDERFL | _EN_OVERFL | _EN_DIVZERO |  _EN_INVALID, 
		(void *)handler_rout, 0, 0);

	/*	Lets generate some floating point 
		exceptions */ 

	min = FLT_MIN; 
	max = FLT_MAX; 
	ten = 10.0; 
	zero = 0.0;
	res = min/ten; 

	printf(" returned value for the UNDERFLOW is \
		%f\n\n",res);
	res = max*ten; 

	printf(" returned value for the OVERFLOW is \
		%f\n\n",res);
	res = ten/zero; 

	printf(" returned value for the DIVIDE BY \ 
		zero is %f\n\n",res);

	/* Cause an INVALID FPE. */ 
	res = zero/zero; 
}