sigfpe(3C)						   Standard C Library Functions 						sigfpe(3C)

NAME

       sigfpe - signal handling for specific SIGFPE codes

SYNOPSIS

       #include <floatingpoint.h>
       #include <siginfo.h>

       sigfpe_handler_type sigfpe(sigfpe_code_type code, sigfpe_handler_type hdl);

DESCRIPTION

       The sigfpe() function allows signal handling to be specified for particular SIGFPE codes.  A call to sigfpe() defines a new handler hdl for
       a particular SIGFPE code and returns the old handler as the value of the function sigfpe(). Normally handlers are specified as pointers	to
       functions;  the special cases SIGFPE_IGNORE, SIGFPE_ABORT, and SIGFPE_DEFAULT allow ignoring, dumping core using abort(3C), or default han-
       dling respectively. Default handling is to dump core using abort(3C).

       The code argument is usually one of the five IEEE754-related SIGFPE codes:

       FPE_FLTRES   fp_inexact - floating-point inexact result
       FPE_FLTDIV   fp_division - floating-point division by zero
       FPE_FLTUND   fp_underflow - floating-point underflow
       FPE_FLTOVF   fp_overflow - floating-point overflow
       FPE_FLTINV   fp_invalid - floating-point invalid operation

       Three steps are required to intercept an IEEE754-related SIGFPE code with sigfpe():

       1.  Set up a handler with sigfpe().

       2.  Enable the relevant IEEE754 trapping capability in the hardware, perhaps by using assembly-language instructions.

       3.  Perform a floating-point operation that generates the intended IEEE754 exception.

       The sigfpe() function never changes floating-point hardware mode bits affecting IEEE754 trapping.  No IEEE754-related SIGFPE  signals  will
       be generated unless those hardware mode bits are enabled.

       SIGFPE  signals	can  be  handled  using sigfpe(), sigaction(2) or signal(3C). In a particular program, to avoid confusion, use only one of
       these interfaces to handle SIGFPE signals.

EXAMPLES

       Example 1: Example Of A User-Specified Signal Handler

       A user-specified signal handler might look like this:

       #include <floatingpoint.h>
       #include <siginfo.h>
       #include <ucontext.h>
       /*
       * The sample_handler prints out a message then commits suicide.
       */
       void
       sample_handler(int sig, siginfo_t *sip, ucontext_t *uap) {
	    char *label;
	       switch (sip->si_code) {
	    case FPE_FLTINV: label = "invalid operand"; break;
	    case FPE_FLTRES: label = "inexact"; break;
	    case FPE_FLTDIV: label = "division-by-zero"; break;
	    case FPE_FLTUND: label = "underflow"; break;
	    case FPE_FLTOVF: label = "overflow"; break;
	    default: label = "???"; break;
	    }
	    fprintf(stderr, "FP exception %s (0x%x) occurred at address %p.
",
			       label, sip->si_code, (void *) sip->si_addr);
	    abort();
       }

       and it might be set up like this:

       #include <floatingpoint.h>
       #include <siginfo.h>
       #include <ucontext.h>
       extern void sample_handler(int, siginfo_t *, ucontext_t *);
       main(void) {
	     sigfpe_handler_type hdl, old_handler1, old_handler2;
       /*
	* save current fp_overflow and fp_invalid handlers; set the new
       * fp_overflow handler to sample_handler() and set the new
       * fp_invalid handler to SIGFPE_ABORT (abort on invalid)
       */
	   hdl = (sigfpe_handler_type) sample_handler;
	   old_handler1 = sigfpe(FPE_FLTOVF, hdl);
	   old_handler2 = sigfpe(FPE_FLTINV, SIGFPE_ABORT);
	   ...
       /*
	* restore old fp_overflow and fp_invalid handlers
	*/
	    sigfpe(FPE_FLTOVF, old_handler1);
	    sigfpe(FPE_FLTINV, old_handler2);
       }

FILES

       /usr/include/floatingpoint.h

       /usr/include/siginfo.h

ATTRIBUTES

       See attributes(5) for descriptions of the following attributes:

       +-----------------------------+-----------------------------+
       |      ATTRIBUTE TYPE	     |	    ATTRIBUTE VALUE	   |
       +-----------------------------+-----------------------------+
       |MT-Level		     |Safe			   |
       +-----------------------------+-----------------------------+

SEE ALSO

       sigaction(2), abort(3C), signal(3C), attributes(5), floatingpoint.h(3HEAD)

DIAGNOSTICS

       The sigfpe() function returns (void(*)())-1 if code is not zero or a defined SIGFPE code.

SunOS 5.10							    4 May 2004								sigfpe(3C)