opensolaris man page for sigfpe

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 5.11							    4 May 2004								sigfpe(3C)