sigfpe(3)               (BSD Compatibility Package)               sigfpe(3)


   NAME
         sigfpe - signal handling for specific SIGFPE codes

   SYNOPSIS
         cc [ flag... ] file ... -lucb

         #include <signal.h>

         #include <floatingpoint.h>

         sigfpehandlertype sigfpe(code, hdl)
         sigfpecodetype code;
         sigfpehandlertype hdl;

   DESCRIPTION
         This 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 SIGFPEIGNORE, SIGFPEABORT, and
         SIGFPEDEFAULT allow ignoring, specifying core dump using abort(3),
         or default handling respectively.

         For these IEEE-related codes:

                FPEFLTINEX    fp_inexact     floating inexact result
                FPEFLTDIV     fp_division    floating division by zero
                FPEFLTUND     fp_underflow   floating underflow
                FPEFLTOVF     fp_overflow    floating overflow
                FPEFLTOPERR   fp_invalid     floating operand error
                FPEFLTNAN     fp_invalid     floating Not-A-Number

         default handling is defined to be to call the handler specified to
         ieeehandler(3M).

         For all other SIGFPE codes, default handling is to core dump using
         abort(3).

         The compilation option -ffpa causes fpa recomputation to replace the
         default abort action for code FPEFPAERROR.  Note:  SIGFPEDEFAULT
         will restore abort rather than FPA recomputation for this code.

         Three steps are required to intercept an IEEE-related SIGFPE code
         with sigfpe:

               1)    Set up a handler with sigfpe.

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



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   sigfpe(3)               (BSD Compatibility Package)               sigfpe(3)


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

         Unlike ieeehandler(3M), sigfpe never changes floating-point hardware
         mode bits affecting IEEE trapping.  No IEEE-related SIGFPE signals
         will be generated unless those hardware mode bits are enabled.

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

   EXAMPLE
         A user-specified signal handler might look like this:

         void samplehandler( sig, code, scp, addr )
                 int sig ;               /* sig == SIGFPE always */
                 int code ;
                 struct sigcontext *scp ;
                 char *addr ;
                 {
                         /*
                            Sample user-written sigfpe code handler.
                            Prints a message and continues.
                            struct sigcontext is defined in <signal.h>.
                          */
                         printf(" ieee exception code %x occurred at pc %X \n",
                                 code,scp->scpc);
                 }

         and it might be set up like this:

                 extern void samplehandler;
                 main
                 {
                         sigfpehandlertype hdl, oldhandler1, oldhandler2;
                 /*
                  * save current overflow and invalid handlers; set the new
                  * overflow handler to samplehandler and set the new
                  * invalid handler to SIGFPEABORT (abort on invalid)
                  */
                         hdl = (sigfpehandlertype) samplehandler;
                         oldhandler1 = sigfpe(FPEFLTOVFTRAP, hdl);
                         oldhandler2 = sigfpe(FPEFLTOPERRTRAP, SIGFPEABORT);
                         ...
                 /*
                  * restore old overflow and invalid handlers
                  */
                         sigfpe(FPEFLTOVFTRAP,   oldhandler1);
                         sigfpe(FPEFLTOPERRTRAP, oldhandler2);
                 }



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   sigfpe(3)               (BSD Compatibility Package)               sigfpe(3)


   FILES
         /usr/include/floatingpoint.h
         /usr/include/signal.h

   SEE ALSO
         sigvec(2), floatingpoint(3), ieeehandl(3),

         abort(3C) in the Programmer's Reference Manual.

   RETURN VALUE
         sigfpe returns BADSIG if code is not zero or a defined SIGFPE code.










































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