Manual Pages for UNIX Operating System command usage for man sigfpe

Standard C Library Functions                           sigfpe(3C)



NAME
     sigfpe - signal handling for specific SIGFPE codes

SYNOPSIS
     #include 
     #include 

     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  handling
     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.




SunOS 5.11           Last change: 4 May 2004                    1






Standard C Library Functions                           sigfpe(3C)



     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 
       #include 
       #include 
       /*
       * 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.\n",
               label, sip->si_code, (void *) sip->si_addr);
            abort();
       }



     and it might be set up like this:


       #include 
       #include 
       #include 
       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);



SunOS 5.11           Last change: 4 May 2004                    2






Standard C Library Functions                           sigfpe(3C)



           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  attri-
     butes:



     ____________________________________________________________
    |       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           Last change: 4 May 2004                    3