Content-type: text/html Man page of sigfpe

sigfpe

Section: Standard C Library Functions (3C)
Updated: 4 May 2004
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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 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.

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.\n",
                        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 TYPEATTRIBUTE VALUE
MT-LevelSafe

 

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.


 

Index

NAME
SYNOPSIS
DESCRIPTION
EXAMPLES
FILES
ATTRIBUTES
SEE ALSO
DIAGNOSTICS

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Time: 02:37:25 GMT, October 02, 2010