sigfpe(3C) Standard C Library Functions sigfpe(3C)NAMEsigfpe - 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 par‐
ticular 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 sig‐
nal(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 TYPE │ ATTRIBUTE VALUE │
├─────────────────────────────┼─────────────────────────────┤
│MT-Level │Safe │
└─────────────────────────────┴─────────────────────────────┘
SEE ALSOsigaction(2), abort(3C), signal(3C), attributes(5), floating‐
point.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)
