builtins.c:expand_errno_check() can only handle setting EDOM if the operation
returns NaN on error. Most overflow/underflow conditions result in -Inf/+Inf
instead and with non-default rounding-mode (-frounding-math) the maximum or
minimum floating-point value will be returned (round to -Inf/+Inf or zero).
One testcase:
#include <stdio.h>
#include <math.h>
#include <stdlib.h>
int main(int argc, char **argv)
{
double y = atof(argv[1]);
double x = exp (y);
printf("%.6e %.6e\n", y, x);
perror("errno");
return 0;
}
which shall print "errno: Numerical result out of range" if you pass 5000
to the testcase executable but prints "errno: Success" if you build with
-funsafe-math-optimizations on i686 which will do an inline expansion for
exp ().
--
Summary: wrong-code for errno handling on overflow/underflow
Product: gcc
Version: 4.3.0
Status: UNCONFIRMED
Keywords: wrong-code
Severity: normal
Priority: P3
Component: middle-end
AssignedTo: unassigned at gcc dot gnu dot org
ReportedBy: rguenth at gcc dot gnu dot org
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=29887
