Hi,
> Note that "will ever set errno" includes possibly setting it in the
> future, since code may be built with one libm version and used with
> another. So it wouldn't be correct to have a "never sets errno" attribute
> on glibc logb / lround / llround / lrint / llrint / fma / remquo (missing
> errno setting is a known bug).
If these functions should set errno, there are many issues both in GCC and
GLIBC. GCC treats fma and remquo always as const/pure, so inlines fma
always even with -fmath-errno. GLIBC targets which support fma as a
single instruction always inline it as a single instruction, as expected.
GCC incorrectly treats many other math functions as const/pure, for
example GCC "knows" that the C89 sin function will never set errno with
-fmath-errno:
#include <math.h>
#include <errno.h>
int res;
double f(double x)
{
errno = 0;
double y = sin (x);
res = errno;
return y;
}
So if anything this is good evidence that nobody is using errno in actual
applications, otherwise these bugs would have been found many years ago.
Wilco
