This is the mail archive of the
libc-alpha@sourceware.org
mailing list for the glibc project.
Re: Fix pow (0.0, -Inf) (bug 14241)
On Fri, 15 Jun 2012, Andreas Jaeger wrote:
> - if (ABS(y) > 1.0e20) return (y>0)?0:INF.x;
> + if (ABS(y) > 1.0e20) return (y>0)?0:1.0/ABS(x);
> k = checkint(y);
> if (k == -1)
> return y < 0 ? 1.0/x : x;
>
> Can't we just revert this - just using INF.x in both places? Why do we need
> the division here?
When y is finite, the divide-by-zero exception is required, which means
the division must be executed. It's the case of infinite y where ideally
there would be no exception (as per the IEEE 754 semantics that
divide-by-zero exceptions are for exact infinities as results for
operations on *finite* operands) and C11 makes the exception optional.
--
Joseph S. Myers
joseph@codesourcery.com