Fix missing overflow exceptions from pow (bug 13873)

[Andreas Jaeger]

On 04/09/2012 12:04 AM, Joseph S. Myers wrote:
> Bug 13873 is a failure of pow to raise overflow exceptions on x86_64
> when the absolute value of the exponent is so large that taking that
> power of any floating-point value other than plus or minus zero, one,
> infinity or NaN would overflow or underflow.  I propose this patch to
> fix this bug by doing computations at runtime that overflow or
> underflow as required, as done in various other places in libm.  (The
> "huge" and "tiny" constants are the same as used for this purpose
> elsewhere in dbl-64, so will be merged with the other instances since
> glibc is built with -fmerge-all-constants.)
>
> Tested x86 and x86_64.
>
> 2012-04-08  Joseph Myers<joseph@codesourcery.com>
>
> 	[BZ #13873]
> 	* sysdeps/ieee754/dbl-64/e_pow.c (huge, tiny): New variables.
> 	(__ieee754_pow): Generate overflow and underflow using huge*huge
> 	and tiny*tiny rather than just returning constant infinity or zero
> 	for large exponents.
> 	* math/libm-test.inc (pow_test): Require overflow exceptions for
> 	applicable cases of large exponents.

thanks, this is fine,
Andreas
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