Hi, On Wed, Apr 16, 2014 at 11:50 AM, Kai Tietz <ktiet...@googlemail.com> wrote: > Hello Matthew, > > 2014-04-16 20:36 GMT+02:00 Matthew Brett <matthew.br...@gmail.com>: >> Hi, >> >> Sorry for my ignorance about mingw-w64 - I am hoping for advice on >> submitting a patch. >> >> When testing against the Python numpy library, we found a failing test >> for the mingw-w64 expm1 routine. Specifically, we found that: >> >> double i = -0.0; >> return expm1(i); >> >> returns 0 instead of -0, as I believe the standard requires: >> >> http://pubs.opengroup.org/onlinepubs/9699919799/functions/expm1.html >> http://lists.gnu.org/archive/html/bug-gnulib/2012-03/msg00029.html >> https://github.com/gagern/gnulib/blob/master/tests/test-expm1-ieee.h > > So thanks for showing to us this bug. Math tests are a bit wacky in > general. I use normally netbsd test for validation. Nevertheless > this works only in some aspects for Windows, so we have some > additional tests in our crt's testcases directory. > > At this place I would think your testcase should go. > >> The following patch fixes this: >> >> diff -r -u mingw-w64-v3.1.0/mingw-w64-crt/math/expm1.def.h >> b/mingw-w64-crt/math/expm1.def.h >> --- mingw-w64-v3.1.0/mingw-w64-crt/math/expm1.def.h 2014-04-14 >> 20:41:33.000000000 -0700 >> +++ b/mingw-w64-crt/math/expm1.def.h 2011-04-02 09:58:41.000000000 -0700 >> @@ -60,7 +60,7 @@ >> } >> else if (x_class == FP_ZERO) >> { >> - return __FLT_CST(0.0); >> + return (signbit (x) ? -__FLT_CST(0.0) : __FLT_CST(0.0) > > Hmm, as x is in that case zero, wouldn't it be better just to return x here?
Ah - yes - that is better, thanks.
>> }
>> if (__FLT_ABI (fabs) (x) < __FLT_LOGE2)
>> {
>>
>> but I don't know how to submit tests for the change. What do y'all advise?
>>
>> Thanks a lot,
>
>
> A test checking exactly this case (or the set of cases for expm1) is welcome.
>
> Please also provide an ChangeLog entry, so we can prominent mark your
> code-donation.
OK, I have attached a patch - with apologies for my rusty C macro skills.
Thanks a lot,
Matthew
expm1_minus_zero.patch
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