Thanks again. I��ve added a note to the issue, and raised a bug<https://sourceforge.net/p/mingw-w64/bugs/916/> against mingw. (And also updated another<https://sourceforge.net/p/mingw-w64/bugs/515/> related one.) Is the right solution here to get it fixed in mingw? (And would that then be picked up in some future Haskell release?). I��m also still a bit confused about ming-w64 and GCC (which are all very new to me). Per Wikipedia<https://en.wikipedia.org/wiki/Mingw-w64> ��Mingw-w64 includes a port of the GNU Compiler Collection (GCC)��. So why does it have two different implementations of asinh? �C one for use by GCC (that gives good results), and one that is called at runtime (that gives bad results)?. Thanks! David. From: arata, mizuki<mailto:minorinoki@gmail.com> Sent: 04 September 2021 12:41 To: David James<mailto:dj112358@outlook.com> Cc: haskell-cafe@haskell.org<mailto:haskell-cafe@haskell.org> Subject: Re: [Haskell-cafe] Trouble with asinh (c calls with Doubles) in Windows FloatFnInverses is marked as ��expect_broken�� on Windows: https://gitlab.haskell.org/ghc/ghc/-/blob/922c6bc8dd8d089cfe4b90ec2120cb4895... And there��s a relevant issue: https://gitlab.haskell.org/ghc/ghc/-/issues/15670 Mizuki 2021/09/04 18:46��David James <dj112358@outlook.com<mailto:dj112358@outlook.com>>��`��: Hi - thank you for this. I was unaware of the ��constant folding�� in GCC (and I��m surprised it works for functions like asinh), but I can see that it explains the difference in behaviour. So I think this is a (possibly minor) bug that Haskell inherits from mingw-w64. I guess I should raise a GHC issue �C though I��m not sure whether it would be best to try to fix within Haskell or within mingw-w64. Also, I think the FloatFnInverses.hs<https://gitlab.haskell.org/ghc/ghc/-/blob/master/testsuite/tests/numeric/should_run/FloatFnInverses.hs> test doesn��t should be showing as a fail somewhere in the CI testing. (It doesn��t give the expected output when I run it on Windows). Do you know whether/where I can see that? (I don��t know what CI happens or how to view its output). Thanks again, David. From: arata, mizuki<mailto:minorinoki@gmail.com> Sent: 03 September 2021 13:43 To: David James<mailto:dj112358@outlook.com> Cc: haskell-cafe@haskell.org<mailto:haskell-cafe@haskell.org> Subject: Re: [Haskell-cafe] Trouble with asinh (c calls with Doubles) in Windows Hi David, If I understand correctly, GHC uses mingw-w64��s libc implementation on Windows. Since mingw-w64��s math functions are not of very good quality, it is likely that asinh returns NaN for a very large input. As to why `asinh(1.7976931348623157e308)` in CAsinh.c produces (seemingly-correct) 710.4758, it is probably because the C compiler (GCC) uses a different implementation of asinh when doing constant folding. As a note, you may get a different (compile-time computed) result for `asinh(x)` if you set a more aggressive optimization flag. Mizuki