[cfe-dev] Clang-Cl - Representation of NAN

[Bruce Hoult via cfe-dev]

That's a weird way to do it :-) But it should return
NumberFormatInfo.NanSymbol from System.Globalization, which by default
is "NaN" (though it has a setter!).

It is doesn't, then that's a bug in double.toString() and you should
take that up with Microsoft.

On Tue, Feb 5, 2019 at 2:02 AM Gaier, Bjoern <Bjoern.Gaier at horiba.com> wrote:
>
> Hey Bruce,
>
> Seems like we are not using 'double.Nan' but foo.toString and then locating there term "nan".
>
> -----Original Message-----
> From: Bruce Hoult <brucehoult at sifive.com>
> Sent: Dienstag, 5. Februar 2019 10:19
> To: Gaier, Bjoern <Bjoern.Gaier at horiba.com>
> Cc: cfe-dev at lists.llvm.org
> Subject: Re: [cfe-dev] Clang-Cl - Representation of NAN
>
> C# can handle NaN correctly. It is important NOT to do "if (foo === double.Nan)" but instead "if(double.IsNan(foo))". C# code that compares with double.NaN is simply buggy.
>
> Arithmetic should work correctly in any case.
>
> On Tue, Feb 5, 2019 at 12:29 AM Gaier, Bjoern via cfe-dev <cfe-dev at lists.llvm.org> wrote:
> >
> > Hello everyone,
> >
> >
> >
> > we are currently using clang-cl (build with LLVM7) in our project, which previously used the MSVC2017 compiler. We noticed a major difference with the representation of the NAN value.
> >
> > Clang generates 0x7FF8000000000000 for an NAN
> >
> > MSVC  generates 0xFFF8000000000000 for an NAN
> >
> >
> >
> > This difference leads to problems with C#, because it interacts with our C++ code and 'misses' the NAN.
> >
> >
> >
> > Is there a way to change the representation of the NAN via a compiler flag?
> >
> > Could we also change the source code of clang to force this representation of NAL? Or is this to much effort for a workaround?
> >
> >
> >
> > Kind greetings
> >
> > Björn
> >
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