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

[Bruce Hoult via cfe-dev]

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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