Re: isnan function conflicts with C++ standard library declarations

[Martin Storsjö]

On Wed, 28 Aug 2019, Bruno Haible wrote:

> > > > This issue can crop up e.g. when trying to build gettext for mingw (which
> > > > has got the gnulib isnan function bundled, even if it isn't used).
> > >
> > > I'm regularly building gettext on mingw and haven't seen this issue. Therefore
> > > thanks again for the reproduction example.
> >
> > I ran into it while trying to build gettext with clang (with my pure-llvm
> > based toolchain, at https://github.com/mstorsjo/llvm-mingw in case you're
> > interested), so I presume there's something that goes different in gettext
> > with clang/lld compared to gcc
>
> Yes. It would make sense to compare the config.status file generated by an llvm
> build with those generated by a gcc build.

Just for the record, I believe the root cause is the fact that libc++'s 
stdlib.h (which is included before the normal C runtime's stdlib.h) 
includes math.h since this change: https://reviews.llvm.org/D60097

So math.h ends up included at a place where it isn't, when building with 
libstdc++, exposing the incompatibility between the gnulib math.h's isnan 
and C++, while other builds of the C++ code in gettext wouldn't include 
math.h at all.

// Martin