[cfe-dev] Clang-cl.exe and the VC++ preprocessor

[Edward Diener]

On 7/10/2014 7:22 PM, Reid Kleckner wrote:
> On Thu, Jul 10, 2014 at 3:54 PM, Edward Diener
> <eldlistmailingz at tropicsoft.com
> <mailto:eldlistmailingz at tropicsoft.com>> wrote:
>
>         As Chandler has pointed out, this is a balancing act. We try to
>         avoid
>         adding nonconforming changes to the compiler simply to be
>         bug-for-bug
>         compatible with another compiler. But we don't shy away from adding
>         them when there are valid reasons to do so. This particular
>         compatibility piece is in place in order to migrate code using MSVC
>         2012's <type_traits> header. We add others to be compatible with gcc
>         from time to time as well.
>
>
>     Would you please point out to me what in the VC12 <type_traits> does
>     not compile with a standard conforming C++ preprocessor ?
>
>
> It was the old faux-variadic macros which went away in 2013, I believe.
> http://llvm.org/PR14981

I do not understand why clang gives the error in the bug report after 
looking at the macros in the VC++ files. Would someone enlighten me 
about this ? No doubt I have missed something concerning the expansion 
of the macros.