How to detect LLVM Visual Studio Toolset on Windows?

We took a bug report for LLVM Visual Studio Toolset on Windows. It
appears LLVM defines _MSC_VER but it cannot consume the same programs
that Microsoft's compilers can. We now have to figure out a way to
detect Clang in this configuration and work around its shortcomings.

The "Getting Started with the LLVM System using Microsoft Visual
Studio" points us to the FAQ at http://llvm.org/docs/FAQ.html. The FAQ
does not discuss how to detect the configuration or the preprocessor
macros that are in effect.

How do we detect LLVM Visual Studio Toolset on Windows?

Hi Jeffrey,

Have you tried checking for __clang__ ?

Thanks Csaba.

The user stated the toolchain does not define some of the familiar
ones, like __clang__. From
http://github.com/weidai11/cryptopp/issues/147:

    This toolset defines MSC_VER as 1600
    __clang__ macro is not defined

I trying to get a dump of the preprocessor now to confirm it ('clang++
-dM -E - < NULL').

Jeff