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

[Edward Diener]

I have been told, via my bug report on a preprocessor error in the 
latest version of clang-cl.exe, that clang-cl.exe is trying to emulate 
at least some of the bugs of the VC++ preprocessor.

NO ! Please do not do that.

I know, from having worked on variadic macros in Boost PP and having 
created my own variadic macro data library, how broken the VC++ 
preprocessor is when it comes to preprocessor metaprogramming. Paul 
Mensonides, the creator of Boost PP and an exceptional expert on the C++ 
preprocessor, also knows and has bemoaned countless times how difficult 
it is to do preprocessor metaprogramming if one has to deal with the 
VC++ preprocessor. Not only will clang-cl.exe's emulation of the 
brokeness of the VC++ preprocessor set back further efforts in 
metaprogramming preprocessor code and libraries but there is absolutely 
no chance, if it means anything to clang-cl developers, that any effort 
will be made to accomodate clang-cl's preprocessor bugs into Boost PP ( 
or my own variadic macro data library ).

This is completely the wrong direction for clang-cl to go. Please stop 
and only consider producing as close to as possible a 100% C++ 
conformant preprocessor, as the rest of clang no doubt has as its goal.