The sheer amount of code that can be compiled on every platform but VS because of this is very significant, especially open source ones. I have a hard time buying the resource reason to be honest.

. . . not actually very much. Visual Studio can use Intel's compiler, and perhaps others.

For VC++ to add support for C as easily as many compiler collections do would require VC++ having a modular architecture like that of the other compiler collections. Considering VC++ only supports one language, that seems doubtful.

Perhaps I should have said "Supporting versions of C past the point where one could plausibly just pipe the C code through a C++ compiler."

Like supporting for-loop variable declarations, which MSVC's C++ compilation mode (/TP) supports, but MSVC's C compilation mode (/TC) does not?

Oh - and what about declaring a variable anywhere other than the start of a scope? Allowed in C++, not in C. Cute.

Mission accomplished.

Any C++11 compiler that tells you it is also C11 standards compliant is not a C++11 compliant compiler. There are many things you can do with C11 that should cause an error under standards compliant C++11.

EDIT:

If they decide to make the /TP switch on the compiler turn it from C++11 compliant to C11 compliant, that basically makes it two compilers for two different languages, instead of restricting to a subset of C++11.

I'm asking for their C compiler to support the C99 or C11 standard.

They're not incompatible goals unless you're suggesting that they attempt to make a single compiler support both.