[masklinn]

This is, as previously, support for the C standard library in its capacity as a (qualified) subset of the C++ standard library.

VS will have no more C99 support that what was previously stated by Stutter: it will support the common subset of C and C++.

[plorkyeran]

http://blogs.msdn.com/b/somasegar/archive/2013/06/28/cpp-con... lists some non-library C99 features not in C++.

[binarycrusader]

That isn't true; as part of the C++11 support Visual Studio is getting, Microsoft is implementing more of C99 language support.

To quote the blog post the other person mentioned:

...the RTM version will also include a few tactical C99 language extensions when compiling C code...

You can thank the C++11 committee for that; they worked to bring the C11 standard into the fold with C++11.

It's going to become increasingly difficult for curmudgeonly vendors to refuse to support C11 if they support C++11.