"Q. What about the C99 Core Language, or the C11 Core Language and Standard Library?
A. Our top priority is C++ conformance. We've implemented the C99 Standard Library because C++11 incorporated it by reference. C++ (up to the current Working Paper) hasn't incorporated the C99 Core Language in its entirety (only a handful of features, listed above), nor is it ever likely to. It may incorporate the C11 Standard Library at some point in the future, but that hasn't happened yet.
In VS 2013, the compiler team implemented some C99 Core Language features in C mode (e.g. designated initializers, see MSDN for the full list), in order to support some popular libraries. "
http://blogs.msdn.com/b/vcblog/archive/2015/04/29/c-11-14-17...
"Q. What about the C99 Core Language, or the C11 Core Language and Standard Library?
A. Our top priority is C++ conformance. We've implemented the C99 Standard Library because C++11 incorporated it by reference. C++ (up to the current Working Paper) hasn't incorporated the C99 Core Language in its entirety (only a handful of features, listed above), nor is it ever likely to. It may incorporate the C11 Standard Library at some point in the future, but that hasn't happened yet.
In VS 2013, the compiler team implemented some C99 Core Language features in C mode (e.g. designated initializers, see MSDN for the full list), in order to support some popular libraries. "