I am a Fortran user that almost never used 'C' or 'C++'. But now I have to work with the three languages to one of my projects. Some of the libraries that I use depends on C99. So, my question is this: When is MS going to add full support to C99?
Microsoft supports few C99 features beyond those which are in C++11 (some only in VS2013), and those not necessarily useful for C mode. That's one of the advantages of 3rd party compilers including Intel's. In addition to separate compilers, Intel offers various licensing packages which include both Fortran and C++. Intel C++ probably includes the C99 features you need. You can get a 30-day trial of Intel compilers in order to check this. Intel Windows C++ is a plug-in for MS Visual Studio, and Intel Fortran offers the compatible modes.
We don't have any special insight into what Microsoft is doing but this is some of the latest publically available info on their C99 plans:
Additionally, some C99 Core Language features will be implemented in 2013 RTM:
* C99 _Bool
* C99 compound literals
* C99 designated initializers
* C99 variable declarations
Intel has a /Qstd=c99 command line option which enables C99 features no matter what Microsoft compatibility version you are using.