Yes, 2013 added support for most of it and 2015 adds a few more things.

Specifically, in 2015 our C99 Standard Library implementation is complete, except for tgmath.h (irrelevant in C++) and the CX_LIMITED_RANGE/FP_CONTRACT pragma macros.

Huh... Didn't know STL was on HN.. Good to see you here! :)

When I was 16 years old I would get into the nuwen IRC where I learned and really started my whole programming education / career through STL. I still remember the std::vector explanation that included cats in buckets. Prior to him I only opened VB's IDE and...that was it. He had me writing algorithms in C++.

Too bad I'm so rusty in C++ nowadays; need to get back on it. I like using the nuwen MinGW distro when I worked on Windows; made picking up boost and SDL really simple.

(Just figured I'd share since you mentioned him; he probably doesn't remember me at all but without him I don't know if I would have ever become a developer. In fact at the time I was thinking about becoming a doctor but was a lazy high schooler who dreaded the years of education required)

Ha, that's cool to hear!

Back when I first had the shock of discovering that VS only supported C89 I remember poking around to figure out why and finding a rant from a higher-up on the compiler team along the lines of "C is a dead language, just use C++." What happened? Did he leave? Did an order come down from on high? Did he mellow with age?

Our current statement of support is that we support enough of C99 to unblock commonly used libraries. We support a large swath of C99 but it is correct that our support isn't complete yet as we prioritized C++ conformance. If there is a C99 library that you need to use that we don't work with, please let me know. (I'm the VC++ dev manager)

It seems that MSVC really has improved its support for C99, though, and I'm glad about that. What about C11? Does it support _Atomic/stdatomic.h? I can't tell from Googling, and I'm too tired to install the CTP tonight... If it does, it'd be ahead of OS X, hopefully not for long. The C11/C++11 memory model is powerful, way nicer to use than volatile plus OS-specific library functions, and, compared to other features, it's difficult to properly implement as a shim. It's too bad that only C++ can take advantage of it on some platforms.

Existing libraries are one thing, but when writing new code (and yes, I want to write new code in C), one of the big three compilers not supporting a feature is strong motivation not to use it... even if it would be really nice to have. Maybe in the coming years Clang will improve its Windows support enough that I can just tell everyone to swap it in for cl.exe, so I won't have to care about MSVC's standards support, but for now it and GCC are missing a lot of features on Windows.

The C11 Standard Library has not been incorporated into any C++ Standard (not even the C++17 Working Paper as of right now), so we have not attempted to support it. On the other hand, our C++11 <atomic> implementation has been significantly improved in VC 2015.

I believe the choice was to spend time on adding C99 support, vs spending more time on C++ support. C++ had more people asking for it, so it got priority over C99.

Doesn't the latest C++ standard more or less include C99?

Only the C99 standard library. The language changes which weren't already part of C++ weren't imported.

I haven't used Visual Studio to compile C in a long long time, but does it support compiling files as C files as well? For example:

char ptr = malloc(10); // this is not valid C++

vs

char ptr = (char *)malloc(10); // This is usually required for Visual C++ (or was).

Yes, on the properties of the file you can specify whether to compile as C or C++. It can also be set as a project default.

I believe files with the .c extensions are compiled as C, not C++.

Please edit to add an asterisk in front of ptr in both cases.

It's the markdown getting in the way. You can tell by the varying italics.

Indeed. Still needs to be fixed.

complex.h seems very incomplete.

It does if you compile with Clang - VS is just a front-end after all. If you're asking about MSVC however, it's incomplete.