C99

Visual Studio 首次引入C99的语言特性和库函数的支持，但只支持有限的语言特性：

_BoolCompound literals.Designated initializers.Mixing declarations with code.

Visual Studio 实现了基本所有的库函数支持

参考：

C99 library support in Visual Studio - C++ Team Blog

Visual C++ What’s New through | Microsoft Docs

C Runtime (CRT) Features, Fixes, and Breaking Changes in Visual Studio 14 CTP1

Microsoft C/C++ language conformance | Microsoft Docs

C11/C17

Visual Studio 16.8 Preview 3 引入C11和C17(不完整)支持，使用命令行选项/std:c11 或 /std:c17 来启用

参考：

C11 and C17 Standard Support Arriving in MSVC

Microsoft C/C++ language conformance | Microsoft Docs