For the latest documentation on Visual Studio 2017 RC, see Visual Studio 2017 RC Documentation.

In effect, includes the Standard C++ library headers <ccomplex> and <cmath>, which provide type-generic math macros equivalent to <tgmath.h>.

#include <ctgmath>  

The functionality of the Standard C library header <tgmath.h> is provided by overloads in <ccomplex> and <cmath>.

Including this header ensures that the names declared using external linkage in the Standard C library header are declared in the std namespace.

Header Files Reference
STL Overview
Thread Safety in the C++ Standard Library