17 Language support library [support]

17.14 C headers [support.c.headers]

17.14.6 Header <tgmath.h> synopsis [tgmath.h.syn]

#include <cmath> #include <complex>
The header <tgmath.h> behaves as if it simply includes the headers <cmath> and <complex>.
[Note 1: 
The overloads provided in C by type-generic macros are already provided in <complex> and <cmath> by “sufficient” additional overloads.
— end note]
[Note 2: 
Names introduced by <cmath> or <complex> in namespace std are not placed into the global namespace scope by <tgmath.h>.
— end note]