D:/msys64/mingw32/share/cmake-3.7/Modules/CheckFunctionExists.c:7:3: warning: incompatible redeclaration of library function 'ccos' [-Wincompatible-library-redeclaration]
CHECK_FUNCTION_EXISTS();
^
<command line>:1:31: note: expanded from here
#define CHECK_FUNCTION_EXISTS ccos
^
D:/msys64/mingw32/share/cmake-3.7/Modules/CheckFunctionExists.c:7:3: note: 'ccos' is a builtin with type '_Complex double (_Complex double)'