Undefined reference to a static member

Question

I'm using a cross compiler. My code is:

class WindowsTimer{ public:   WindowsTimer(){     _frequency.QuadPart = 0ull;   }  private:   static LARGE_INTEGER _frequency; }; 

I get the following error:

undefined reference to `WindowsTimer::_frequency'

I also tried to change it to

LARGE_INTEGER _frequency.QuadPart = 0ull; 

or

static LARGE_INTEGER _frequency.QuadPart = 0ull; 

but I'm still getting errors.

anyone knows why?

Answer 1

You need to define _frequency in the .cpp file.

i.e.

LARGE_INTEGER WindowsTimer::_frequency; 

Answer 2

With C++17, you can declare your variable inline, no need to define it in a cpp file any more.

inline static LARGE_INTEGER _frequency;