How can I avoid the LNK2005 linker error for variables defined in a header file?

Question

I have 3 cpp files that look like this

#include \"Variables.h\"
void AppMain() {
    //Stuff...
}

They all use the same variables inside th

Answer 1

I had this error too although I work with extern definitions. The problem was initializing the variables in the extern definitions too:

ID3D11VertexShader*         g_pVertexShader = nullptr;
...
extern ID3D11VertexShader*  g_pVertexShader = nullptr;  // here's the problem 

=> error

ID3D11VertexShader*         g_pVertexShader = nullptr;
...
extern ID3D11VertexShader*  g_pVertexShader;           // without initializing  

=> no error, problem solved