c++ - Assigning value to a parameter passed to an extern C function -

I have 2 different projects in 2 different functions:

The function in P1.cpp is:

Specify zero paragraph () {int x = 0; ChangeValue (x); // value of x is still 0}

P2.cpp

  extern "c" __declspec (dllexport) int change (int x = 0) { X = 5; Return 0; }

How to make X value 5?

How to assign values to parameters in the External C function

Brayer