Is there a way to export only a function to DLL cos in tutorials they always export classes with something like:
static __declspec(dllexport) double Add(double a, double b);
Inside a class the statement above does not cause any problem, but without a class it gives:
dllexport/dllimport requires external linkage
The problem is the "static" qualifier. You need to remove it because it means the wrong thing in this context. Try just:
__declspec(dllexport) double Add(double a, double b);
That's what you need to have in your header file when compiling the DLL. Now to access the function from a program that uses the DLL, you need to have a header file with this:
double Add(double a, double b);
You can use the same header file for both purposes if you use #ifdefs:
#ifndef MYDLL_EXPORT
#define MYDLL_EXPORT
#endif
MYDLL_EXPORT double Add(double a, double b);