Question

The following code compiles and runs perfectly,

#include <iostream>

class sam {
    public:
        void func1();
        int func2();
};

int main() {
    sam s;
}

Should it not produce a error for the lack of class member definition?

Answer 1

If you don’t call the member functions, they don’t have to be defined. Even if you call them, the compiler won’t complain since they could be defined in some other compilation unit. Only the linker will complain. Not defining functions is accepted and common to force an error for undesired behavior (e.g. for preventing copying).