Default value of a function pointer in C++

Question

What is the default value of a function pointer in C++? (Apparently it can\'t be NULL, so what is it?)

How is this program supposed to behave and why?

Answer 1

In C++ (and C), pointers (regardless of type) do not have a default value per se; they take what ever happens to be in memory at the time. However, they do have a default initialised value of NULL.

Default Initialisation

When you don't explicitly define a constructor, C++ will call the default initialiser on each member variable, which will initialise pointers to 0. However, if you define a constructor, but do not set the value for a pointer, it does not have a default value. The behaviour is the same for integers, floats and doubles.

Aside

int main()
{
    S s = S();
    s.f();   // <-- This is calling `f`, not getting the pointer value.
}