Is there a difference between declaring a friend function/class as private or public? I can't seem to find anything about this online.
I mean the difference between:
class A
{
public:
friend class B;
};
and
class A
{
private: //or nothing as the default is private
friend class B;
};
Is there a difference?
c++ has the notion of 'hidden friends': http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2019/p1601r0.pdf
Which only applies to friend functions that are defined inline. This make it so the functions can only be found via argument-dependent lookups, removing them from enclosing namespace.
The friend declaration appears in a class body and grants a function or another class access to private and protected members of the class where the friend declaration appears.
As such access specifiers have no effect on the meaning of friend declarations (they can appear in private: or in public: sections, with no difference).