c++ - Friend declaration and explicit template instantiation declaration

Question

Suppose I have a function template

template <typename T>
void f(T) {}

Then, we could have a friend declaration

friend void f<int>(int);

and an explicit template instantiation declaration

extern template void f<int>(int);

Are the two declarations related in some way or totally independent? If related, how do they interact with each other?

Answer 1

friend声明不与任何事物“交互”，除了声明为友元的函数定义，允许访问包含声明的类的私有成员。

friend所以，不，声明和声明之间没有特殊的交互extern template，尽管它们都引用同一个函数（从这个意义上说，它们是相关的，但我假设你在写问题时意识到了这一点）。