This page shows that std::shared_ptr has a templated and a non-templated version of copy/move constructors ((9) and (10) on the page). Similarly, it also has two versions of copy/move assignment operator (see here).
Why do we need the non-templated version? Wouldn't the templated version alone suffice?
The templated version is not a copy constructor. According to the standard §12.8[class.copy]/2 we have that:
A non-template constructor for class X is a copy constructor if its first parameter is of type X&, const X&, volatile X& or const volatile X&, and either there are no other parameters or else all other parameters have default arguments (8.3.6).
And similarly, the templated version is also not a copy assignment operator, according to §12.8[class.copy]/17:
A user-declared copy assignment operator X::operator= is a non-static non-template member function of class X with exactly one parameter of type X, X&, const X&, volatile X& or const volatile X&.
The same holds true for move constructors (at §12.8[class.copy]/3):
A non-template constructor for class X is a move constructor if its first parameter is of type X&&, const X&&, volatile X&&, or const volatile X&&, and either there are no other parameters or else all other parameters have default arguments (8.3.6).
and move assignment operators, at §12.8[class.copy]/19:
A user-declared move assignment operator X::operator= is a non-static non-template member function of class X with exactly one parameter of type X&&, const X&&, volatile X&&, or const volatile X&&.
