Question

In my template “smart pointer” class, I want to have separate constructors and assignment operators that take as arguments, respectively, lvalue and rvalue pointers. How should I write the functions?

Answer 1

In C++11 it’s really easy, because an overload accepting an rvalue reference doesn’t take precedence over one accepting an lvalue reference, but rvalues and only rvalues may bind to the former:

#include <iostream>
using std::cout;

void f(int*&) {
   cout << "lvalue_ptr ";
}

void f(int*&&) {
   cout << "rvalue_ptr ";
}

int* get_rvalue_ptr() {
   return 0;
}

int main() {
   int* ptr1;
   f(ptr1);
   f(get_rvalue_ptr());
}

// Output: lvalue_ptr rvalue_ptr 

(Obviously the above overload constructions can be applied to your member functions, too.)

I’m not sure how you’d go about it in C++03, though. I think Boost has is_rvalue that you could play with in template parameters.