[Bug c++/59926] New: Remove temporary move constructor before move assignment

[arnoux123 at gmail dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=59926

            Bug ID: 59926
           Summary: Remove temporary move constructor before move
                    assignment
           Product: gcc
           Version: unknown
            Status: UNCONFIRMED
          Severity: enhancement
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: arnoux123 at gmail dot com

When returning an rvalue from a function, the compiler creates a temporary
using
"move constructor" before doing a "move assignment" to the object in the
calling
function. See code below.
Would it be possible to remove this temporary "move constructor" which seems
somewhat redundant.

#include <iostream>
#include <utility>
#include <string>

class Base
{
public:
        Base() { std::cout << this << " Base ctor\n" ; }
        ~Base() { std::cout << this << " Base dtor\n" ; }
        Base(Base const&) { std::cout << this << " Base copy\n" ; }
        Base& operator=(Base const&) { std::cout << this << " Base copy
assign\n" ; return *this; }
        Base(Base&&) { std::cout << this << " Base move\n" ; }
        Base& operator=(Base&&) { std::cout << this << " Base move assign\n" ;
return *this; }
};

class Derived : public Base
{
public:
        Derived(): Base() { std::cout << this << " Derived ctor\n" ; }
        ~Derived() { std::cout << this << " Derived dtor\n" ; }
        Derived(Derived const& o): Base(o) { std::cout << this << " Derived
copy\n" ; }
        Derived(Derived&& o): Base(std::move(o)) { std::cout << this << "
Derived move\n" ; }
        Derived& operator=(Derived const& o) { std::cout << this << " Derived
copy assign\n" ; return (*this) ; }
        Derived& operator=(Derived&& o) { std::cout << this << " Derived move
assign\n" ; Base::operator=(std::move(o)) ; return (*this) ; }
};

Derived f(Derived d) { return (d) ; }

int main()
{
        Derived r ;
        Derived u ;
        u = f(r) ;
        return 0;
}