Re: Odd error I can't seem to recreate

On Nov 4, 11:52 am, Noah Roberts <roberts.n...@gmail.com> wrote:


Here's a further revision of the problem code:

 cat wtf.cpp
#include <memory>
#include <iostream>

struct base
{
        virtual ~base() {}
        virtual void f() const = 0;
};

struct derived : base
{
#ifdef HUH
private:
  derived(derived const&);
#endif
public:
        derived() {}
        void f() const { std::cout << "derived::f() \n"; }
};

struct base;
struct base2
{
        virtual ~base2() {}
        virtual void fun(base const&) const = 0;
};
struct derived2 : base2
{
        void fun(base const& b) const { b.f(); }
};

struct base3
{
        virtual ~base3() {}
        virtual std::auto_ptr<base2> get() const = 0;
};
struct derived3 : base3
{
        std::auto_ptr<base2> get() const { return
std::auto_ptr<base2>(new derived2); }
};

int main()
{
        derived3 d3;
        std::auto_ptr<base2> b2 = d3.get();
        b2->fun(derived());
}

The result of compilation and run without -DHUH:

$ g++ wtf.cpp
$ ./a.out
derived::f()

The result with -DHUH:
$ g++ -DHUH wtf.cpp
wtf.cpp: In function =E2int main()=E2:
wtf.cpp:14: error: =E2derived::derived(const derived&)=E2 is private
wtf.cpp:47: error: within this context

So it appears that the problem is with the temporary being created,
and that I don't understand. As far as I knew, const reference
allowed you to use the initially created temporary directly. Where's
the standard text that explains why it's doing this?