Re: Why does this compile with VC++?

From:

"Victor Bazarov" <v.Abazarov@comAcast.net>

Newsgroups:

microsoft.public.vc.language

Date:

Wed, 28 Feb 2007 08:26:00 -0500

Message-ID:

<es3vt9$mcn$1@news.datemas.de>

Duane Hebert wrote:

"Defect Architect" <DefectArchitect@discussions.microsoft.com> wrote
in message news:03DC3017-A427-4D46-9109-351A9886866A@microsoft.com...

"Defect Architect" wrote:

[..] What about
this: class A
{
public:

  A(int)
  {
  }

private:

  A(const A &);
  A &operator=(const A &);
};

class B : public A
{
public:
  B(int) : A(0)
  {
  }
};

B foo()
{
  return 0;
}

void bar()
{
  B b = foo();
}

Does B have an implicit copy constructor? If so, how does it
handle A's private copy constructor? If it works, why can I not
add this line to bar() ?

B b2 = b;

Thanks!

This does not compile with gcc 4.02.

Borland Turbo C++ generates an error:
[C++ Error] Unit1.cpp(34): E2285 Could not find a match for
'B::B(const B&)' on the line B b = foo();

I've not received the answer from Comeau Computing yet, but the
consensus in comp.lang.c++[.moderated] is that it's a bug in Comeau
(and in Visual C++, obviously). The program is ill-formed because
the copy constructor cannot be generated for 'B' and "B b = foo();"
does require for the copy constructor to exist under the "as if the
copy is actually made" rule.

V
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