Re: Question about use of C++ copy constructor

[Howard Hinnant <hhinnant at apple dot com>]

Also see CWG issue 391:

http://www.open-std.org/jtc1/sc22/wg21/docs/cwg_defects.html#391

which will make our behavior non-conforming in C++0X.

-Howard

On Mar 13, 2006, at 4:02 PM, David Fang wrote:

> Hi,
> 	Didn't see a reply yet, so I'll chime in.
>
> The relevant text appears in gcc-3.4's release notes:
> "When binding an rvalue of class type to a reference, the copy  
> constructor
> of the class must be accessible."
>
> PR 12226 seems to be the mother bug related to this (many dupes).
>
> Fang
>
> > foo.cc: In function ¡Ævoid foo(const B&)¡Ç:
> > foo.cc:3: error: ¡ÆB::B(const B&)¡Ç is private
> > foo.cc:13: error: within this context
> >
> > I don't understand why, as I don't see the copy constructor being  
> > used
> > anywhere.  It seems to me this code should create a temporary for the
> > duration of the statement, and pass the temporary as a reference to
> > b.fn.  This code compiles with icc with no errors.
> >
> > What is wrong with this code?
> >
> > class B {
> >  private:
> >   B(const B&);
> >   void operator=(const B&);
> >
> >  public:
> >   B();
> >   void fn(const B &other) const;
> > };
> >
> > void foo (const B& b)
> > {
> >   b.fn(B());
> > }