"Rani Sharoni" <rani_sharoni@hotmail.com> writes:
David Abrahams wrote:
I think the text has to account for the possibility that the constructor used might be explicit, doesn't it?
This is true but explicit copy (or copying) constructor is quite useless (unless someone will find a way to abuse it for good purpose).
Maybe it's useless, but it's detectable.
Raoul Gough and I have tried to relax this surprising reference binding limitation (i.e. requires copying constroctor) for the favor of wider range of cases (e.g. private copy constructor). The suggestion basically says that *direct reference binding* is enough for most cases of class rvalue bindings. http://anubis.dkuug.dk/jtc1/sc22/wg21/docs/cwg_active.html#391
IMO your suggestion is fully compliant and EDG has bug that confuses everyone.
I don't have anything else to add to this discussion.
Maybe some more.
Sorry to draw it out, but I don't understand when you say "suggestion" whether you're referring to my suggested text change or the movable class idiom I posted.
The later. For the moveable class Idiom you don't need to revise the standard text since Steve Adamczyk already did that ~7 years ago when he removed the copy constructor requirement.
I wish you could get EDG, Metrowerks, and Microsoft (and others, I'm sure, including Peter Dimov) to agree with you. There appears to be an emerging consensus among implementors that a public non-const copy ctor is needed.
You only encountered a bug in EDG which is also inconsistent:
struct A { // private: template<typename T> A(T const& r) { int const* p = &r; // error if T != int -> error if T == A p = p; }
private: A(A&); };
int f(A const&);
// template constructor is // enough for the "illusive coping" int x = f(A(10)); // compiled fine using EDG and GCC
Making the template *converting* constructor private will trigger access error for both EDG and GCC although they don't actually call it.
That in itself
VC rejected this code and has open bug for this issue.
Again DR #391: <Q> J. Stephen Adamczyk replied that the reason for changing "a copy constructor" to "a constructor" was to allow for member template *converting* constructors.</Q>
In your moveable implementation the converting constructor (i.e. X(ref)) is as good as template converting constructor from overloading pov which makes your code *fully compliant* within the current standard text. Cheers!
Whoa. Is that different from MoJo? And how can I understand what you're saying well enough to convince implementors that I'm right? -- Dave Abrahams Boost Consulting www.boost-consulting.com