Re: implicit copy/move constructors

From:

=?ISO-8859-1?Q?Daniel_Kr=FCgler?= <daniel.kruegler@googlemail.com>

Newsgroups:

comp.lang.c++.moderated

Date:

Mon, 16 Aug 2010 20:30:21 CST

Message-ID:

<0dd2884b-f7a6-4cca-86d2-b2b56f9bbb55@q22g2000yqm.googlegroups.com>

On 16 Aug., 20:49, Gene Bushuyev <publicfil...@gbresearch.com> wrote:

I've been testing rvalues in gcc 4.5 and VC 2010 and noticed they both
generated implicit copy constructors even though I provided custom
move constructors, which led to some surprises before I found that. Is
that conforming to the latest C++0x? I kind of expected the other ctor
to be suppressed by providing the user defined copy/move ctor.

Its not the fault of the implementations: The rules had been
changed slightly rather recently. According to the most recent
draft a user-declared move-constructor (assignment operator)
prevents an implicitly declared copy-constructor (assignment
operator) and vice versa. Note that an explicitly defaulted
or deleted special member function is also a user-declaration,
e.g.:

struct X {
  X(const X&) = default; // No implicitly declared move-
                         // constructor
  X& operator=(const X&) = delete; // No implicitly declared
                         // move-assignment operator
};

HTH & Greetings from Bremen,

Daniel Kr?gler

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