Re: compile error about auto_ptr

=?Utf-8?B?R2Vvcmdl?= <>
Mon, 25 Feb 2008 00:38:01 -0800
Thanks Alf!

That said, what I meant was what I wrote, ??12.8/2 of the standard, but
the non-normative note clarifies one of the consequences.

To make sure we are on the same page, do you mean this one?

ISO 14882

A non-template constructor for class X is a copy constructor if its first
parameter is of type X&, const X&,
volatile X& or const volatile X&, and either there are no other parameters
or else all other
parameters have default arguments (8.3.6).106) [Example: X::X(const X&) and
X::X(X&, int=1)
are copy constructors.
class X {
// ...
X(const X&, int = 1);
X a(1); // calls X(int);
X b(a, 0); // calls X(const X&, int);
X c = b; // calls X(const X&, int);
???end example] [Note: all forms of copy constructor may be declared for a
class. [Example:
class X {
// ...
X(const X&);
X(X&); //OK
???end example] ???end note] [Note: if a class X only has a copy constructor
with a parameter of type X&,
an initializer of type const X or volatile X cannot initialize an object of
type (possibly cv-qualified) X.
struct X {
X(); //default constructor
X(X&); //copy constructor with a nonconst parameter
const X cx;
X x = cx; // error ??? X::X(X&) cannot copy cx into x
???end example] ???end note]

Because a template constructor is never a copy constructor, the presence of
such a template does not suppress the implicit declaration
of a copy constructor. Template constructors participate in overload
resolution with other constructors, including copy constructors,
and a template constructor may be used to copy an object if it provides a
better match than other constructors.


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