From: David Abrahams (dave_at_[hidden])
Date: 2004-02-10 09:52:06
Anthony Williams <anthony.williamsNOSPAM_at_[hidden]> writes:
>> I don't see any problem here. There's no problem getting the rvalue
>> out of source(), or sink(source()) would fail. Furthermore, no
>> compiler I've ever seen will actually make the allowed temporary in
>> that case.
>
> How about
>
> struct X{};
>
> struct Y
> {
> std::string s;
> X x;
> std::vector<int> v;
> };
>
> Y ySource();
>
> const X& x=ySource().x;
>
> This strikes me as more likely to cause a copy than a straight-forward binding
> from an X temporary.
I think the actual problem is one of either interpretation of 8.5.3/5
or overspecification in that very paragraph. If, instead of saying,
"A temporary of type ``cv1 T2'' [sic] is created, and a constructor
is called to copy the entire rvalue object into the temporary. The
reference is bound to the temporary or to a sub-object within the
temporary"
It said:
"A temporary of type ``cv1 T2'' [sic] is constructed using direct
initialization from the rvalue object. The reference is bound to
the temporary or to a sub-object within the temporary"
we'd be home free.
-- Dave Abrahams Boost Consulting www.boost-consulting.com