Re: Lifetime of a temporary bound to a reference
itaj sherman wrote:
I'm not sure what the standard says about a case like this (mainly per
12.2/5):
class B {};
class D1: public B {};
class D2: public B {};
void foo( bool r )
{
B const& a = ( r ? D1() : D2() );
// Does the temporary live here?
}
I'm sorry to annoy you again, but i've just noticed that the issue report
link i gave was discussing the comma operator instead of the conditional
operator (omg, epic fail). It turns out from links in that issue report
that the issue with the conditional operator has been fixed in C++0x by
http://www.open-std.org/jtc1/sc22/wg21/docs/cwg_defects.html#446 . It
provides the "direct reference" i talked about.
Looking at it again, i found an interesting similarity with bit-fields: An
object can be a bit-field, but an expression can be a bit-field likewise.
Like, it's said "the result is of that type and value category and it is a
bit-field if ..." at 5.16/4 in the FCD. If it would omit the addendum, the
expression would potentially refer to a bit-field, but won't be a bit-field
itself. This seems to be exactly like the situation with temporaries. The
lifetime-lengthening subsection refers to the expression property, thus it
doesn't care about lvalues that refer to temporaries, because those lvalues
won't have the "temporary" property be true. But now, i'm just more confused
how these things fit together, really :(
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