On Monday, 22 June 2015 at 10:04:28 UTC, Marc Schütz wrote:
On Monday, 22 June 2015 at 06:38:57 UTC, Andrei Alexandrescu
wrote:
On 6/21/15 11:31 PM, Andrei Alexandrescu wrote:
On 6/21/15 10:25 PM, Walter Bright wrote:
The idea is that fun(5) would be lowered to:
auto tmp = 5;
fun(tmp);
I don't think that lowering is recommended - it prolongs the
lifetime of
the temporary through the end of the caller. But that may be
actually a
good thing.
On second thought - Walter's lowering, which makes the rvalue
last more than strictly necessary, may be the most flexible of
all at the cost of more resource consumption (for types that
define destructors). -- Andrei
Why would that be desirable? Resource consumption is the least
of the problems. It is simply surprising, inconsistent with the
lifetime of other temporaries, and it is unnecessary. Just
lower it to:
{
auto tmp = 5;
fun(tmp);
}
I see now that Andrei already wrote in the PR "creating a named
temporary in a scope immediately enclosing the call". I would
like to add that AFAIK other temporaries live until the end of
the entire statement they appear in, not just for the duration of
the call. In any case, the temporaries involved here should not
behave different from normal temporaries; in particular, they
should have the same lifetime as with pass-by-value.
