On 1/8/23 08:41, Guillaume Racicot via Std-Proposals wrote:
> Be mindful though that a prvalue is different from an xvalue. Copy
> elision and direct initialization cannot happen with calls to std::move,
> whereas it is permitted with prvalue. If you have a source to source
> compiler you will have to take that into account to not break code, and
> you will have to only generate std::move when the expression would be an
> lvalue.

Yeah I can do that as well, and it would convey with the C++ standards
better.

>
> Here's an example of a non-copiable non-movable type passed in parameter
> by value:
>
> void do_thing_with_mutex(std::mutex);
>
> do_thing_with_mutex(std::mutex{});
>
> If you call std::move on that prvalue, the code will be ill-formed since
> the compiler would be forced to call the move constructor.

Thanks for the head's up.

> It may look like details, but those are important details because you
> might accidentally propose things that will break people and hinder
> performance.
>
> Em sáb., 7 de jan. de 2023 16:44, Phil Bouchard via Std-Proposals
> <std-proposals_at_[hidden] <mailto:std-proposals_at_[hidden]>>
> escreveu:
>
>
>
> On 1/7/23 03:35, Peter Olsson via Std-Proposals wrote:
> >> a.foo(move(list<int>{0, 1, 2, 3, 4, 5, 6, 7, 8, 9}));
> >
> >> foo(move(ostream()));
> >
> > Do you realize that using std::move on a temporary like this is
> pretty
> > pointless because it's already an rvalue?
>
> I was referring to the automatic generated code by the source-to-source
> compiler. Whether it's a r-value and l-value, a move() will be
> generated.
>
>
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