Agree with DoA.

Will further rely on the following solution:
SharedMessageT collapse(SharedMessageT &_rsm, const ssize_t _expect = 1)
{
    SharedMessageT::weak_type wt{_rsm};

    _rsm.reset();

    if(wt.use_count() == _expect){
        return wt.lock();
    }
    return SharedMessageT{};
}

maintain a SharedMessageT instance on producer.

and, on consumer use:
if (auto tmp_sm = collapse(sm)) {
   p.set_value(std::move(tmp_sm));
}

Thanks everyone for your valuable feedback.


On Tue, Dec 12, 2023 at 7:16 PM Marcin Jaczewski <
marcinjaczewski86_at_[hidden]> wrote:

> wt., 12 gru 2023 o 18:01 Thiago Macieira <thiago_at_[hidden]> napisał(a):
> >
> > On Tuesday, 12 December 2023 08:56:21 -03 Valentin Palade wrote:
> > > The main requirements behind resurrect are:
> > >
> > > 1. lock free
> > > 2. preserving the control block that was allocated initially for the
> > > object.
> > >
> > > Because of the second idea, we cannot efficiently move away from the
> old
> > > pointer as we'll need to reallocate the control block.
> >
> > Your conclusion does not follow from the facts. Why do you think that
> moving
> > will cause it to reallocate?
> >
> > Yes, as discussed, depending on a race, you could end up freeing a
> block. I
> > wouldn't expect this to be a problem for an optimisation. It's just a
> best
> > effort.
> >
>
> I could argue a bit longer but Lénárd's email makes the proposal DoA.
> Existence of `weak_pointer` makes `resurrect` at best unreliable.
>
> > --
> > Thiago Macieira - thiago (AT) macieira.info - thiago (AT) kde.org
> > Software Architect - Intel DCAI Cloud Engineering
> >
> >
> >
>