Hi,
You have introduced a new concept.
Object lifetime suspension.
But that's not how you defend it.
Let me ask you a couple of questions and try to answer them.
- what are the pre-conditions on a type so it can suspended its lifetime ?
- the post conditions?
- can it be implemented with -fno-exception?
- how it is handled in a multi-threaded environment?
- does it provide any speed advantage over current operations (copy, move)?
- what patterns resembles to it, or leads to it?
And so forth.
-------- Original message --------
From: Frederick Virchanza Gotham via Std-Proposals <std-proposals@lists.isocpp.org>
Date: 10/24/25 4:24 PM (GMT+01:00)
To: std-proposals@lists.isocpp.org
Cc: Frederick Virchanza Gotham <cauldwell.thomas@gmail.com>
Subject: Re: [std-proposals] Replace an object -- but retain old object if new object fails to construct
On Friday, October 24, 2025, Thiago Macieira via Std-Proposals <std-proposals@lists.isocpp.org> wrote:
I think that's an even more important question: how often do we need this
replacement solution whereby the previously-stored object is present if the
new one throws on construction?
Sometimes we at the very least want to be left with a safe-to-destroy object if the construction fails. Something like:
p->~T();
try
{
::new(p) T(5, 6.22);
}
catch(...)
{
std::construct_moved_from_at<T>(p);
}
A few months back on this mailing list, somebody was talking about introducing "std::moved_from" and I think it's a good idea.