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Re: [std-proposals] Relax the restriction on the operand of a single-object delete-expression

From: blacktea hamburger <greenteahamburger_at_[hidden]>
Date: Sun, 2 Oct 2022 13:42:33 +0800
I forgot to say that "behaves right" requires operator new to correspond to
operator delete.

If it corresponds, then the behavior is completely correct, because the
delete expression is equivalent to call destructor + operator delete.

Of course the code could be better:

auto* p = operator new(sizeof(T));
auto* pc = new(p) T;
::delete pc;

This way for any T, the code is correct.

If T definitely does not overload operator new and operator delete, then ::
may not be used. If it's wrong, the behavior is undefined.

The same applies to the original issue.

On Sun, Oct 2, 2022 at 9:29 AM Jason McKesson via Std-Proposals <
std-proposals_at_[hidden]> wrote:

> On Sat, Oct 1, 2022 at 8:51 PM blacktea hamburger via Std-Proposals
> <std-proposals_at_[hidden]> wrote:
> >
> > I'm using "forbid" wrong. It should be "undefined behavior," because
> obviously it can't be checked at compile time. It's better to make it
> well-formed, because unintended but correct behavior is better than
> undefined behavior.
> That changes nothing about my question: why not? Equally importantly,
> how is it "correct behavior"? It's code that is *incoherent.* You
> initialized the object in a way that says something about the
> relationship between the object and its storage, and you destroyed the
> object in a way that says something *different* about the relationship
> between the object and its storage.
> Why is this "correct behavior"? Who is to say what "correct behavior"
> even is if you're not consistent on what you're doing?
> Not to mention the fact that, as Thiago pointed out, it is not even
> "correct behavior" if `T` has an `operator delete` overload. And
> again, IOC can work just fine on such types.
> --
> Std-Proposals mailing list
> Std-Proposals_at_[hidden]
> https://lists.isocpp.org/mailman/listinfo.cgi/std-proposals

Received on 2022-10-02 05:43:03