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From: "m.cencora at gmail dot com" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug ipa/109770] [10/11/12/13/14 Regression] wrong(?) devirtualization
Date: Tue, 09 May 2023 09:34:13 +0000 [thread overview]
Message-ID: <bug-109770-4-Q6sO3ifWId@http.gcc.gnu.org/bugzilla/> (raw)
In-Reply-To: <bug-109770-4@http.gcc.gnu.org/bugzilla/>
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=109770
--- Comment #8 from m.cencora at gmail dot com ---
(In reply to Richard Biener from comment #7)
>
> Ah, interesting. I was looking for an answer whether
>
> new T
>
> may produce anything other than an object with dynamic type T or if there
> are any constraints on the object constructed. In particular C++20 11.10.4
> refered to by 6.7.3 doesn't mention whether re-using the storage is
> permitted for an object under construction. It says usage is limited
> and doesn't explicitely allow re-use so that might mean re-use is not
> allowed.
>
> Note std::launder is C++17 only, the original reporter was using C++98 /
> C++14
>
> Reading C++20, 6.7.3/9, at least suggests that the placement new (this) A
> in the CTOR invokes undefined behavior because the lifetime of B hasn't
> ended (but 6.7.3/1.5 makes this ambiguous - we're re-using the storage here,
> and also we're not talking about an object with automatic storage duration).
6.7.3/9 doesn't apply to your example - this is not an automatic storage
duration.
If 11.10.4 is suppose to be an exhaustive allow-list, then yeah ending the
complete object lifetime during its construction is UB, but I guess it would be
best to get a response from real C++ expert or file a C++ core issue.
next prev parent reply other threads:[~2023-05-09 9:34 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-05-08 13:30 [Bug ipa/109770] New: " rguenth at gcc dot gnu.org
2023-05-08 13:31 ` [Bug ipa/109770] " rguenth at gcc dot gnu.org
2023-05-08 13:34 ` rguenth at gcc dot gnu.org
2023-05-08 17:09 ` rguenth at gcc dot gnu.org
2023-05-08 17:14 ` [Bug ipa/109770] [10/11/12/13 Regression] " rguenth at gcc dot gnu.org
2023-05-08 17:21 ` [Bug ipa/109770] [10/11/12/13/14 " rguenth at gcc dot gnu.org
2023-05-09 8:24 ` m.cencora at gmail dot com
2023-05-09 8:49 ` rguenth at gcc dot gnu.org
2023-05-09 9:34 ` m.cencora at gmail dot com [this message]
2023-05-17 17:07 ` redi at gcc dot gnu.org
2023-07-07 10:45 ` [Bug ipa/109770] [11/12/13/14 " rguenth at gcc dot gnu.org
2024-01-12 10:53 ` rguenth at gcc dot gnu.org
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