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From: "andysem at mail dot ru" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug libstdc++/98978] Consider packing _M_Engaged in the tail padding of T in optional<>
Date: Fri, 05 Feb 2021 20:44:41 +0000	[thread overview]
Message-ID: <bug-98978-4-C4DJFGcKqE@http.gcc.gnu.org/bugzilla/> (raw)
In-Reply-To: <bug-98978-4@http.gcc.gnu.org/bugzilla/>

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=98978

--- Comment #3 from andysem at mail dot ru ---
(In reply to Jonathan Wakely from comment #1)
> This would be an ABI break, and so not going to happen.

Is there no way to improve standard components implementation? I'd imagine you
could provide the new implementation in the new version inline namespace and
still support the old ABI for backward compatibility.

(In reply to Jonathan Wakely from comment #2)
> If we were going to do this, we could also make std::optional<bool> occupy a
> single byte, using one bit for the value and one for the engaged flag.

This would be more problematic as emplace(), value() and operator*() need to
return T&, which would not be possible.

  parent reply	other threads:[~2021-02-05 20:44 UTC|newest]

Thread overview: 8+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-02-05 17:14 [Bug libstdc++/98978] New: " andysem at mail dot ru
2021-02-05 17:58 ` [Bug libstdc++/98978] " redi at gcc dot gnu.org
2021-02-05 18:00 ` redi at gcc dot gnu.org
2021-02-05 20:44 ` andysem at mail dot ru [this message]
2021-02-06 17:26 ` redi at gcc dot gnu.org
2021-08-31 16:24 ` redi at gcc dot gnu.org
2022-09-07 12:30 ` redi at gcc dot gnu.org
2022-09-18 12:27 ` andysem at mail dot ru

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