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From: "redi at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug libstdc++/108645] Change in behavior, std::accumulate doesn't always work as expected in C++20 builds
Date: Fri, 03 Feb 2023 10:08:11 +0000	[thread overview]
Message-ID: <bug-108645-4-6SCdpTdY0A@http.gcc.gnu.org/bugzilla/> (raw)
In-Reply-To: <bug-108645-4@http.gcc.gnu.org/bugzilla/>

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=108645

--- Comment #5 from Jonathan Wakely <redi at gcc dot gnu.org> ---
(In reply to Jonathan Wakely from comment #3)
> In your example, all your strings fit in the SSO buffer inside the
> std::string object, so the LHS has sufficient capacity for the result.

Actually that's only true until the last step of the algorithm. On the last
step (when appending "example" to "this_is_an_") neither the LHS nor the RHS
has capacity for the result, so a reallocation is needed. But it's true that
the RHS has nothing to steal at any step in the algorithm, so we append to the
LHS and let that reallocate itself if needed.

> And
> there's nothing to steal from the RHS anyway, as it doesn't own any
> allocated memory.

      parent reply	other threads:[~2023-02-03 10:08 UTC|newest]

Thread overview: 6+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2023-02-02 21:00 [Bug libstdc++/108645] New: " eteran at alum dot rit.edu
2023-02-02 21:05 ` [Bug libstdc++/108645] " eteran at alum dot rit.edu
2023-02-03  1:40 ` pinskia at gcc dot gnu.org
2023-02-03  9:32 ` redi at gcc dot gnu.org
2023-02-03 10:01 ` redi at gcc dot gnu.org
2023-02-03 10:08 ` redi at gcc dot gnu.org [this message]

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