Re: Clang UndefinedBehaviorSanitize (Postgres14) Detected undefined-behavior - Mailing list pgsql-hackers

From Peter Geoghegan
Subject Re: Clang UndefinedBehaviorSanitize (Postgres14) Detected undefined-behavior
Date
Msg-id CAH2-Wzn8oEs+1NgubAOZzbM4rNOYak87D6cOo6SN8EH1zYiWPQ@mail.gmail.com
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In response to Re: Clang UndefinedBehaviorSanitize (Postgres14) Detected undefined-behavior  (Andres Freund <andres@anarazel.de>)
Responses Re: Clang UndefinedBehaviorSanitize (Postgres14) Detected undefined-behavior  (Andres Freund <andres@anarazel.de>)
Re: Clang UndefinedBehaviorSanitize (Postgres14) Detected undefined-behavior  (Ranier Vilela <ranier.vf@gmail.com>)
List pgsql-hackers
On Mon, Aug 31, 2020 at 11:42 AM Andres Freund <andres@anarazel.de> wrote:
> Unsigned integer overflow is well defined in the standard. So I don't understand what this is purporting to warn
about.

Presumably it's simply warning that the value -4294901760 (i.e. the
result of 3 - 4294901763) cannot be faithfully represented as an
unsigned int. This is true, of course. It's just not relevant.

I'm pretty sure that UBSan does not actually state that this is
undefined behavior. At least Ranier's sample output didn't seem to
indicate it.

-- 
Peter Geoghegan



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