| From: | Peter Geoghegan <pg(at)bowt(dot)ie> |
|---|---|
| To: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
| Cc: | Noah Misch <noah(at)leadboat(dot)com>, Alvaro Herrera <alvherre(at)2ndquadrant(dot)com>, Ranier Vilela <ranier(dot)vf(at)gmail(dot)com>, PostgreSQL Hackers <pgsql-hackers(at)lists(dot)postgresql(dot)org> |
| Subject: | Re: Clang UndefinedBehaviorSanitize (Postgres14) Detected undefined-behavior |
| Date: | 2020-09-04 03:01:54 |
| Message-ID: | CAH2-Wz=ye1o6DR+rk6GGVPacTC7di_bByq3pVz20H83MUZ7Rgg@mail.gmail.com |
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| Lists: | pgsql-hackers |
On Thu, Sep 3, 2020 at 7:53 PM Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
> Hm. I would not blame that on -fdelete-null-pointer-checks per se.
> Rather the problem is what we were touching on before: the dubious
> but standard-approved assumption that memcpy's arguments cannot be
> null.
Isn't it both, together? That is, it's the combination of that
assumption alongside -fdelete-null-pointer-checks's actual willingness
to propagate the assumption.
> I'd still leave -fdelete-null-pointer-checks
> enabled, because it can make valid and useful optimizations in
> other cases.
Is there any evidence that that's true? I wouldn't assume that the gcc
people exercised good judgement here.
--
Peter Geoghegan
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