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Subject: Re: Missed compiler optimization issue in function
 select_rtable_names_for_explain
From: Daniel Gustafsson <daniel@yesql.se>
In-Reply-To: <4162324.1716396813@sss.pgh.pa.us>
Date: Wed, 22 May 2024 20:14:10 +0200
Cc: XChy <xxs_chy@outlook.com>,
 pgsql-general@postgresql.org
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To: Tom Lane <tgl@sss.pgh.pa.us>
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> On 22 May 2024, at 18:53, Tom Lane <tgl@sss.pgh.pa.us> wrote:
>=20
> Daniel Gustafsson <daniel@yesql.se> writes:
>> They are known to be zero, but that's not entirely equivalent though =
is it?
>> NIL is defined as ((List *) NULL) and NULL is typically defined as =
((void *)
>> 0), so sizeof(0) would be the size of an int and sizeof(NULL) would =
be the size
>> of a void pointer.
>=20
> There are other places where we assume that a memset-to-zero will
> produce null pointers, so I don't think that that objection has
> a lot of force.

It wasn't really an objection, but (perhaps a badly worded) an attempt =
to
understand the proposal.

> My real answer is that this is our coding style
> and we are not going to change it: our normal convention is to
> initialize struct fields in declaration order, and that's what
> we're doing here.  If some particular version of some particular
> compiler fails to make an entirely-negligible optimization in
> consequence, that is not something we are going to care about.

+1

--
Daniel Gustafsson