Re: BUG #19547: libpqrcv_create_slot dereferences NULL on a malformed CREATE_REPLICATION_SLOT reply

From: Fujii Masao <masao(dot)fujii(at)gmail(dot)com>
To: Kenny Chen <kennychen851228(at)gmail(dot)com>
Cc: "Hayato Kuroda (Fujitsu)" <kuroda(dot)hayato(at)fujitsu(dot)com>, "1217816127(at)qq(dot)com" <1217816127(at)qq(dot)com>, "pgsql-bugs(at)lists(dot)postgresql(dot)org" <pgsql-bugs(at)lists(dot)postgresql(dot)org>
Subject: Re: BUG #19547: libpqrcv_create_slot dereferences NULL on a malformed CREATE_REPLICATION_SLOT reply
Date: 2026-07-15 14:10:15
Message-ID: CAHGQGwHJQ5f+yRT-E=20b1UaukLN4Sy=rdEFBvrdZhPtxpTP9w@mail.gmail.com
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On Wed, Jul 15, 2026 at 8:51 PM Kenny Chen <kennychen851228(at)gmail(dot)com> wrote:
> Agreed. IDENTIFY_SYSTEM tolerates 3 columns only because older servers (9.3
> and earlier) actually returned 3, whereas CREATE_REPLICATION_SLOT has always
> returned 4, so there is no reason to be lenient here. v2 attached requires 4
> fields, and updates the comment and errdetail accordingly.

Agreed. So,

+ if (PQnfields(res) < 4 || PQntuples(res) != 1)
+ ereport(ERROR,
+ (errcode(ERRCODE_PROTOCOL_VIOLATION),
+ errmsg("invalid response from primary server"),
+ errdetail("Could not create
replication slot \"%s\": got %d rows and %d fields, expected %d rows
and %d or more fields.",
+ slotname,
PQntuples(res), PQnfields(res), 1, 4)));

"PQnfields(res) < 4" should be "PQnfields(res) != 4"?
If so, "or more" in the detail message should be removed as well.

Regards,

--
Fujii Masao

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