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

Hi Fujii,

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

Right, CREATE_REPLICATION_SLOT always returns exactly 4 columns, so != 4 is
more accurate.  v3 attached uses != 4 and drops "or more" from the errdetail.

Regards,
Kenny

Fujii Masao  於 2026年7月15日週三 下午10:10寫道：
>
> On Wed, Jul 15, 2026 at 8:51 PM Kenny Chen  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