Date: Fri, 28 Jul 2006 00:05:06 -0400
From: Daniel CAUNE <d.caune@free.fr>
Subject: Re: [SQL] PostgreSQL server terminated by signal 11
In-reply-to: <20060727194921.d6389185.darcy@druid.net>
To: "'D'Arcy J.M. Cain'" <darcy@druid.net>,
	'Daniel Caune' <daniel.caune@ubisoft.com>
Cc: tgl@sss.pgh.pa.us, pgsql-admin@postgresql.org, pgsql-sql@postgresql.org
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> -----Message d'origine-----
> De : pgsql-sql-owner@postgresql.org =
[mailto:pgsql-sql-owner@postgresql.org]
> De la part de D'Arcy J.M. Cain
> Envoy=C3=A9 : jeudi 27 juillet 2006 19:49
> =C3=80 : Daniel Caune
> Cc : tgl@sss.pgh.pa.us; pgsql-admin@postgresql.org; pgsql-
> sql@postgresql.org
> Objet : Re: [SQL] PostgreSQL server terminated by signal 11
>=20
> On Thu, 27 Jul 2006 19:00:27 -0400
> "Daniel Caune" <daniel.caune@ubisoft.com> wrote:
> > I run the command responsible for creating the index and I entered
> "continue" in gdb for executing the command.  After a while, the =
server
> crashes:
> >
> >   Program received signal SIGSEGV, Segmentation fault.
> >   0x08079e2a in slot_attisnull ()
>=20
> That's a pretty small function.  I don't see much room for error.  =
This
> diff in src/backend/access/common/heaptuple.c seems like the most
> likely place to catch it.
>=20
> RCS file: /cvsroot/pgsql/src/backend/access/common/heaptuple.c,v
> retrieving revision 1.110
> diff -u -p -u -r1.110 heaptuple.c
> --- heaptuple.c 14 Jul 2006 14:52:16 -0000      1.110
> +++ heaptuple.c 27 Jul 2006 23:37:54 -0000
> @@ -1470,8 +1470,13 @@ slot_getsomeattrs(TupleTableSlot *slot,
>  bool
>  slot_attisnull(TupleTableSlot *slot, int attnum)
>  {
> -       HeapTuple       tuple =3D slot->tts_tuple;
> -       TupleDesc       tupleDesc =3D slot->tts_tupleDescriptor;
> +       HeapTuple       tuple;
> +       TupleDesc       tupleDesc;
> +
> +       assert(slot !=3D NULL);
> +
> +       tuple =3D  slot->tts_tuple;
> +       tupleDesc =3D slot->tts_tupleDescriptor;
>=20
>         /*
>          * system attributes are handled by heap_attisnull
>=20
> Of course, you still have to find out what's calling it with slot set
> to NULL if that turns out to be the problem.  It may also be that slot
> is not NULL but set to garbage.  You could also add a notice there.
> Two, in fact.  One to display the address of slot and one to display
> the value of slot->tts_tuple or slot->tts_tupleDescriptor.  If the
> first shows a non NULL value and the second causes your crash that
> tells you that the value of slot is probably trashed before
> calling the function.
>=20

Yes, I was afraid to go that deeper, but it's time! :-))

Actually it seems, from the source code, that a null slot->tts_tuple =
won't lead to a segmentation fault in function slot_attisnull, while =
slot and slot->tts_tupleDescriptor will.  I will trace the function =
trying to discover what goes wrong behind the scene.

> Do this in conjunction with Tom Lane suggestion of "--enable-debug" =
for
> more information.
>=20
OK

--
Daniel