Debugging initdb breakage

On 10.10.2010 23:38, Dimitri Fontaine wrote:

So I'm beginning to work on the extension support for dump and restore,
and that begins with a new pg_extension catalog. I managed to break
initdb already, of course, but I'm fighting my way out — no luck with
gdb, it won't catch the Assert failure and show me a backtrace. I tried
"set follow-fork-mode child" in gdb, in different systems, to no avail.

Please find attached the detailed initdb.log and the very few items I
needed to obtain:

TRAP: FailedAssertion("!(reln->md_fd[forkNum] == ((void *)0))", File: "md.c", Line: 254)
child process was terminated by signal 6: Abort trap

How to have gdb help me? What's my error, that I guess is obvious? Where
do I read more now in order not to need too much assistance after that?

At least on my system, assertion failure creates a core dump that you
can load in gdb. Make sure you use "ulimit -c unlimited" or similar.

--
Heikki Linnakangas
EnterpriseDB http://www.enterprisedb.com

Dimitri Fontaine <dimitri@2ndQuadrant.fr> writes:

How to have gdb help me? What's my error, that I guess is obvious?

Might have something to do with using the same OID for the catalog
and its index ...

regards, tom lane

Tom Lane <tgl@sss.pgh.pa.us> writes:

Might have something to do with using the same OID for the catalog
and its index ...

Ahah, that's how obvious it was, thank you. I feel ashamed, but at the
same time, thanks to your answer, it now feels like the week-end was a
good preparatory step for opening this week.

Back to producing cores (ulimit -c unlimited),
--
Dimitri Fontaine
http://2ndQuadrant.fr PostgreSQL : Expertise, Formation et Support

Excerpts from Dimitri Fontaine's message of dom oct 10 17:38:01 -0300 2010:

Hi,

So I'm beginning to work on the extension support for dump and restore,
and that begins with a new pg_extension catalog. I managed to break
initdb already, of course, but I'm fighting my way out — no luck with
gdb, it won't catch the Assert failure and show me a backtrace. I tried
"set follow-fork-mode child" in gdb, in different systems, to no avail.

As a note, I've had luck finding bootstrap-time bugs by manually feeding
the bootstrapping commands into bootstrap mode, with a leftover dir from
"initdb --noclean". This has helped a few times that there has been no
PANIC but just a FATAL or ERROR, for example. It's easy to attach GDB
to such a backend.

--
Álvaro Herrera <alvherre@commandprompt.com>
The PostgreSQL Company - Command Prompt, Inc.
PostgreSQL Replication, Consulting, Custom Development, 24x7 support

Alvaro Herrera <alvherre@commandprompt.com> writes:

As a note, I've had luck finding bootstrap-time bugs by manually feeding
the bootstrapping commands into bootstrap mode, with a leftover dir from
"initdb --noclean". This has helped a few times that there has been no
PANIC but just a FATAL or ERROR, for example. It's easy to attach GDB
to such a backend.

Nice tip, thanks!
--
Dimitri Fontaine
http://2ndQuadrant.fr PostgreSQL : Expertise, Formation et Support

On Tue, Oct 12, 2010 at 10:05:57PM +0200, Dimitri Fontaine wrote:

Alvaro Herrera <alvherre@commandprompt.com> writes:

As a note, I've had luck finding bootstrap-time bugs by manually
feeding the bootstrapping commands into bootstrap mode, with a
leftover dir from "initdb --noclean". This has helped a few times
that there has been no PANIC but just a FATAL or ERROR, for
example. It's easy to attach GDB to such a backend.

Nice tip, thanks!

Where should we preserve this, other than the mailing list archives?

Cheers,
David.
--
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Phone: +1 415 235 3778 AIM: dfetter666 Yahoo!: dfetter
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David Fetter wrote:

Where should we preserve this, other than the mailing list archives?

http://wiki.postgresql.org/wiki/Getting_a_stack_trace_of_a_running_PostgreSQL_backend_on_Linux/BSD
has most of the other trivia in this area, so I just added Alvaro's
technique to the bottom of it with a quick intro to add some context.

--
Greg Smith, 2ndQuadrant US greg@2ndQuadrant.com Baltimore, MD
PostgreSQL Training, Services and Support www.2ndQuadrant.us