Thread: ECPG Segfaulting on EXEC SQL connect

ECPG Segfaulting on EXEC SQL connect

From

"John Smith"

Date:

31 December 2004, 05:54:47

Hello,

I'm trying to convert a series of C programs written originally using Informix ESQL to use Postgres' ECPG.

All of my test programs written from scratch seem to work ok, and I can now precompile, compile and link without error, but when I actually run the program, I get a segfault. This appears to be in the code called by EXEC SQL CONNECT... as evidenced below (output from gdb):

Program received signal SIGSEGV, Segmentation fault.
0x08053640 in error_message ()
(gdb) up
#1 0x4005b95a in _init () from /usr/lib/libpq.so.3
(gdb) up
#2 0x4005ba8f in _init () from /usr/lib/libpq.so.3
(gdb) up
#3 0x4005c35d in fe_getauthname () from /usr/lib/libpq.so.3
(gdb) up
#4 0x4005ed2d in pqPacketSend () from /usr/lib/libpq.so.3
(gdb) up
#5 0x4005c44c in PQconnectStart () from /usr/lib/libpq.so.3
(gdb) up
#6 0x4005c90a in PQsetdbLogin () from /usr/lib/libpq.so.3
(gdb) up
#7 0x4003bf7f in ECPGconnect () from /usr/lib/libecpg.so.4
(gdb) up
#8 0x0804ed15 in cgiMain () at register_customer.pgc:575
575 EXEC SQL connect to pdev_changename;
(gdb)

The database is called pdev_changename, and that same connect statement has worked in another test program.

I'm precompiling using

ecpg -t -C INFORMIX register_customer.pgc -o register_customer.c

and compling with

gcc -g register_customer.c <<some .o and .a files>> -o register_customer.cgi \

-I/usr/include/pgsql -I/usr/include/pgsql/informix -lecpg -lecpg_compat -L/usr/lib/pgsql

I'm using Postgres 8.0.0rc1 on Redhat 9 (kernel 2.4.20-31.9). The same thing happens on fedora core 3, and using Postgres 7.4.6-1.FC3-1.

The ability to define variables of type "timestamp" etc. is so useful, so I really want to keep using "-C INFORMIX" if I can.

Can anyone help shed any light on this?

Thanks,

John

john(at)roundel(dot)net

Re: ECPG Segfaulting on EXEC SQL connect

From

Michael Meskes

Date:

01 January 2005, 18:23:16

On Tue, Dec 28, 2004 at 10:16:04PM -0000, John Smith wrote:
> I'm trying to convert a series of C programs written originally using
> Informix ESQL to use Postgres' ECPG.
> ...
> 575             EXEC SQL connect to pdev_changename;
> ...
> I'm using Postgres 8.0.0rc1 on Redhat 9 (kernel 2.4.20-31.9). The same thing
> happens on fedora core 3, and using Postgres 7.4.6-1.FC3-1.

Could you please try rc3? I did fix some segfaults in the connect
statement. However, I'm not sure you hit the same bug,
actually I expect it to be a different one.

> The ability to define variables of type "timestamp" etc. is so useful, so I
> really want to keep using "-C INFORMIX" if I can.

You can use the datatypes without informix mode. You just have to
include the pgtypes_*.h header files yourself.

> Can anyone help shed any light on this?

I will try if you could send me an example to reproduce the problem. As
you said it does not happen on a small self written test case. Maybe you
can send me one of your source files stripped down to just connect.

Michael
--
Michael Meskes
Email: Michael at Fam-Meskes dot De
ICQ: 179140304, AIM/Yahoo: michaelmeskes, Jabber: meskes@jabber.org
Go SF 49ers! Go Rhein Fire! Use Debian GNU/Linux! Use PostgreSQL!

Re: ECPG Segfaulting on EXEC SQL connect

From

"John Smith"

Date:

02 January 2005, 02:36:47

Hi Michael,

I'll try and get a nice small pared-down source for you to play with that
demonstrates the problem. Once I get that, I could certainly try rc3,
although I was hoping to wait for the RPM...

John.

-----Original Message-----
From: Michael Meskes [mailto:meskes@postgresql.org]
Sent: 01 January 2005 15:08
To: John Smith
Cc: pgsql-general@postgresql.org
Subject: Re: [GENERAL] ECPG Segfaulting on EXEC SQL connect

On Tue, Dec 28, 2004 at 10:16:04PM -0000, John Smith wrote:
> I'm trying to convert a series of C programs written originally using
> Informix ESQL to use Postgres' ECPG.
> ...
> 575             EXEC SQL connect to pdev_changename;
> ...
> I'm using Postgres 8.0.0rc1 on Redhat 9 (kernel 2.4.20-31.9). The same
> thing happens on fedora core 3, and using Postgres 7.4.6-1.FC3-1.

Could you please try rc3? I did fix some segfaults in the connect statement.
However, I'm not sure you hit the same bug, actually I expect it to be a
different one.

> The ability to define variables of type "timestamp" etc. is so useful,
> so I really want to keep using "-C INFORMIX" if I can.

You can use the datatypes without informix mode. You just have to include
the pgtypes_*.h header files yourself.

> Can anyone help shed any light on this?

I will try if you could send me an example to reproduce the problem. As you
said it does not happen on a small self written test case. Maybe you can
send me one of your source files stripped down to just connect.

Michael
--
Michael Meskes
Email: Michael at Fam-Meskes dot De
ICQ: 179140304, AIM/Yahoo: michaelmeskes, Jabber: meskes@jabber.org Go SF
49ers! Go Rhein Fire! Use Debian GNU/Linux! Use PostgreSQL!

Re: ECPG Segfaulting on EXEC SQL connect

From

Hans-Michael Stahl

Date:

18 January 2005, 21:25:12

Michael Meskes wrote the following on 01.01.2005 16:08:

> On Tue, Dec 28, 2004 at 10:16:04PM -0000, John Smith wrote:
>
>>I'm trying to convert a series of C programs written originally using
>>Informix ESQL to use Postgres' ECPG.
>>...
>>575             EXEC SQL connect to pdev_changename;
>>...
>>I'm using Postgres 8.0.0rc1 on Redhat 9 (kernel 2.4.20-31.9). The same thing
>>happens on fedora core 3, and using Postgres 7.4.6-1.FC3-1.

This also happens with Postgresql 7.4. under SUSE Linux 9.1 (kernel
2.6.4-52)  The last version for which embedded SQL worked well for me
was 7.3. The same source which worked fine under 7.3 for many months
stopped working with my switch to 7.4.2. :-(

And it not only happens during connect, but also during a select. It is
very difficult to debug, since often the stack is destroyed and a
backtrace in gdb does not work.  From what I can see it is always
related to calls of malloc/free/realloc issued by libpq.

--
With kind regards | Mit freundlichen Gruessen
Hans-Michael Stahl
Condat AG
Alt-Moabit 91d | 10559 Berlin | Germany | Old Europe
tel: +49.30.3949-1155 | fax: +49.30.3949-2221155
http://www.condat.de/

Re: ECPG Segfaulting on EXEC SQL connect

From

Michael Meskes

Date:

19 January 2005, 13:16:31

On Tue, Jan 18, 2005 at 05:49:05PM +0100, Hans-Michael Stahl wrote:
> This also happens with Postgresql 7.4. under SUSE Linux 9.1 (kernel
> 2.6.4-52)  The last version for which embedded SQL worked well for me
> was 7.3. The same source which worked fine under 7.3 for many months
> stopped working with my switch to 7.4.2. :-(

Interesting.

> And it not only happens during connect, but also during a select. It is
> very difficult to debug, since often the stack is destroyed and a
> backtrace in gdb does not work.  From what I can see it is always
> related to calls of malloc/free/realloc issued by libpq.

I would be happy to help debugging this. But up to now I didn't even
know about this problem. Could you please send me a test case so I can
reproduce this? Also did you try using 8.0?

Michael
--
Michael Meskes
Email: Michael at Fam-Meskes dot De
ICQ: 179140304, AIM/Yahoo: michaelmeskes, Jabber: meskes@jabber.org
Go SF 49ers! Go Rhein Fire! Use Debian GNU/Linux! Use PostgreSQL!

Re: ECPG Segfaulting on EXEC SQL connect

From

Hans-Michael Stahl

Date:

19 January 2005, 20:35:09

Michael Meskes wrote the following on 19.01.2005 11:16:


> I would be happy to help debugging this. But up to now I didn't even
> know about this problem. Could you please send me a test case so I can
> reproduce this?

It is from a very large production example. I have to work a bit to trim
this down to a small example.  I'llt try to provide an example. I now
also remember that the problem *only* occurs with dynamically prepared
statements with cursors, static statements with cursors work w/o problems.

> Also did you try using 8.0?

No, When I encountered the problem I switched back to Informix.

 > Go SF 49ers!

What's that?

 > Go Rhein Fire!

And that?

 > Use Debian GNU/Linux!

I Use Gentoo and SuSE.

 > Use PostgreSQL!

Yes, when Embedded SQL works again :-)



--
With kind regards | Mit freundlichen Gruessen
Hans-Michael Stahl
Condat AG
Alt-Moabit 91d | 10559 Berlin | Germany | Old Europe
tel: +49.30.3949-1155 | fax: +49.30.3949-2221155
http://www.condat.de/

Re: ECPG Segfaulting on EXEC SQL connect

From

Michael Meskes

Date:

20 January 2005, 11:07:43

On Wed, Jan 19, 2005 at 06:07:24PM +0100, Hans-Michael Stahl wrote:
> It is from a very large production example. I have to work a bit to trim
> this down to a small example.  I'llt try to provide an example. I now
> also remember that the problem *only* occurs with dynamically prepared
> statements with cursors, static statements with cursors work w/o problems.

Okay, please let me know when you have a test case. I'd surely like to
fix that. :-)

> > Go SF 49ers!
>
> What's that?

My favourite NFL team, that's professional american style football in the US.

> > Go Rhein Fire!
>
> And that?

My favourite and local NFLE team, that's professional (more or less)
american style football in Europe.

> > Use PostgreSQL!
>
> Yes, when Embedded SQL works again :-)

Okay, let's work on that one. :-)

Michael
--
Michael Meskes
Email: Michael at Fam-Meskes dot De
ICQ: 179140304, AIM/Yahoo: michaelmeskes, Jabber: meskes@jabber.org
Go SF 49ers! Go Rhein Fire! Use Debian GNU/Linux! Use PostgreSQL!