Обсуждение: Debugging custom type libraries

Hi,

I'm writing a custom type, with the associated functions (type_in,
type_out, etc) written in C, in an external shared library that Postgres
loads at runtime. I was wondering what the best way of debugging these
functions is... I can start postgres through gdb, but can't figure out
how to debug the dynamically loaded functions, or break when they are
executed. I've done my best to find the answer, but have unfortunately
failed.

Any help is much appreciated.

Many thanks,
Will.

On Wed, Feb 18, 2009 at 06:05:43PM +0000, Will Harrower wrote:
> I'm writing a custom type, with the associated functions (type_in,
> type_out, etc) written in C, in an external shared library that Postgres
> loads at runtime. I was wondering what the best way of debugging these
> functions is... I can start postgres through gdb, but can't figure out
> how to debug the dynamically loaded functions, or break when they are
> executed. I've done my best to find the answer, but have unfortunately
> failed.

First step, you must connect with psql and then attach gdb to the
running process (there's a function to get the pid of your backend).
Next, you can use "LOAD foo" in psql to trigger the loading of your
module, gdb should then be able to see it (assuming you have debug
symbols everywhere).

Setting breakpoints should then be easy.

Have a nice day,
--
Martijn van Oosterhout   <kleptog@svana.org>   http://svana.org/kleptog/
> Please line up in a tree and maintain the heap invariant while
> boarding. Thank you for flying nlogn airlines.

Martijn van Oosterhout <kleptog@svana.org> writes:
> First step, you must connect with psql and then attach gdb to the
> running process (there's a function to get the pid of your backend).
> Next, you can use "LOAD foo" in psql to trigger the loading of your
> module, gdb should then be able to see it (assuming you have debug
> symbols everywhere).

On some platforms it's necessary to do the LOAD first (before attaching
with gdb).  Experiment...

            regards, tom lane