Replacing the main function

Hi,

I am trying to embed GNUProlog inside Python. For that I need to embed
prolog inside C as a first step.
It so happens that I am stumbling on a very simple problem:
I get a seg fault when I do Start_Prolog. My code only does Start_Prolog
and nothing more (and I am wrapping it on a different function than main,
as per the manual).
Some of my gcc parameters are:

-L /usr/lib/gprolog -lengine_pl -llinedit /usr/lib/gprolog/obj_begin.o
/usr/lib/gprolog/obj_end.o

I am on Debian 'testing'.

I have the feeling that I am doing quite a trivial mistake (I don't do C
for over a year).

Can somebody suggest a solution? Thanks a lot

Regards,
Tiago