[Python-Dev] Extension module difficulty w/pgen.

Jonathan Riehl jriehl@spaceship.com
Sat, 28 Sep 2002 18:18:55 -0500 (CDT)

> On Fri, 27 Sep 2002, Guido van Rossum wrote:
> > Maybe the problem is that nothing else uses these symbols?  Try
> > sticking dummy references (e.g. an unreachable call) to them in
> > main.c, to see if that makes a difference.  I recall we had to do this
> > for something else that wasn't used by Python itself.
> I tried this just now, but to no avail.  Maybe I am not being thorough
> enough.  If the linker is excluding these symbols because they are not
> used, why would nm seem to say they are there, and why would statically
> linking libpython work (on FreeBSD, anyway)?  Conversely, I seem to
> remember this working on an earlier, but abandoned attempt I made on a
> Linux box.
It turns out I wasn't being thorough enough.  I used nm on my python
build, and didn't see the symbols there.  I moved the dummy calls to a
global function in python.c and only then were the symbols linked into the

Keeping a dummy function in one of the core modules doesn't seem like a
terribly elegant solution, even if it allows me to keep developing the
pgen module.  What would you suggest be done to ensure that statically
linked builds link those symbols?  I would assume that since the required
symbols *are* in libpython (per my modifications to Makefile.pre.in),
building a python using dynamic libraries would allow the extension module
to "see" those symbols.

You had mentioned doing something like this before.  Is there some linkage
graveyard where I can bury calls to these symbols in order to ensure they
are linked?  Or are some of those fancy API macros used to ensure linkage
(perhaps by API functions that are utilities for extension writers and not
needed by the python core)?