[C++-sig] Cross-module inheritance (original) (raw)

David Abrahams dave at boost-consulting.com
Sun Aug 21 17:25:29 CEST 2005

Eric Jardim <ericjardim at gmail.com> writes:

Hi again,

I searched google and discovered that the problem is real. Cross-module inheritance and some other things do not work with boost.python (I don't know why).

It certainly does work; you just have to follow some rules when you build your extensions to make sure their RTTI info is properly shared.

Some old posts show it: http://lists.boost.org/Archives/boost/2001/07/14520.php http://lists.boost.org/Archives/boost/2001/07/14491.php

That was for Boost.Python v1. You are (I hope) using the improved Boost.Python v2

And recent posts show that some guys resolved the problem (partially): http://mail.python.org/pipermail/c++-sig/2005-April/008829.html http://mail.python.org/pipermail/c++-sig/2005-April/008835.html

Doing: import sys, dl sys.setdlopenflags(dl.RTLDNOW|dl.RTLDGLOBAL)

This is the brute-force method. A more delicate and portable approach is to stick the common base class in a shared library that is linked to by all the extension modules that derive from it.

But, I am afraid this is not a portable solution.

1 - Could anyone tell me if, at least, this solution is portable among gcc compilation, even on Windows?

No, the Windows dynamic linking system is different. However, the approach I suggested above works fine.

2 - Does anyone suggest me to use this trick now, or should I stay with the "single-module", and wait for this issue to be solved (is it possible, given boost.python current state?)

There is no "solving it" further; it has nothing to do with the state of Boost.Python. It has to do with the way shared libraries and run-time type information work on your platform.

3 - Is there any other workaround? It looks like SWIG can do it (am I right?) 4 - Should I give up everything? ( hope not ;)

It's a little early for that yet.

-- Dave Abrahams Boost Consulting www.boost-consulting.com

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