Handling dynamic libraries with Libtool and Ruby on Mac OS X

[Roland Levillain]

Hello,

I'm a happy user of Libtool and Ruby, and I'm using them both in
several projects, together with the Simplified Wrapper and Interface
Generator (SWIG).  Everything works well under GNU/Linux, but things
get a little bit harder on Mac OS X, and I'm posting this message on
the Libtool and Ruby mailing lists to try and get some help from both
communities.  I apologize for the long message, but I prefer to give a
clear explanation.


The situation is as follows: I'm working on a C++ library[1]
(actually, this library is only composed of C++ headers, since it is a
generic library using template classes and functions); this library
dispose of bindings for the its data structures and algorithms for
Python and Ruby, thanks to SWIG.

SWIG creates C++ wrapper code to be compiled as dynamic module(s),
loaded by the target language runtime, either directly (Ruby) or via a
small glue code (Python).  For the sake of portability, I recently
started to use Libtool for the creation of these dynamic modules.  As
neither Python nor Ruby understands Libtool (`.la') libraries, loading
hooks are used[2].  It works perfectly on GNU/Linux: the interpreter
looks for the Libtool library, extract the real name (``dlname'') of
the dynamic module from the `.la' file, and loads it.

Things don't work as easily on Mac OS X, as far as Ruby is concerned.
Under Mac OS X, dynamic modules produced by libtool (using the options
`-avoid-version -module -shared') end with a `.so' extension (as in
GNU/Linux); hence, Libtool libraries have a dlname ending in `.so'.
But on Mac OS X the original `Kernel.require' method of ruby (used to
load dynamic modules into the interpreter) looks for a file ending in
`.bundle'[3] !

My current workaround is to produce a symbolic link `.libs/mod.bundle'
to `.libs/mod.so' for each Libtool module named `mod.la' in the
project.

What do you people from Libtool and Ruby think about the behaviors of
Libtool and Ruby?  Should libtool create `.bundle' files on
Mac OS X/Darwin?  Or should ruby accept to load `.so' files as valid
dynamic modules on this OS?

Thanks in advance for your answers and advice!



P.S. : We created a small project that summarizes this usage of C++,
Libtool, SWIG and Python/Ruby, named after these languages/tools[4].
This experiment was successfully transposed into two project[1][5] to
create Python/Ruby wrappers over C++ code.



Notes: 
[1]   The Olena project, http://olena.lrde.epita.fr

[2]   System hooks for loading Libtool libraries
- in Python: 
http://svn.gnome.org/viewsvn/*checkout*/gnome-python/trunk/pygobject/ltihooks.py?content-type=text%2Fplain
- in Ruby: http://www.lrde.epita.fr/~levill_r/olena/ltrequire.rb

[3]   Or `.rb', but they don't relate to dynamic modules.

[4]   
http://www.lrde.epita.fr/~levill_r/c++-libtool-swig-python/c++-libtool-swig-python-0.01a.tar.gz

[5]   The Tiger project, http://tiger.lrde.epita.fr


-- 
Roland Levillain
LRDE - http://www.lrde.epita.fr