[Distutils] Dynamic linking on Linux, Mac OS, et al

[Bob Ippolito]

On Jan 5, 2006, at 9:00 PM, Robert Kern wrote:

> Phillip J. Eby wrote:
>> Hi folks.  I just implemented preliminary shared library build  
>> support for
>> setuptools, but I ran into a bit of a snag.  I was operating under  
>> the
>> assumption that you could simply put shared libraries in the  
>> directory
>> alongside the extensions that use them, but in practice it turns  
>> out that
>> this only works on Windows.  On Linux I found that you could only put
>> shared libraries in a directory on LD_LIBRARY_PATH, and I suspect  
>> a similar
>> issue will be found under OS X and other Unixes.
>
> On OS X, the headers of the dylib can be rewritten to point to a  
> specific path.
> IIRC, this can be a relative path. Bob Ippolito's py2app does this  
> kind of
> rewriting for making relocatable .app bundles. I'm sure he'll chime  
> in soon, so
> I'm not entirely sure why I bothered replying myself.

It's actually the extension that needs the rewriting.. but it's good  
to rewrite the dylib also.

It can be a relative path, but only relative to the executable.  You  
can be relative to the bundle on Mac OS X 10.4+, but it really ought  
to just make the path static upon installation and remain backwards  
compatible.  In order to make that bulletproof, the linker flag - 
headerpad_max_install_names should be used.

-bob