[Distutils] linking modules to a shared library

[Bob Ippolito]

On Oct 4, 2005, at 10:46 AM, Stephen Langer wrote:

>
> On Oct 3, 2005, at 3:15 PM, Bob Ippolito wrote:
>
>
>>
>> On Oct 3, 2005, at 10:56 AM, Stephen Langer wrote:
>>
>>
>>
>>>>> Is it possible to create libBase portably with distutils?  It's
>>>>> possible to do it on Linux by  subclassing build_ext.build_ext and
>>>>> explicitly using self.compiler.compile() and
>>>>> self.compiler.link_shared_lib() to build the shared library before
>>>>> calling build_ext.build_ext.build_extensions().  But the same  
>>>>> thing
>>>>> on Mac OS X only creates libBase.so, whereas I need it to create
>>>>> libBase.dylib.
>>>>>
>>>>>
>>>>>
>>>>>
>>>>
>>>> I don't know if this is possible, although I'd guess it is not.
>>>>
>>>>
>>>>
>>>
>>> That's too bad.  Is there a reason for it?  I'd volunteer to work on
>>> modifying distutils so that it can build a .dylib, but I am not an
>>> expert on library formats.  I don't really know the difference
>>> between a .so and a .dylib, except that one of them works and the
>>> other doesn't.  Can someone point me in the direction of a good
>>> reference on the topic?
>>>
>>>
>>
>> The most portable way is to not build a libBase at all.  Build a
>> Python extension that has all the functionality from libBase
>> available in it as a data structure with function pointers, and get
>> a reference to that from everything that depends on libBase
>> functionality.  Take a look at what Numeric's C API does, for  
>> example.
>>
>
> Will such a scheme allow me to define a C++ base class in one module,
> and have other modules define derived classes?  I want users to be
> able to define derived classes without having to recompile the whole
> program.  I also want to be able to choose which parts of the program
> are loaded, so the base classes and some of the derived classes will
> be in one library, but other derived classes will be separate.

I don't know enough about C++ implementation details to answer that..  
try it and see if it works.  It would definitely work for anything C  
or Objective-C based, but C++ is crazy so I don't know.

-bob