[Pythonmac-SIG] Tiger hand rolled Python 2.4.1: libxml2 oddities

[Bob Ippolito]

On May 5, 2005, at 2:20 PM, Bob Ippolito wrote:

>
> On May 5, 2005, at 12:55 PM, Gary Poster wrote:
>
>
>> Using Python 2.4.1 compiled on Tiger.  This symptom did not occur on
>> Panther.
>>
>> Running my app using one command makes an import of libxml2 succeed:
>> all test pass, including a lot of code that relies on libxml2.
>>
>> Running it with another command makes it fail:
>>
>> *** ImportError: Failure linking new module: /Users/gary/jic/opt/
>> libxml2/lib/python/libxml2mod.so: Symbol not found:
>> _xmlTextReaderByteConsumed
>>    Referenced from: /Users/gary/jic/opt/libxml2/lib/python/
>> libxml2mod.so
>>    Expected in: flat namespace
>>
>> I've put a pdb before the import to examine the two environments.
>> I've checked sys.path, os.environ, and sys.getdlopenflags()
>> (recommended by a coworker) and gotten results that were either
>> identical or that (in the case of sys.path) I munged until they were
>> identical, and still one import works, the other doesn't.
>>
>
> It sounds like libxml2 (or the Python extension) uses the linker
> option flat_namespace .. that's bad.  -flat_namespace has been
> deprecated since 10.2 (maybe earlier) and shouldn't be used for
> anything.  I can't help you though, I don't use libxml2 so I don't
> know the specifics of why its build/link procedure is broken.

More specifically, after looking again, "libxml2mod.so" isn't  
explicitly linking to libxml2 (and may also be using the deprecated - 
flat_namespace)..  Somewhere in your "one command" it's importing  
something that does explicitly link to libxml2, but your "another  
command" does not have that side-effect that band-aids the fact that  
"libxml2mod.so" is linked incorrectly.  The solution to this specific  
problem is to fix whatever builds "libxml2mod.so" so that it links  
against libxml2 (-lxml2, or adding it to the distutils library list,  
etc.).. but I have a feeling that's not the ONLY thing wrong with it.

It "smells" like one of those horribly broken Python extensions that  
uses autoconf instead of distutils.

-bob