Undefined symbol with single threaded python

[Ulrich Seidl]

When using a single threaded python 2.7, and trying to do "from lxml import etree", I get the following error:

lib/python2.7/site-packages/lxml/etree.so: undefined symbol: PyThread_free_lock

Even though lxml was compiled with "python setup.py build --without-threading" and the compile time flag "WITHOUT_THREADING" was set when compiling lxml.etree.c, there are still some symbols left which require threading support in python. Doing a:

nm etree.so | grep -i thread

results in the following output:

         U PyThreadState_GetDict
         U PyThread_free_lock
         U _PyThreadState_Current
000239d0 t __pyx_f_4lxml_5etree_24_ParserDictionaryContext__findThreadParserContext
00054b90 t __pyx_f_4lxml_5etree_24_ParserDictionaryContext__getThreadDict
00054c50 t __pyx_f_4lxml_5etree_24_ParserDictionaryContext_initThreadDictRef
000367a0 t __pyx_f_4lxml_5etree_fixThreadDictNames
00036490 t __pyx_f_4lxml_5etree_fixThreadDictNamesForNode

I would assume that the three undefined *PyThread* symbols should not be in the etree.so library when compiled with "python setup.py build --without-threading".

[scoder (scoder)]

A patch that fixes this would be appreciated.

[Ulrich Seidl (ulrich-seidl)]

I would suggest to extend the if-clause ("if self._lock is not NULL") of the __dealloc__ method of the _ParserContext class with a check for config.ENABLE_THREADING. Same check is already done in __cinit__ method. At least with cython 0.17.4, gcc 4.4.6 & python 2.7.3 this solves the problem for me.

[scoder (scoder)]

https://github.com/lxml/lxml/commit/f2e0f8a898673511794a38350a30353d545baa3a

Thanks!

[scoder (scoder)]

Released in lxml 3.1.0.