[PyKDE] PyQt - undefined symbol

Jim Bublitz jbublitz at nwinternet.com
Sun Apr 20 01:46:01 BST 2003

On 19-Apr-03 Erik Dahlgren wrote:
> I looked a little closer at the nm output of libpython2.2.a and
> found
>          U PyUnicodeUCS2_FromUnicode
> 00000440 T PyUnicodeUCS2_FromUnicode
>          U PyUnicodeUCS2_FromUnicode
> So it is defined. Any idea why libqtcmodule.so can't find it
> then?

I got this whole thing off on a wrong tangent in some respects.
There are basically 4 things that relate to the UCS2/UCS4
distinction: python (the executable), libpython.a, Python.h and
libqtcmodule.so. libpython.a is actually unimportant in most
respects. libqtcmodule.so gets its symbols via Python.h; the
python executable gets it symbols from the Python source files when
compiled, so if Python.h is not from the same set of source files
as python itself, you'll have a mismatch.

My best guess is that RH has two packages: python*.rpm and
python-devel*.rpm. The python executable is probably in the first,
and libpython and Python.h are in the second. If you upgrade one
but not the other, you'd have a mismatch (or if RH built the two
packages inconsistenly it'd be the same).

When you *build* PyQt, it looks for Python symbols in Python.h.
When you *import* PyQt, PyQt tries to resolve the Python symbols
from the interpreter's set of symbols, and in this case fails
because they're a different set.

My mistake (one of several) was to have you treat libpython.a as if
it were a .so file loaded by python - it's not. There is the
equivalent of libpython.a statically linked into the interpreter,
but it may not be the same libpython.a that you can run nm on.
There isn't any way to tell for sure, because your python has its
symbols stripped. All we established is that libpython.a and
Python.h are consistent, which is meaningless in this case.

The two possible solutions are: a) find a python-devel*.rpm package
that matches your python*.rpm package; b) get a complete source
package (eg from python.org) which includes a consistent set of all
components and compile it on your machine. The tarball from
python.org will contain all the components that the two rpms would
contain (and maybe more if RH does a python-devel-doc*.rpm  pkg
too). You'll need to rebuild sip and PyQt from scratch too, so they
no longer contain the inconsistent symbols. Be sure to get Python
2.2.x and *not* 2.3.

Sorry for the mixup - it's the first time I've seen this happen.


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