Hi all, 

while building pyside-shiboken from git in preparation for the future Debian
packages, I felt over the issue that (for now), QtGui and QtNetwork modules are
linked to the corresponding QtCore.so through compilation.

That means that the dynamic library linker would have to look into
/usr/path_where_I_put_compiled_Python_modules_with_specific_python_version/PySide/
to find QtCore.so, which is 'obviously' non-standard.

When I do a $ python -c "import PySide.QtNetwork", it fails because the dynamic
linker fails to find QtCore.so.

This is an abstract from a discussion we had in #debian-python about this
issue:

<OdyX> Is there any ldd specialist here ? I have big trouble understanding what
I am supposed to do with PySide.
<OdyX> For the short story: Pyside(-shiboken, non released, actually building
from git) build several modules, mimicking the Qt scheme.
<OdyX> I built all the libs successfully, even with several versions per python
version. 
<OdyX> The issue arises when I build the dependent modules.
<OdyX> e.g. QtNetwork.so (in /usr/lib/pyshared/python2.6/PySide/) needs
QtCore.so (in the same directory)
<OdyX> ldd fails to find it and I can't do a python -c "import
PySide.QtNetwork"
<OdyX> it works if I do a python -c "import PySide.QtCore ;import
PySide.QtNetwork"
<OdyX> I want to ship QtCore.so and QtNetwork.so in different packages (so
python-pyside.qtnetwork should depend on python-pyside.qtcore)
<OdyX> How can I "tell" QtNetwork.so to seek QtCore.so in the same directory ?
<OdyX> do I have to write the .symbols files ?
<jwilk> OdyX: Nope, nothing to do with that.
<OdyX> (I was planning to do so, but waiting on #563752 )
<OdyX> jwilk: from what I understood, dpkg-shlibdeps looks for the dependency,
but fails to find it
<OdyX> http://paste.debian.net/60237/ <- that's what happens with LD_DEBUG=libs
ldd /usr…/QtNetwork.so
<OdyX> can I somehow encode a LD_PRELOAD_PATH in QtNetwork.so ?
<jwilk> OdyX: Kind of, using rpath, but I don't think it's the correct
solution.
<jwilk> OdyX: Do you have build logs somewhere?
<OdyX> I disable rpath on purpose (lintian warning, …)
<Np237> OdyX: the upstream packaging is broken. You can’t expect to have
symbols from another library just because it’s in the same directory.
<Np237> And RPATH would be a solution, but it is not meant for such cases.
<OdyX> Np237: that was my guess… 
<Np237> The correct solution is to split the symbols needed by several modules
in a library, put the library in a private directory (/usr/lib/pyside) and to
use RPATH with this directory.
<Np237> And you’ll see in this case that lintian won’t complain about the
RPATH.
<OdyX> they already have a libpyside (probably for that purpose)
<OdyX>
http://alioth.debian.org/~odyx-guest/packages/pyside/pyside-shiboken_0.2.3+git20100217+fb265bc-1_amd64.build.bz2
<- buildlog
<OdyX> and is there no way to make the call to import PySide.QtNetwork trigger
an import PySide.QtCore before ?
<Np237> OdyX: you can move QtNetwork.so to _QtNetwork.so and make a
QtNetwork.py that does all that’s needed.
<Np237> i.e. import QtCore, from _QtNetwork import *
<OdyX> huh. Ugly
<POX> or you can import QtCore in pyside/__init__.py (IIRC, QtCore is used in
all pyside.* modules)
<Np237> POX: that won’t work for those who just import pyside.QtNetwork, will
it?
<POX> it should, IIRC

I may highlight the following sentences: 

<Np237> OdyX: the upstream packaging is broken. You can’t expect to have
symbols from another library just because it’s in the same directory.
<Np237> The correct solution is to split the symbols needed by several modules
in a library, put the library in a private directory (/usr/lib/pyside) and to
use RPATH with this directory.

And there is a libpyside…

I don't know what would be the proper way to handle this, but my feeling is
clearly that the actual one is wrong.

Thanks in advance and best regards, 

OdyX