[Pythonmac-SIG] py2app and PyQt: QT plugins cause loading multiple QT library versions

[Christian Tismer]

Howdy,

On 31.05.12 21:46, Michael McCracken wrote:
> New user, so new thread, in reference to "(PyQt and py2app) Gui starts
> in IDLE but not as app".
>
> This happens when Qt loads image plugins from the
> system location (likely set during Qt's configure), which
> then load the system Qt.
>
> The problem and a workaround are described here:
> http://lists.trolltech.com/qt-interest/2008-09/thread00258-0.html
>
> py2app's PyQt sample doesn't exercise enough of Qt to hit this problem.
> I'm not sure exactly what part of Qt you'd need to trigger it, but
> I guess the Color Picker might work.
>
> The quick way, if you know you don't need these plugins, is to
> create an empty qt.conf file at MyApp.app/Contents/Resources/qt.conf.
>
...

I've hit a similar problem when trying to build a stand-alone pyside.
Starting with a modified setup.py (not yet ready), I created a working
pyside for virtualenv.
The missing part was support for 'setup.py --standalone', so I found
macholib which does a great job in creating the missing bits.

I simply used a few lines of Python to try out if macholib works for me,
like so:

> from macholib.MachOStandalone import MachOStandalone
> from macholib.util import strip_files
> path='/Users/tismer/src/daniel/pydica/lib/python2.7/site-packages/PySide'
> files = MachOStandalone(path).run(contents='@rpath/Contents')

This works great so far, but the generated pyside complains about 
duplicate libraries.
When I uninstall Qt, it does not find its image plugins.

I guess there is a bug somewhere, which causes the following observation:

$ otool -L /usr/local/Cellar/qt/4.8.3/plugins/imageformats/libqtiff.dylib
/usr/local/Cellar/qt/4.8.3/plugins/imageformats/libqtiff.dylib:
     libqtiff.dylib (compatibility version 0.0.0, current version 0.0.0)
/usr/local/Cellar/qt/4.8.3/lib/QtGui.framework/Versions/4/QtGui 
(compatibility version 4.8.0, current version 4.8.3)
/usr/local/Cellar/qt/4.8.3/lib/QtCore.framework/Versions/4/QtCore 
(compatibility version 4.8.0, current version 4.8.3)
     /usr/lib/libz.1.dylib (compatibility version 1.0.0, current version 
1.2.5)
     /usr/lib/libstdc++.6.dylib (compatibility version 7.0.0, current 
version 56.0.0)
     /usr/lib/libSystem.B.dylib (compatibility version 1.0.0, current 
version 169.3.0)
     /usr/lib/libgcc_s.1.dylib (compatibility version 1.0.0, current 
version 1669.0.0)

$ otool -L 
/Users/tismer/src/daniel/pydica/lib/python2.7/site-packages/PySide/plugins/imageformats/libqtiff.dylib 

/Users/tismer/src/daniel/pydica/lib/python2.7/site-packages/PySide/plugins/imageformats/libqtiff.dylib:
     @rpath/Contents/mageformats/libqtiff.dylib (compatibility version 
0.0.0, current version 0.0.0)
@rpath/Contents/Frameworks/QtGui.framework/Versions/4/QtGui 
(compatibility version 4.8.0, current version 4.8.3)
@rpath/Contents/Frameworks/QtCore.framework/Versions/4/QtCore 
(compatibility version 4.8.0, current version 4.8.3)
     /usr/lib/libz.1.dylib (compatibility version 1.0.0, current version 
1.2.5)
     /usr/lib/libstdc++.6.dylib (compatibility version 7.0.0, current 
version 56.0.0)
     /usr/lib/libSystem.B.dylib (compatibility version 1.0.0, current 
version 169.3.0)
     /usr/lib/libgcc_s.1.dylib (compatibility version 1.0.0, current 
version 1669.0.0)

The problem might be this line:
@rpath/Contents/mageformats/libqtiff.dylib

The "i" from "imageformats" is missing!

This _might_ be related to the unusual case that "libqtiff" has no path 
at all, or something else
is funny, and we end up with a name that will not be found at all.
Then the loader finds the plugin in the installed Qt, which causes it to 
load everything
again from there.

Is that a possible explaining?
I just found that and had not the time to debug it thoroughly.

Cheers - Chris

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