[Qt-interest] Qt 4.6.1, Qt JPEG plugin and macdeploy: bus error because it loads two copies of the Qt frameworks

[Marco Molteni]

Hi all,

here is my setup: MacOSX 10.5, Qt 4.6.1 (carbon), project built with  
cmake. I do not play any trick at all in the compilation or linking  
phase.
The code loads some JPEG images, and so it uses the libqjpeg.dylib Qt  
plugin.

The bundle runs correctly as built, with all the references to the Qt  
frameworks resolved to /Library/Frameworks/QtXXX.

The problem comes if I try to prepare the bundle for deployment, using  
macdeployqt.

Running macdeployqt works fine, and it creates correctly the  
Frameworks directory below the bundle directory and also Resources/ 
qt.conf, mapping the plugins to the local, macdeplyqt-created  
directory PlugIns. Running otool -L on the various libraries, and also  
on the plugins seem to give the expected result.

But, when running the bundle prapared by macdeployqt, it gets a bus  
error. The debug output, by setting DYLD_PRINT_LIBRARIES and  
QT_DEBUG_PLUGINS is as follows:

$ DYLD_PRINT_LIBRARIES=1 QT_DEBUG_PLUGINS=1 ./Octopus.app/Contents/ 
MacOS/Octopus 2> q

$ cat q | grep Qt | head -14 | cat -n
      1	dyld: loaded: /Users/mmolteni/src/octopus-hgsvn/qtcreator- 
build/octopus-gui/./Octopus.app/Contents/MacOS/../Frameworks/ 
QtGui.framework/Versions/4/QtGui
      2	dyld: loaded: /Users/mmolteni/src/octopus-hgsvn/qtcreator- 
build/octopus-gui/./Octopus.app/Contents/MacOS/../Frameworks/ 
QtXml.framework/Versions/4/QtXml
      3	dyld: loaded: /Users/mmolteni/src/octopus-hgsvn/qtcreator- 
build/octopus-gui/./Octopus.app/Contents/MacOS/../Frameworks/ 
QtNetwork.framework/Versions/4/QtNetwork
      4	dyld: loaded: /Users/mmolteni/src/octopus-hgsvn/qtcreator- 
build/octopus-gui/./Octopus.app/Contents/MacOS/../Frameworks/ 
QtCore.framework/Versions/4/QtCore
      5	QFactoryLoader::QFactoryLoader() looking at "/Developer/ 
Applications/Qt/plugins/imageformats/libqgif.dylib"
      6	QFactoryLoader::QFactoryLoader() looking at "/Developer/ 
Applications/Qt/plugins/imageformats/libqico.dylib"
      7	QFactoryLoader::QFactoryLoader() looking at "/Developer/ 
Applications/Qt/plugins/imageformats/libqjpeg.dylib"
      8	QFactoryLoader::QFactoryLoader() looking at "/Developer/ 
Applications/Qt/plugins/imageformats/libqmng.dylib"
      9	QFactoryLoader::QFactoryLoader() looking at "/Developer/ 
Applications/Qt/plugins/imageformats/libqsvg.dylib"
     10	QFactoryLoader::QFactoryLoader() looking at "/Developer/ 
Applications/Qt/plugins/imageformats/libqtiff.dylib"
     11	dyld: loaded: /Developer/Applications/Qt/plugins/imageformats/ 
libqjpeg.dylib
     12	dyld: loaded: /Library/Frameworks/QtGui.framework/Versions/4/ 
QtGui
     13	dyld: loaded: /Library/Frameworks/QtCore.framework/Versions/4/ 
QtCore
     14	On Mac OS X, you might be loading two sets of Qt binaries into  
the same process. Check that all plugins are compiled against the  
right Qt binaries. Export DYLD_PRINT_LIBRARIES=1 and check that only  
one set of binaries are being loaded.


So as you can see, lines 1-4 are what I would expect, the linker is  
loading the right frameworks, but then at line 5, Qt for some reasons  
doesn't follow the qt.conf file and instead loads the system-installed  
Qt plugins, that then, at line 12, cause to load a second copy of  
QtGui, and so on.

I spent a lot of time trying to debug this, I would appreciate any  
help before giving up and compiling Qt static from source :-(

thanks
marco