[Qgis-developer] Using the Qt*_debug Libraries to Find Bad Qt Connections

[Tom Elwertowski]

Hello all,

I have recently started using the Qt*_debug libraries. One of the things 
these libraries do is report bad connections at runtime. We have several 
connections where either the signal or slot isn't defined and the 
regular libraries don't report this. connect() does return a bool but we 
don't check it.

In order not to confuse readers of our code, we should use the debug 
libraries to monitor connections and either remove one-sided connections 
or else add empty functions on the other side with NYI comments.

On a Mac, the debug libraries can be activated by defining:
export DYLD_IMAGE_SUFFIX=_debug

This has no effect on Ubuntu so I modified line 383 of my working copy 
of acinclude.m4 to be:
QT_LIB="-lQtCore_debug -lQt3Support_debug -lQtGui_debug 
-lQtNetwork_debug -lQtSvg_debug"

If there isn't an automatic way to do this on Linux, perhaps we should 
add a --enable-qtdebug option to configure.


Qt/Mac 4.1.1 warning and workaround:

Don't use the suffix _debug. Setting this suffix will load all debug 
libraries, not just the Qt debug libraries. There are problems in the Qt 
4.1.1 libraries which trigger fatal assertions in the Mac OS debug 
libraries.

Instead, do for each Qt library:
ln -s QtCore_debug $QTDIR/QtCore.framework/Versions/4.0/QtCore_debugqt

Then do:
export DYLD_IMAGE_SUFFIX=_debugqt

This workaround will load the Qt debug libraries without loading the Mac 
OS debug libraries.

Tom