I've kind of tracked down the issue - qtcreator doesn't add -g option to CFLAGS when building in debug mode. In fact it doesn't add any optimization options when building in release mode either...

Here's a build line in debug mode:
Qt Code: 
  1. g++ -c -pipe -Wall -W -D_REENTRANT -DQT_GUI_LIB -DQT_CORE_LIB -DQT_SHARED -I/usr/share/qt4/mkspecs/linux-g++ -I. -I/usr/include/qt4/QtCore -I/usr/include/qt4/QtGui -I/usr/include/qt4 -I. -I. -o main.o main.cpp
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ant this is in release mode:
Qt Code: 
  1. g++ -c -pipe -Wall -W -D_REENTRANT -DQT_NO_DEBUG -DQT_GUI_LIB -DQT_CORE_LIB -DQT_SHARED -I/usr/share/qt4/mkspecs/linux-g++ -I. -I/usr/include/qt4/QtCore -I/usr/include/qt4/QtGui -I/usr/include/qt4 -I. -I. -o main.o main.cpp
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The only difference is -DQT_NO_DEBUG.

I clearly remember, that this stuff used to work in the past. What could have happened that broke it?