qt creator - breakpoints don't work

[pmitas]

Hi,

I'm having problems with debugging stuff in qt creator.

I write a simple test app:

int main(int argc, char** argv)
{
	QApplication app(argc, argv);
	QLabel* lol = new QLabel("test");
	lol->show();
	return app.exec();
}

int main(int argc, char** argv)
{
	QApplication app(argc, argv);
	QLabel* lol = new QLabel("test");
	lol->show();
	return app.exec();
}

To copy to clipboard, switch view to plain text mode 

Then I set a breakpoint on any of the lines (or even on all lines) and run the debugger. It skips right through all the breakpoints and enters the main loop. If I then pause the execution and look at the stack trace, it shows the main function is at line 0 and is grayed out, like this: http://i.imgur.com/3EZ3g.png . Double clicking it takes me to the assembly view.

What's going on?

[wysota]

Hard to say without any additional info. You may look at the output from Creator to see if there aren't any warnings related to the debugger.

[pmitas]

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:

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

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

To copy to clipboard, switch view to plain text mode 

ant this is in release mode:

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

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

To copy to clipboard, switch view to plain text mode 

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?

[tbscope]

As a side note, and one I did encounter.
Do not use-o optimisation and -g dwarf information at the same time.

Some breakpoints will fail because the code is optimised.
A debugger making use of the dwarf information will not report the correct line numbers. It will report line numbers of the optimised code.

[pmitas]

Oddly, I rebuilt qt-core (I'm on Gentoo) without optimized-qmake and it started including -g in debug mode, but still is not doing any optimizations in release mode.

I did some snooping around and found the file /usr/share/qt4/mkspecs/common/g++.conf. There I found the lines:

QMAKE_CFLAGS_RELEASE    +=
QMAKE_CFLAGS_DEBUG      += -g

QMAKE_CFLAGS_RELEASE    +=
QMAKE_CFLAGS_DEBUG      += -g

To copy to clipboard, switch view to plain text mode 

Should the first line be empty?

[tbscope]

Did you recently change /etc/make.conf ?
On my system it contains the CXX_FLAGS (or something like that) environment variable.

Edit: note that optimisation isn't always wanted, so you should set the level yourself.

[pmitas]

No, I didn't change /etc/make.conf C(XX)FLAGS lately. It's set to:

CFLAGS="-O2 -march=core2 -msse3 -mssse3 -msse4.1 -pipe -g"
CXXFLAGS="${CFLAGS}"

CFLAGS="-O2 -march=core2 -msse3 -mssse3 -msse4.1 -pipe -g"
CXXFLAGS="${CFLAGS}"

To copy to clipboard, switch view to plain text mode 

I also remember, that in the past the release mode used some or all of these flags.

[wysota]

I don't think qmake takes /etc/make.conf into consideration when generating the Makefile. It should work solely based upon $QTDIR/mkspecs/*.

[pmitas]

Well then, should the QMAKE_CFLAGS_RELEASE variable be empty?

[wysota]

I think you should care more about QMAKE_CXXFLAGS and family.

[pmitas]

I think you should care more about QMAKE_CXXFLAGS and family.

This one's set to just "-pipe".

[wysota]

What about QMAKE_CXXFLAGS_DEBUG and others like it?