gdb, debug with separate debug file and different source dir problem

a4z · 10-16-2014, 04:37 AM

Hi,

I have to use a special version for qt,
this comes with libQtWhatever.so.VERSION and libQtWhatever.so.VERSION.debug
I downloaded the Qt VERSION sources

now I need to debug and step through some Qt methods
but it does not work

I have used
set debug-file-directory /where/the/lib/are
(lib and lib.debug are in the same dir)

and
directory /where/I/expect/the/source

(in fact, for directory I used several versions, like ..src/widgets and src/widgets/graphicsview)

but it does not work, I can not step into the qt code and inspect the location where I have the crash

what am I doing wrong?

firstfire · 10-16-2014, 06:19 AM

Hi.

Just guessing: are you sure that the executable file you are debugging actually uses your compiled library? Maybe you need to set LD_PRELOAD environment variable?

a4z · 10-16-2014, 07:07 AM

using ldd I can see it points exactly to those libraries
there is also no alternative (since there are no other qt5 libs on this system)
so I assume that I am either doing something wrong, or files miss something

I am also not sure if I have a problem with the debug libs,
I get good info where the crash happens, backtrace an method call that causes the problem
but I can not step (nor does is stop at the location where the crash happens)

if this

Quote:

readelf -a libQt5Widgets.so.5.1.1 | grep debug
[25] .gnu_debuglink PROGBITS 00000000 5c857c 000024 00 0 0 1

a valid debuglink ?

norobro · 10-16-2014, 11:03 AM

Just guessing here, too:

Quote:

lib and lib.debug are in the same dir

Are there symlinks in the directory also? e.g.:

Quote:

@libQtWhatever.so

If so, try changing them to point to the respective debug libraries

firstfire · 10-16-2014, 11:32 AM

Hi.

Try

Code:

(gdb) sharedlibrary libQtWhatever
(gdb) info sources

to check that debug symbols are loaded and to find out where gdb expect to find source files for your library. What exactly happens when you try to step into some qt5 function?

a4z · 10-17-2014, 01:55 AM

sharedlibrary ....
Symbols already loaded for ....(full path)

info sources,
a long list, and the qt sources are loaded, so everything is here

it seems that my lookup path is messed up or I need to to a path substitution, need to find out what

when I step into qt function, nothing happens, (list shows nothing), tui is showing me my code where the call is done.

parts of sources look like this

Quote:

../../include/QtGui/5.1.1/QtGui/private/../../../../../src/gui/text/qtextdocumentlayout_p.h, .moc/debug-shared/moc_qgraphicsitem.cpp,
../../include/QtGui/5.1.1/QtGui/private/../../../../../src/gui/text/qtextengine_p.h, graphicsview/qgraphicsitem.cpp, ../../include/QtGui/../../src/gui/text/qtextobject.h,
../../include/QtGui/../../src/gui/text/qtextlayout.h, ../../include/QtGui/../../src/gui/text/qtextformat.h, ../../include/QtGui/../../src/gui/math3d/qmatrix4x4.h,
graphicsview/qgraphicsgridlayout.cpp, graphicsview/qgraphicsgridlayout.h, ../../include/QtWidgets/../../src/widgets/widgets/qplaintextedit.h,
../../include/QtWidgets/../../src/widgets/widgets/qtextedit.h, ../../include/QtWidgets/../../src/widgets/itemviews/qtableview.h,
../../include/QtWidgets/5.1.1/QtWidgets/private/../../../../../src/widgets/itemviews/qitemeditorfactory_p.h, ../../include/QtWidgets/../../src/widgets/widgets/qlineedit

or

Quote:

/home/somePerson/some/where/qt/qt-5.1.1/qt-everywhere-opensource-src-5.1.1/qtbase/include/QtCore/../../src/corelib/xml/qxmlstream.h,

so it seems I have to fiddle and play around with setting the right source dirs and path substitution