[SOLVED] Linux, Qt 5.2.1: C++/QML application crash only in debug mode

nbertin

Hi,

I'm looking for advice / tips on how to debug this strange issue.
My host/target system is Linux (Ubuntu 12.04LTS 64bits) and Qt5.2.1

1- the application (C++ & QML) compiled in release mode is running without any issue
2- the same application compiled in debug mode is crashing in the QApplication exec() method
3- the same application compiled in debug mode but started with valgrind is not crashing

The backtrace is always the same, but doesn't give much information (at least to me)...
__strlen_sse2
QCoreApplication::arguments()
??
??
_SmcProcessMessage
IceProcessMessage
...

Thank you for help!

andreyc

Could you post full backtrace from a core file and your source code related to the backtrace.

nbertin

Unfortunately, I can't disclose the source code and it's a quite big project! It's running already on Win32 and OSX and we are porting it to Linux (desktop first and then, to a Freescale i.MX6 hardware).

Anyway, I've finally found and fixed the issue!

Early in the code, a factory instantiates a QApplication or QtSingleApplication with argc and argv as parameters.
In debug mode, the "-qmljsdebugger=port:...,block" argument is added (but not in release mode, which explain why it doesn't crash). This argument is removed (by QApplication?) and argc/argv are updated accordingly.

Because argc was not passed by reference to the factory, its value was wrong on return (+1 compared to the number of entries in argv) = crashes when Qt tries to get the length of a non-existant argument !

andreyc

Glad to hear that the is resolved. Thank you for sharing your investigation results.