[Qt-interest] Please confirm critical bug

[Clinton Stimpson]

You need
Application(int&, char**) instead to match QApplication's constructor.

Clint

Dmitry Baryshev wrote:
> Hi. I've found strange behaviour of QApplication subclass and
> setProperty(). I've subclasses QApplication and put this subclass into
> separate TU (and this is important). Then in main.cpp I created
> Application instance and call setProperty() on it. After app.exec()
> application crashed. In general, application does nothing but calls
> setProperty() on Application's object. And this causes segfault. The
> second very weird problem is that if you put Application subclass
> directly into main.cpp, it will work fine.
>
> And plus one problem more - If I call QCoreApplication::argc() exactly
> after setProperty(), it will return some uninitialized value
> (134517064 for example), and it will return "1" as expected if i don't
> call setProperty(). If I call QCoreApplication::arguments() exactly
> after setProperty(), it will crash immediately.
>
> This crash doesn't depend on existance of Q_OBJECT in QApplication subclass.
>
> This is very strange and seems to be a memory corruption somewhere in
> QApplication or QObject::setProperty(). Small source code is attached
> and also goes here.
>
> application.h:
> ----------------
> #ifndef G_APPLICATION_H
> #define G_APPLICATION_H
>
> #ifdef REPRODUCE
>
> #include <QApplication>
>
> class Application : public QApplication
> {
>     public:
>         Application(int, char **);
> };
>
> #endif
>
> #endif
>
> application.cpp:
> -------------------
> #ifdef REPRODUCE
> #include "application.h"
>
> Application::Application(int argc, char **argv) : QApplication(argc, argv)
> {}
> #endif
>
> main.cpp:
> -----------
> #include <QApplication>
> #include <QVariant>
> #include <QDebug>
>
> #include "application.h"
>
> #ifndef REPRODUCE
> // this will not crash for some reason
> class Application : public QApplication
> {
>     public:
>         Application(int argc, char **argv) : QApplication(argc, argv)
>         {}
> };
> #endif
>
> int main(int argc, char *argv[])
> {
>     Application app(argc, argv);
>
>     app.setProperty("hello", "hello");
>
>     // will crash
>     //QStringList list = app.arguments();
>
>     // segfault
>     return app.exec();
> }
>
> .pro:
> -----
>
> TEMPLATE = app
> TARGET =
> DEPENDPATH += .
> INCLUDEPATH += .
>
> CONFIG += warn_on release
>
> # Input
> HEADERS += application.h
> SOURCES += main.cpp application.cpp
>
> QMAKE_CXXFLAGS += -DREPRODUCE
>
> -------------------
>
> ltrace output:
>
> $ ltrace -C ./qt4-template
> __libc_start_main(0x8048e60, 1, 0xbffb6d24, 0x8048ff0, 0x8048fe0
> <unfinished ...>
> QApplication::QApplication(int&, char**, int)(0xbffb6c70, 0xbffb6c44,
> 0xbffb6d24, 263171, 0xb7466268 <unfinished ...>
> QObject::childEvent(QChildEvent*)(0xbffb6c70, 0xbffb6a58, 0xbffb6940,
> 0, 0)                     = 0xb767ffa8
> QApplication::notify(QObject*, QEvent*)(0xbffb6c70, 0xbffb6c70,
> 0xbffb5dd8, 0, 0x91ff260 <unfinished ...>
> QApplication::event(QEvent*)(0xbffb6c70, 0xbffb5dd8, 0xbffb5dd8,
> 0xbffb6c70, 0xbffb5d28 <unfinished ...>
> QObject::childEvent(QChildEvent*)(0xbffb6c70, 0xbffb5dd8, 0xb7fb97c4,
> 0, 0)                     = 0xb7f644a8
> <... QApplication::event(QEvent*) resumed> )
>                          = 1
> <... QApplication::notify(QObject*, QEvent*) resumed> )
>                          = 1
> QApplication::notify(QObject*, QEvent*)(0xbffb6c70, 0xbffb6c70,
> 0xbffb6978, 0, 0x91ff260 <unfinished ...>
> QApplication::event(QEvent*)(0xbffb6c70, 0xbffb6978, 0xbffb6978,
> 0xb7db7bc3, 0xb7db7bd6 <unfinished ...>
> QObject::childEvent(QChildEvent*)(0xbffb6c70, 0xbffb6978, 2, 4081,
> 0xbffb6ab4)                  = 0xb7f644a8
> <... QApplication::event(QEvent*) resumed> )
>                          = 1
> <... QApplication::notify(QObject*, QEvent*) resumed> )
>                          = 1
> QApplication::notify(QObject*, QEvent*)(0xbffb6c70, 0x92298e0,
> 0xbffb6948, 0xb7680778, 0x91ff260 <unfinished ...>
> QObject::childEvent(QChildEvent*)(0x92298e0, 0xbffb6948, 0xbffb6638,
> 0xb71770cd, 0xbffb6920)    = 0xb7f654a8
> <... QApplication::notify(QObject*, QEvent*) resumed> )
>                          = 1
> QObject::connectNotify(char const*)(0x922e640, 0xb7db8320, 0x92298e0,
> 4, 0)                     = 0x922e640
> <... QApplication::QApplication(int&, char**, int) resumed> )
>                          = 263171
> QVariant::QVariant(char const*)(0xbffb6c64, 0x80490a8, 0xbffb6d24,
> 0xb71efd30, 0xb7f79734)      = 0x9234ed0
> QObject::setProperty(char const*, QVariant const&)(0xbffb6c70,
> 0x80490a8, 0xbffb6c64, 0xb71efd30, 0xb7f79734 <unfinished ...>
> QApplication::metaObject() const(0xbffb6c70, 0xb746ca48, 0xb7f9caf0,
> 0xb7680778, -1)            = 0xb7f64488
> QApplication::notify(QObject*, QEvent*)(0xbffb6c70, 0xbffb6c70,
> 0xbffb6c0c, 0xb7483b4b, 0x91ff260 <unfinished ...>
> QApplication::event(QEvent*)(0xbffb6c70, 0xbffb6c0c, 0xbffb6c0c, 0, 1)
>                          = 0
> <... QApplication::notify(QObject*, QEvent*) resumed> )
>                          = 0
> <... QObject::setProperty(char const*, QVariant const&) resumed> )
>                          = 0
> QVariant::~QVariant()(0xbffb6c64, 0x80490a8, 0xbffb6c64, 0xb71efd30,
> 0xb7f79734)                = 0x9234ed0
> QApplication::exec()(0xbffb6c64, 0x80490a8, 0xbffb6c64, 0xb71efd30,
> 0xb7f79734 <unfinished ...>
> QApplication::notify(QObject*, QEvent*)(0xbffb6c70, 0xbffb6c70,
> 0x9206400, 0xb6e20090, 0x91ff260 <unfinished ...>
> QApplication::event(QEvent*)(0xbffb6c70, 0x9206400, 0x9206400, 0,
> 0x9bdaf51 <unfinished ...>
> QApplication::notify(QObject*, QEvent*)(0xbffb6c70, 0xbffb6c70,
> 0xbffb654c, 0x556b9394, 0x91ff260 <unfinished ...>
> QApplication::event(QEvent*)(0xbffb6c70, 0xbffb654c, 0xbffb654c,
> 0xb7fa73bd, 6 <unfinished ...>
> QObject::childEvent(QChildEvent*)(0xbffb6c70, 0xbffb654c, 0xb7fb8ff4,
> 0x10822fdb, 0xb71aa6f0)   = 0x80490c8
> <... QApplication::event(QEvent*) resumed> )
>                          = 1
> <... QApplication::notify(QObject*, QEvent*) resumed> )
>                          = 1
> QApplication::notify(QObject*, QEvent*)(0xbffb6c70, 0xbffb6c70,
> 0xbffb654c, 0x556b9394, 0x91ff260 <unfinished ...>
> QApplication::event(QEvent*)(0xbffb6c70, 0xbffb654c, 0xbffb654c,
> 0xb7fa73bd, 6 <unfinished ...>
> QObject::childEvent(QChildEvent*)(0xbffb6c70, 0xbffb654c, 0xb7fb8ff4,
> 0x10822fdb, 0xb71aa6f0)   = 0x80490c8
> <... QApplication::event(QEvent*) resumed> )
>                          = 1
> <... QApplication::notify(QObject*, QEvent*) resumed> )
>                          = 1
> QApplication::notify(QObject*, QEvent*)(0xbffb6c70, 0xbffb6c70,
> 0xbffb654c, 0x556b9394, 0x91ff260 <unfinished ...>
> QApplication::event(QEvent*)(0xbffb6c70, 0xbffb654c, 0xbffb654c,
> 0xb7fa73bd, 6 <unfinished ...>
> QObject::childEvent(QChildEvent*)(0xbffb6c70, 0xbffb654c, 0xb7fb8ff4,
> 0x10822fdb, 0xb71aa6f0)   = 0x80490c8
> <... QApplication::event(QEvent*) resumed> )
>                          = 1
> <... QApplication::notify(QObject*, QEvent*) resumed> )
>                          = 1
> <... QApplication::event(QEvent*) resumed> )
>                          = 1
> <... QApplication::notify(QObject*, QEvent*) resumed> )
>                          = 1
> QApplication::notify(QObject*, QEvent*)(0xbffb6c70, 0x92298e0,
> 0x924eaf0, 0xb7435ff4, 0x91ff260 <unfinished ...>
> QApplication::notify(QObject*, QEvent*)(0xbffb6c70, 0x92298e0,
> 0xbffb65dc, 0xb71770cd, 0x91ff260 <unfinished ...>
> QObject::childEvent(QChildEvent*)(0x92298e0, 0xbffb65dc, 0xb6e12b28,
> 0xb7f79734, 0xbffb654c)    = 0xb7f654a8
> <... QApplication::notify(QObject*, QEvent*) resumed> )
>                          = 1
> <... QApplication::notify(QObject*, QEvent*) resumed> )
>                          = 1
> QApplication::notify(QObject*, QEvent*)(0xbffb6c70, 0x922e640,
> 0xbffb6a10, 0x92298e0, 0x91ff260 <unfinished ...>
> --- SIGSEGV (Segmentation fault) ---
> +++ killed by SIGSEGV +++
>
> -------------------
>
> The system is Debian Lenny with gcc 4.3.2, Qt 4.4.3, Qt 4.5 is also
> affected (tested with LD_LIBRARY_PATH). Can anybody reproduce this in
> Linux? Thanks!
>
> --
>   
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>
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