https://bugs.kde.org/show_bug.cgi?id=439897
Bug ID: 439897
Summary: Heaptrack produces impossible/incorrect stack traces
Product: Heaptrack
Version: unspecified
Platform: Gentoo Packages
OS: Linux
Status: REPORTED
Severity: normal
Priority: NOR
Component: general
Assignee: m...@milianw.de
Reporter: k...@mattwhitlock.name
Target Milestone: ---
SUMMARY
I'm trying to use Heaptrack to find a memory leak in plasmashell, but Heaptrack
is producing some nonsensical stack traces that purport to contain impossible
calls.
STEPS TO REPRODUCE
1. heaptrack plasmashell
2. (use plasmashell for a bit to exercise a suspected leak)
3. kquitapp5 plasmashell
4. heaptrack --analyze heaptrack.plasmashell.*.zst
or heaptrack_print heaptrack.plasmashell.*.zst
OBSERVED RESULT
Analysis contains "impossible" stack traces like (for example):
94095 calls with 0B peak consumption from:
QString::reallocData(unsigned int, bool)
at
../../../qtbase-everywhere-src-5.15.2/src/corelib/text/qstring.cpp:2372
in /usr/lib64/libQt5Core.so.5
QString::resize(int)
at
../../../qtbase-everywhere-src-5.15.2/src/corelib/text/qstring.cpp:2289
in /usr/lib64/libQt5Core.so.5
std::__atomic_base<>::load(std::memory_order) const
at
/usr/lib/gcc/x86_64-pc-linux-gnu/11.1.0/include/g++-v11/bits/atomic_base.h:481
in /usr/lib64/libQt5Core.so.5
int QAtomicOps<>::loadRelaxed<>(std::atomic<> const&)
at
../../../qtbase-everywhere-src-5.15.2/include/QtCore/../../src/corelib/thread/qatomic_cxx11.h:239
QBasicAtomicInteger<>::loadRelaxed() const
at
../../../qtbase-everywhere-src-5.15.2/include/QtCore/../../src/corelib/thread/qbasicatomic.h:107
QtPrivate::RefCount::isShared() const
at
../../../qtbase-everywhere-src-5.15.2/include/QtCore/../../src/corelib/tools/qrefcount.h:101
QString::detach()
at
../../../qtbase-everywhere-src-5.15.2/include/QtCore/../../src/corelib/text/qstring.h:1088
QString::data()
at
../../../qtbase-everywhere-src-5.15.2/include/QtCore/../../src/corelib/text/qstring.h:1084
operator>>(QDataStream&, QString&)
at
../../../qtbase-everywhere-src-5.15.2/src/corelib/text/qstring.cpp:10418
QDataStream& QtPrivate::readArrayBasedContainer<>(QDataStream&, QVector<>&)
at /usr/include/qt5/QtCore/qdatastream.h:257
in /usr/lib64/libKF5Service.so.5
KServicePrivate::load(QDataStream&)
at ../kservice-5.84.0/src/services/kservice.cpp:324
in /usr/lib64/libKF5Service.so.5
KService::KService(QDataStream&, int)
at ../kservice-5.84.0/src/services/kservice.cpp:384
in /usr/lib64/libKF5Service.so.5
KServiceFactory::createEntry(int) const
at ../kservice-5.84.0/src/services/kservicefactory.cpp:207
in /usr/lib64/libKF5Service.so.5
KServiceFactory::serviceOffers(int, int)
at ../kservice-5.84.0/src/services/kservicefactory.cpp:301
in /usr/lib64/libKF5Service.so.5
KServiceTypeTrader::defaultOffers(QString const&, QString const&) const
at ../kservice-5.84.0/src/services/kservicetypetrader.cpp:114
in /usr/lib64/libKF5Service.so.5
KServiceTypeTrader::query(QString const&, QString const&) const
at ../kservice-5.84.0/src/services/kservicetypetrader.cpp:144
in /usr/lib64/libKF5Service.so.5
QString::~QString()
at /usr/include/qt5/QtCore/qstring.h:1307
in /usr/lib64/libnotificationmanager.so.1
NotificationManager::Notification::Private::serviceForDesktopEntry(QString
const&)
at /usr/include/qt5/QtCore/qstring.h:1307
QExplicitlySharedDataPointer<>::operator bool() const
at /usr/include/qt5/QtCore/qshareddata.h:176
in /usr/lib64/libnotificationmanager.so.1
NotificationManager::Notification::Private::setDesktopEntry(QString const&)
at ../plasma-workspace-5.22.3/libnotificationmanager/notification.cpp:303
QString::~QString()
at /usr/include/qt5/QtCore/qstring.h:1307
in /usr/lib64/libnotificationmanager.so.1
NotificationManager::Notification::Private::processHints(QMap<> const&)
at ../plasma-workspace-5.22.3/libnotificationmanager/notification.cpp:345
NotificationManager::ServerPrivate::Notify(QString const&, unsigned int,
QString const&, QString const&, QString const&, QStringList const&, QMap<>
const&, int)
at ../plasma-workspace-5.22.3/libnotificationmanager/server_p.cpp:184
in /usr/lib64/libnotificationmanager.so.1
NotificationsAdaptor::Notify(QString const&, unsigned int, QString const&,
QString const&, QString const&, QStringList const&, QMap<> const&, int)
at libnotificationmanager/notificationsadaptor.cpp:70
in /usr/lib64/libnotificationmanager.so.1
NotificationsAdaptor::qt_static_metacall(QObject*, QMetaObject::Call, int,
void**)
at libnotificationmanager/notificationsadaptor.moc:185
in /usr/lib64/libnotificationmanager.so.1
NotificationsAdaptor::qt_metacall(QMetaObject::Call, int, void**)
at libnotificationmanager/notificationsadaptor.moc:258
in /usr/lib64/libnotificationmanager.so.1
QDBusConnectionPrivate::deliverCall(QObject*, int, QDBusMessage const&,
QVector<> const&, int)
at
../../../qtbase-everywhere-src-5.15.2/src/dbus/qdbusintegrator.cpp:1001
in /usr/lib64/libQt5DBus.so.5
QDBusConnectionPrivate::activateCall(QObject*, int, QDBusMessage const&)
at ../../../qtbase-everywhere-src-5.15.2/src/dbus/qdbusintegrator.cpp:912
in /usr/lib64/libQt5DBus.so.5
QDBusConnectionPrivate::activateObject(QDBusConnectionPrivate::ObjectTreeNode&,
QDBusMessage const&, int)
at
../../../qtbase-everywhere-src-5.15.2/src/dbus/qdbusintegrator.cpp:1497
in /usr/lib64/libQt5DBus.so.5
QDBusConnectionPrivate::activateObject(QDBusConnectionPrivate::ObjectTreeNode&,
QDBusMessage const&, int)
at
../../../qtbase-everywhere-src-5.15.2/src/dbus/qdbusintegrator.cpp:1461
in /usr/lib64/libQt5DBus.so.5
QDBusActivateObjectEvent::placeMetaCall(QObject*)
at
../../../qtbase-everywhere-src-5.15.2/src/dbus/qdbusintegrator.cpp:1617
QObjectPrivate::Sender::~Sender()
at
../../../qtbase-everywhere-src-5.15.2/src/corelib/kernel/qobject_p.h:212
in /usr/lib64/libQt5Core.so.5
QObject::event(QEvent*)
at
../../../qtbase-everywhere-src-5.15.2/src/corelib/kernel/qobject.cpp:1316
QCoreApplicationPrivate::setEventSpontaneous(QEvent*, bool)
at /usr/include/qt5/QtCore/5.15.2/QtCore/private/qcoreapplication_p.h:119
in /usr/lib64/libQt5Widgets.so.5
QApplicationPrivate::notify_helper(QObject*, QEvent*)
at
../../../qtbase-everywhere-src-5.15.2/src/widgets/kernel/qapplication.cpp:3634
QCoreApplication::notifyInternal2(QObject*, QEvent*)
at
../../../qtbase-everywhere-src-5.15.2/src/corelib/kernel/qcoreapplication.cpp:1063
in /usr/lib64/libQt5Core.so.5
QScopedPointerDeleter<>::cleanup(QEvent*)
at
../../../qtbase-everywhere-src-5.15.2/include/QtCore/../../src/corelib/tools/qscopedpointer.h:60
in /usr/lib64/libQt5Core.so.5
QScopedPointer<>::~QScopedPointer()
at
../../../qtbase-everywhere-src-5.15.2/include/QtCore/../../src/corelib/tools/qscopedpointer.h:107
QCoreApplicationPrivate::sendPostedEvents(QObject*, int, QThreadData*)
at
../../../qtbase-everywhere-src-5.15.2/src/corelib/kernel/qcoreapplication.cpp:1822
postEventSourceDispatch
at
../../../qtbase-everywhere-src-5.15.2/src/corelib/kernel/qeventdispatcher_glib.cpp:278
in /usr/lib64/libQt5Core.so.5
g_main_dispatch
at ../glib-2.68.3/glib/gmain.c:3347
in /usr/lib64/libglib-2.0.so.0
g_main_context_dispatch
at ../glib-2.68.3/glib/gmain.c:4055
g_main_context_iterate
at ../glib-2.68.3/glib/gmain.c:4131
in /usr/lib64/libglib-2.0.so.0
g_main_context_iteration
at ../glib-2.68.3/glib/gmain.c:4197
in /usr/lib64/libglib-2.0.so.0
QEventDispatcherGlib::processEvents(QFlags<>)
at
../../../qtbase-everywhere-src-5.15.2/src/corelib/kernel/qeventdispatcher_glib.cpp:424
in /usr/lib64/libQt5Core.so.5
std::__atomic_base<>::load(std::memory_order) const
at
/usr/lib/gcc/x86_64-pc-linux-gnu/11.1.0/include/g++-v11/bits/atomic_base.h:481
in /usr/lib64/libQt5Core.so.5
int QAtomicOps<>::loadAcquire<>(std::atomic<> const&)
at
../../../qtbase-everywhere-src-5.15.2/include/QtCore/../../src/corelib/thread/qatomic_cxx11.h:251
QBasicAtomicInteger<>::loadAcquire() const
at
../../../qtbase-everywhere-src-5.15.2/include/QtCore/../../src/corelib/thread/qbasicatomic.h:110
QEventLoop::exec(QFlags<>)
at
../../../qtbase-everywhere-src-5.15.2/src/corelib/kernel/qeventloop.cpp:231
QCoreApplication::exec()
at
../../../qtbase-everywhere-src-5.15.2/src/corelib/kernel/qcoreapplication.cpp:1371
in /usr/lib64/libQt5Core.so.5
main
at ../plasma-workspace-5.22.3/shell/main.cpp:254
in /usr/bin/plasmashell
Notice that QString::~QString() allegedly calls
NotificationManager::Notification::Private::setDesktopEntry(QString const&),
which leads to another call to QString::~QString(), which allegedly calls
KServiceTypeTrader::query(QString const&, QString const&) const.
If we look at the actual implementation of QString::~QString(), we find:
inline QString::~QString() { if (!d->ref.deref()) Data::deallocate(d); }
The deref() call is just an atomic decrement of an integer, and
Data::deallocate(d) just calls ::free(d) after making some assertions. There is
no way that QString::~QString() is calling into those other functions.
You might think that there's some weird interaction between the compiler's
optimizer and the debug info since QString::~QString() is an inlined function,
but /usr/lib64/libnotificationmanager.so.1 was compiled with '-Og -ggdb', which
is supposed to produce sensible debug info.
Another example: std::__atomic_base<>::load(std::memory_order) const supposedly
makes calls to both QEventDispatcherGlib::processEvents(QFlags<>) and
QString::resize(int). That's preposterous.
EXPECTED RESULT
Stack traces should not purport to contain function calls that do not appear in
the source code.
SOFTWARE/OS VERSIONS
Heaptrack Version: 1.2.80 (66a7ba44c)
Linux/KDE Plasma: Gentoo Linux
KDE Plasma Version: 5.22.3
KDE Frameworks Version: 5.84.0
Qt Version: 5.15.2
GCC Version: Gentoo 11.1.0-r1 p2
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