[Webkit-unassigned] [Bug 25932] New: Unitialized variable used at JSC::Heap::markConservatively and JSC::CollectorBitmap::set

[bugzilla-daemon at webkit.org]

https://bugs.webkit.org/show_bug.cgi?id=25932

           Summary: Unitialized variable used at
                    JSC::Heap::markConservatively and
                    JSC::CollectorBitmap::set
           Product: WebKit
           Version: 528+ (Nightly build)
          Platform: PC
        OS/Version: Linux
            Status: UNCONFIRMED
          Severity: Normal
          Priority: P2
         Component: JavaScriptCore
        AssignedTo: webkit-unassigned at lists.webkit.org
        ReportedBy: webkit at dpinol.com


valgrind detected an Unitialized variable used at
JSC::Heap::markConservatively.

1)
Thanks to --track-origins=yes below you can see that the source unitialized
value comes from JSC::Heap::markCurrentThreadConservativelyInternal()
(Collector.cpp:700)

==8572== Conditional jump or move depends on uninitialised value(s)
==8572==    at 0x42776D7: JSC::Heap::markConservatively(void*, void*)
(Collector.cpp:669)
==8572==    by 0x427780C: JSC::Heap::markCurrentThreadConservativelyInternal()
(Collector.cpp:704)
==8572==    by 0x427783D: JSC::Heap::markCurrentThreadConservatively()
(Collector.cpp:720)
==8572==    by 0x4277858: JSC::Heap::markStackObjectsConservatively()
(Collector.cpp:872)
==8572==    by 0x4277C14: JSC::Heap::collect() (Collector.cpp:1084)
==8572==    by 0x4317A76:
WebCore::GCController::gcTimerFired(WebCore::Timer<WebCore::GCController>*)
(GCController.cpp:74)
==8572==    by 0x4317C39: WebCore::Timer<WebCore::GCController>::fired()
(Timer.h:99)
==8572==    by 0x46FF8AB: WebCore::TimerBase::fireTimers(double,
WTF::Vector<WebCore::TimerBase*, 0u> const&) (Timer.cpp:347)
==8572==    by 0x46FF944: WebCore::TimerBase::sharedTimerFired()
(Timer.cpp:368)
==8572==    by 0x485BA6D: WebCore::SharedTimerQt::timerEvent(QTimerEvent*)
(SharedTimerQt.cpp:105)
==8572==    by 0x63AB203: QObject::event(QEvent*) (qobject.cpp:1073)
==8572==    by 0x546488A: QApplicationPrivate::notify_helper(QObject*, QEvent*)
(qapplication.cpp:4057)
==8572==    by 0x5462CEB: QApplication::notify(QObject*, QEvent*)
(qapplication.cpp:3604)
==8572==    by 0x63957AC: QCoreApplication::notifyInternal(QObject*, QEvent*)
(qcoreapplication.cpp:610)
==8572==    by 0x48564E8: QCoreApplication::sendEvent(QObject*, QEvent*)
(qcoreapplication.h:213)
==8572==  Uninitialised value was created by a stack allocation
==8572==    at 0x42777E3: JSC::Heap::markCurrentThreadConservativelyInternal()
(Collector.cpp:700)


2) In this case value comes from QApplication::notify
==8572== Use of uninitialised value of size 4
==8572==    at 0x41A9C2F: JSC::CollectorBitmap::set(unsigned int)
(Collector.h:191)
==8572==    by 0x41A9CA5: JSC::Heap::markCell(JSC::JSCell*) (Collector.h:276)
==8572==    by 0x427773F: JSC::Heap::markConservatively(void*, void*)
(Collector.cpp:677)
==8572==    by 0x427780C: JSC::Heap::markCurrentThreadConservativelyInternal()
(Collector.cpp:704)
==8572==    by 0x427783D: JSC::Heap::markCurrentThreadConservatively()
(Collector.cpp:720)
==8572==    by 0x4277858: JSC::Heap::markStackObjectsConservatively()
(Collector.cpp:872)
==8572==    by 0x4277C14: JSC::Heap::collect() (Collector.cpp:1084)
==8572==    by 0x4317A76:
WebCore::GCController::gcTimerFired(WebCore::Timer<WebCore::GCController>*)
(GCController.cpp:74)
==8572==    by 0x4317C39: WebCore::Timer<WebCore::GCController>::fired()
(Timer.h:99)
==8572==    by 0x46FF8AB: WebCore::TimerBase::fireTimers(double,
WTF::Vector<WebCore::TimerBase*, 0u> const&) (Timer.cpp:347)
==8572==    by 0x46FF944: WebCore::TimerBase::sharedTimerFired()
(Timer.cpp:368)
==8572==    by 0x485BA6D: WebCore::SharedTimerQt::timerEvent(QTimerEvent*)
(SharedTimerQt.cpp:105)
==8572==    by 0x63AB203: QObject::event(QEvent*) (qobject.cpp:1073)
==8572==    by 0x546488A: QApplicationPrivate::notify_helper(QObject*, QEvent*)
(qapplication.cpp:4057)
==8572==    by 0x5462CEB: QApplication::notify(QObject*, QEvent*)
(qapplication.cpp:3604)
==8572==  Uninitialised value was created by a stack allocation
==8572==    at 0x54629BA: QApplication::notify(QObject*, QEvent*)
(qapplication.cpp:3532)


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