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diff --git a/src/corelib/tools/qsharedpointer.cpp b/src/corelib/tools/qsharedpointer.cpp
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+/****************************************************************************
+**
+** Copyright (C) 2011 Nokia Corporation and/or its subsidiary(-ies).
+** All rights reserved.
+** Contact: Nokia Corporation (qt-info@nokia.com)
+**
+** This file is part of the QtCore module of the Qt Toolkit.
+**
+** $QT_BEGIN_LICENSE:LGPL$
+** No Commercial Usage
+** This file contains pre-release code and may not be distributed.
+** You may use this file in accordance with the terms and conditions
+** contained in the Technology Preview License Agreement accompanying
+** this package.
+**
+** GNU Lesser General Public License Usage
+** Alternatively, this file may be used under the terms of the GNU Lesser
+** General Public License version 2.1 as published by the Free Software
+** Foundation and appearing in the file LICENSE.LGPL included in the
+** packaging of this file.  Please review the following information to
+** ensure the GNU Lesser General Public License version 2.1 requirements
+** will be met: http://www.gnu.org/licenses/old-licenses/lgpl-2.1.html.
+**
+** In addition, as a special exception, Nokia gives you certain additional
+** rights.  These rights are described in the Nokia Qt LGPL Exception
+** version 1.1, included in the file LGPL_EXCEPTION.txt in this package.
+**
+** If you have questions regarding the use of this file, please contact
+** Nokia at qt-info@nokia.com.
+**
+**
+**
+**
+**
+**
+**
+**
+** $QT_END_LICENSE$
+**
+****************************************************************************/
+
+#include "qsharedpointer.h"
+
+// to be sure we aren't causing a namespace clash:
+#include "qshareddata.h"
+
+/*!
+    \class QSharedPointer
+    \brief The QSharedPointer class holds a strong reference to a shared pointer
+    \since 4.5
+
+    \reentrant
+
+    The QSharedPointer is an automatic, shared pointer in C++. It
+    behaves exactly like a normal pointer for normal purposes,
+    including respect for constness.
+
+    QSharedPointer will delete the pointer it is holding when it goes
+    out of scope, provided no other QSharedPointer objects are
+    referencing it.
+
+    A QSharedPointer object can be created from a normal pointer,
+    another QSharedPointer object or by promoting a
+    QWeakPointer object to a strong reference.
+
+    \section1 Thread-Safety
+
+    QSharedPointer and QWeakPointer are thread-safe and operate
+    atomically on the pointer value. Different threads can also access
+    the QSharedPointer or QWeakPointer pointing to the same object at
+    the same time without need for locking mechanisms.
+
+    It should be noted that, while the pointer value can be accessed
+    in this manner, QSharedPointer and QWeakPointer provide no
+    guarantee about the object being pointed to. Thread-safety and
+    reentrancy rules for that object still apply.
+
+    \section1 Other Pointer Classes
+
+    Qt also provides two other pointer wrapper classes: QPointer and
+    QSharedDataPointer. They are incompatible with one another, since
+    each has its very different use case.
+
+    QSharedPointer holds a shared pointer by means of an external
+    reference count (i.e., a reference counter placed outside the
+    object). Like its name indicates, the pointer value is shared
+    among all instances of QSharedPointer and QWeakPointer. The
+    contents of the object pointed to by the pointer should not be
+    considered shared, however: there is only one object. For that
+    reason, QSharedPointer does not provide a way to detach or make
+    copies of the pointed object.
+
+    QSharedDataPointer, on the other hand, holds a pointer to shared
+    data (i.e., a class derived from QSharedData). It does so by means
+    of an internal reference count, placed in the QSharedData base
+    class. This class can, therefore, detach based on the type of
+    access made to the data being guarded: if it's a non-const access,
+    it creates a copy atomically for the operation to complete.
+
+    QExplicitlySharedDataPointer is a variant of QSharedDataPointer, except
+    that it only detaches if QExplicitlySharedDataPointer::detach() is
+    explicitly called (hence the name).
+
+    QScopedPointer simply holds a pointer to a heap allocated object and
+    deletes it in its destructor. This class is useful when an object needs to
+    be heap allocated and deleted, but no more. QScopedPointer is lightweight,
+    it makes no use of additional structure or reference counting.
+
+    Finally, QPointer holds a pointer to a QObject-derived object, but it
+    does so weakly. QPointer can be replaced by QWeakPointer in almost all
+    cases, since they have the same functionality. See
+    \l{QWeakPointer#tracking-qobject} for more information.
+
+    \section1 Optional pointer tracking
+
+    A feature of QSharedPointer that can be enabled at compile-time for
+    debugging purposes is a pointer tracking mechanism. When enabled,
+    QSharedPointer registers in a global set all the pointers that it tracks.
+    This allows one to catch mistakes like assigning the same pointer to two
+    QSharedPointer objects.
+
+    This function is enabled by defining the \tt{QT_SHAREDPOINTER_TRACK_POINTERS}
+    macro before including the QSharedPointer header.
+
+    It is safe to use this feature even with code compiled without the
+    feature. QSharedPointer will ensure that the pointer is removed from the
+    tracker even from code compiled without pointer tracking.
+
+    Note, however, that the pointer tracking feature has limitations on
+    multiple- or virtual-inheritance (that is, in cases where two different
+    pointer addresses can refer to the same object). In that case, if a
+    pointer is cast to a different type and its value changes,
+    QSharedPointer's pointer tracking mechanism may fail to detect that the
+    object being tracked is the same.
+
+    \omit
+    \secton1 QSharedPointer internals
+
+    QSharedPointer is in reality implemented by two ancestor classes:
+    QtSharedPointer::Basic and QtSharedPointer::ExternalRefCount. The reason
+    for having that split is now mostly legacy: in the beginning,
+    QSharedPointer was meant to support both internal reference counting and
+    external reference counting.
+
+    QtSharedPointer::Basic implements the basic functionality that is shared
+    between internal- and external-reference counting. That is, it's mostly
+    the accessor functions into QSharedPointer. Those are all inherited by
+    QSharedPointer, which adds another level of shared functionality (the
+    constructors and assignment operators). The Basic class has one member
+    variable, which is the actual pointer being tracked.
+
+    QtSharedPointer::ExternalRefCount implements the actual reference
+    counting and introduces the d-pointer for QSharedPointer. That d-pointer
+    itself is shared with other QSharedPointer objects as well as
+    QWeakPointer.
+
+    The reason for keeping the pointer value itself outside the d-pointer is
+    because of multiple inheritance needs. If you have two QSharedPointer
+    objects of different pointer types, but pointing to the same object in
+    memory, it could happen that the pointer values are different. The \tt
+    differentPointers autotest exemplifies this problem. The same thing could
+    happen in the case of virtual inheritance: a pointer of class matching
+    the virtual base has different address compared to the pointer of the
+    complete object. See the \tt virtualBaseDifferentPointers autotest for
+    this problem.
+
+    The d pointer is of type QtSharedPointer::ExternalRefCountData for simple
+    QSharedPointer objects, but could be of a derived type in some cases. It
+    is basically a reference-counted reference-counter.
+
+    \section2 d-pointer
+    \section3 QtSharedPointer::ExternalRefCountData
+
+    This class is basically a reference-counted reference-counter. It has two
+    members: \tt strongref and \tt weakref. The strong reference counter is
+    controlling the lifetime of the object tracked by QSharedPointer. a
+    positive value indicates that the object is alive. It's also the number
+    of QSharedObject instances that are attached to this Data.
+
+    When the strong reference count decreases to zero, the object is deleted
+    (see below for information on custom deleters). The strong reference
+    count can also exceptionally be -1, indicating that there are no
+    QSharedPointers attached to an object, which is tracked too. The only
+    case where this is possible is that of
+    \l{QWeakPointer#tracking-qobject}{QWeakPointers tracking a QObject}.
+
+    The weak reference count controls the lifetime of the d-pointer itself.
+    It can be thought of as an internal/intrusive reference count for
+    ExternalRefCountData itself. This count is equal to the number of
+    QSharedPointers and QWeakPointers that are tracking this object. (In case
+    the object tracked derives from QObject, this number is increased by 1,
+    since QObjectPrivate tracks it too).
+
+    ExternalRefCountData is a virtual class: it has a virtual destructor and
+    a virtual destroy() function. The destroy() function is supposed to
+    delete the object being tracked and return true if it does so. Otherwise,
+    it returns false to indicate that the caller must simply call delete.
+    This allows the normal use-case of QSharedPointer without custom deleters
+    to use only one 12- or 16-byte (depending on whether it's a 32- or 64-bit
+    architecture) external descriptor structure, without paying the price for
+    the custom deleter that it isn't using.
+
+    \section3 QtSharedPointer::ExternalRefCountDataWithDestroyFn
+
+    This class is not used directly, per se. It only exists to enable the two
+    classes that derive from it. It adds one member variable, which is a
+    pointer to a function (which returns void and takes an
+    ExternalRefCountData* as a parameter). It also overrides the destroy()
+    function: it calls that function pointer with \tt this as parameter, and
+    returns true.
+
+    That means when ExternalRefCountDataWithDestroyFn is used, the \tt
+    destroyer field must be set to a valid function that \b will delete the
+    object tracked.
+
+    This class also adds an operator delete function to ensure that it simply
+    calls the global operator delete. That should be the behaviour in all
+    compilers already, but to be on the safe side, this class ensures that no
+    funny business happens.
+
+    On a 32-bit architecture, this class is 16 bytes in size, whereas it's 24
+    bytes on 64-bit. (On Itanium where function pointers contain the global
+    pointer, it can be 32 bytes).
+
+    \section3 QtSharedPointer::ExternalRefCountWithCustomDeleter
+
+    This class derives from ExternalRefCountDataWithDestroyFn and is a
+    template class. As template parameters, it has the type of the pointer
+    being tracked (\tt T) and a \tt Deleter, which is anything. It adds two
+    fields to its parent class, matching those template parameters: a member
+    of type \tt Deleter and a member of type \tt T*.
+
+    The purpose of this class is to store the pointer to be deleted and the
+    deleter code along with the d-pointer. This allows the last strong
+    reference to call any arbitrary function that disposes of the object. For
+    example, this allows calling QObject::deleteLater() on a given object.
+    The pointer to the object is kept here to avoid the extra cost of keeping
+    the deleter in the generic case.
+
+    This class is never instantiated directly: the constructors and
+    destructor are private. Only the create() function may be called to
+    return an object of this type. See below for construction details.
+
+    The size of this class depends on the size of \tt Deleter. If it's an
+    empty functor (i.e., no members), ABIs generally assign it the size of 1.
+    But given that it's followed by a pointer, up to 3 or 7 padding bytes may
+    be inserted: in that case, the size of this class is 16+4+4 = 24 bytes on
+    32-bit architectures, or 24+8+8 = 40 bytes on 64-bit architectures (48
+    bytes on Itanium with global pointers stored). If \tt Deleter is a
+    function pointer, the size should be the same as the empty structure
+    case, except for Itanium where it may be 56 bytes due to another global
+    pointer. If \tt Deleter is a pointer to a member function (PMF), the size
+    will be even bigger and will depend on the ABI. For architectures using
+    the Itanium C++ ABI, a PMF is twice the size of a normal pointer, or 24
+    bytes on Itanium itself. In that case, the size of this structure will be
+    16+8+4 = 28 bytes on 32-bit architectures, 24+16+8 = 48 bytes on 64-bit,
+    and 32+24+8 = 64 bytes on Itanium.
+
+    (Values for Itanium consider an LP64 architecture; for ILP32, pointers
+    are 32-bit in length, function pointers are 64-bit and PMF are 96-bit, so
+    the sizes are slightly less)
+
+    \section3 QtSharedPointer::ExternalRefCountWithContiguousData
+
+    This class also derives from ExternalRefCountDataWithDestroyFn and it is
+    also a template class. The template parameter is the type \tt T of the
+    class which QSharedPointer tracks. It adds only one member to its parent,
+    which is of type \tt T (the actual type, not a pointer to it).
+
+    The purpose of this class is to lay the \tt T object out next to the
+    reference counts, saving one memory allocation per shared pointer. This
+    is particularly interesting for small \tt T or for the cases when there
+    are few if any QWeakPointer tracking the object. This class exists to
+    implement the QSharedPointer::create() call.
+
+    Like ExternalRefCountWithCustomDeleter, this class is never instantiated
+    directly. This class also provides a create() member that returns the
+    pointer, and hides its constructors and destructor. (With C++0x, we'd
+    delete them).
+
+    The size of this class depends on the size of \tt T.
+
+    \section3 Instantiating ExternalRefCountWithCustomDeleter and ExternalRefCountWithContiguousData
+
+    Like explained above, these classes have private constructors. Moreover,
+    they are not defined anywhere, so trying to call \tt{new ClassType} would
+    result in a compilation or linker error. Instead, these classes must be
+    constructed via their create() methods.
+
+    Instead of instantiating the class by the normal way, the create() method
+    calls \tt{operator new} directly with the size of the class, then calls
+    the parent class's constructor only (ExternalRefCountDataWithDestroyFn).
+    This ensures that the inherited members are initialised properly, as well
+    as the virtual table pointer, which must point to
+    ExternalRefCountDataWithDestroyFn's virtual table. That way, we also
+    ensure that the virtual destructor being called is
+    ExternalRefCountDataWithDestroyFn's.
+
+    After initialising the base class, the
+    ExternalRefCountWithCustomDeleter::create() function initialises the new
+    members directly, by using the placement \tt{operator new}. In the case
+    of the ExternalRefCountWithContiguousData::create() function, the address
+    to the still-uninitialised \tt T member is saved for the callee to use.
+    The member is only initialised in QSharedPointer::create(), so that we
+    avoid having many variants of the internal functions according to the
+    arguments in use for calling the constructor.
+
+    When initialising the parent class, the create() functions pass the
+    address of the static deleter() member function. That is, when the
+    virtual destroy() is called by QSharedPointer, the deleter() functions
+    are called instead. These functions static_cast the ExternalRefCountData*
+    parameter to their own type and execute their deletion: for the
+    ExternalRefCountWithCustomDeleter::deleter() case, it runs the user's
+    custom deleter, then destroys the deleter; for
+    ExternalRefCountWithContiguousData::deleter, it simply calls the \tt T
+    destructor directly.
+
+    By not calling the constructor of the derived classes, we avoid
+    instantiating their virtual tables. Since these classes are
+    template-based, there would be one virtual table per \tt T and \tt
+    Deleter type. (This is what Qt 4.5 did.)
+
+    Instead, only one non-inline function is required per template, which is
+    the deleter() static member. All the other functions can be inlined.
+    What's more, the address of deleter() is calculated only in code, which
+    can be resolved at link-time if the linker can determine that the
+    function lies in the current application or library module (since these
+    classes are not exported, that is the case for Windows or for builds with
+    \tt{-fvisibility=hidden}).
+
+    In contrast, a virtual table would require at least 3 relocations to be
+    resolved at module load-time, per module where these classes are used.
+    (In the Itanium C++ ABI, there would be more relocations, due to the
+    RTTI)
+
+    \section3 Modifications due to pointer-tracking
+
+    To ensure that pointers created with pointer-tracking enabled get
+    un-tracked when destroyed, even if destroyed by code compiled without the
+    feature, QSharedPointer modifies slightly the instructions of the
+    previous sections.
+
+    When ExternalRefCountWithCustomDeleter or
+    ExternalRefCountWithContiguousData are used, their create() functions
+    will set the ExternalRefCountDataWithDestroyFn::destroyer function
+    pointer to safetyCheckDeleter() instead. These static member functions
+    simply call internalSafetyCheckRemove2() before passing control to the
+    normal deleter() function.
+
+    If neither custom deleter nor QSharedPointer::create() are used, then
+    QSharedPointer uses a custom deleter of its own: the normalDeleter()
+    function, which simply calls \tt delete. By using a custom deleter, the
+    safetyCheckDeleter() procedure described above kicks in.
+
+    \endomit
+
+    \sa QSharedDataPointer, QWeakPointer, QScopedPointer
+*/
+
+/*!
+    \class QWeakPointer
+    \brief The QWeakPointer class holds a weak reference to a shared pointer
+    \since 4.5
+    \reentrant
+
+    The QWeakPointer is an automatic weak reference to a
+    pointer in C++. It cannot be used to dereference the pointer
+    directly, but it can be used to verify if the pointer has been
+    deleted or not in another context.
+
+    QWeakPointer objects can only be created by assignment from a
+    QSharedPointer. The exception is pointers derived from QObject: in that
+    case, QWeakPointer serves as a replacement to QPointer.
+
+    It's important to note that QWeakPointer provides no automatic casting
+    operators to prevent mistakes from happening. Even though QWeakPointer
+    tracks a pointer, it should not be considered a pointer itself, since it
+    doesn't guarantee that the pointed object remains valid.
+
+    Therefore, to access the pointer that QWeakPointer is tracking, you must
+    first promote it to QSharedPointer and verify if the resulting object is
+    null or not. QSharedPointer guarantees that the object isn't deleted, so
+    if you obtain a non-null object, you may use the pointer. See
+    QWeakPointer::toStrongRef() for an example.
+
+    QWeakPointer also provides the QWeakPointer::data() method that returns
+    the tracked pointer without ensuring that it remains valid. This function
+    is provided if you can guarantee by external means that the object will
+    not get deleted (or if you only need the pointer value) and the cost of
+    creating a QSharedPointer using toStrongRef() is too high.
+
+    That function can also be used to obtain the tracked pointer for
+    QWeakPointers that cannot be promoted to QSharedPointer, such as those
+    created directly from a QObject pointer (not via QSharedPointer).
+
+    \section1 Tracking QObject
+
+    QWeakPointer can be used to track deletion of classes that derive from QObject,
+    even if they are not managed by QSharedPointer. When used in that role,
+    QWeakPointer replaces the older QPointer in all use-cases. QWeakPointer
+    is also more efficient than QPointer, so it should be preferred in all
+    new code.
+
+    To do that, QWeakPointer provides a special constructor that is only
+    available if the template parameter \tt T is either QObject or a class
+    deriving from it. Trying to use that constructor if \tt T does not derive
+    from QObject will result in compilation errors.
+
+    To obtain the QObject being tracked by QWeakPointer, you must use the
+    QWeakPointer::data() function, but only if you can guarantee that the
+    object cannot get deleted by another context. It should be noted that
+    QPointer had the same constraint, so use of QWeakPointer forces you to
+    consider whether the pointer is still valid.
+
+    QObject-derived classes can only be deleted in the thread they have
+    affinity to (which is the thread they were created in or moved to, using
+    QObject::moveToThread()). In special, QWidget-derived classes cannot be
+    created in non-GUI threads nor moved there. Therefore, guaranteeing that
+    the tracked QObject has affinity to the current thread is enough to also
+    guarantee that it won't be deleted asynchronously.
+
+    Note that QWeakPointer's size and data layout do not match QPointer, so
+    it cannot replace that class in a binary-compatible manner.
+
+    Care must also be taken with QWeakPointers created directly from QObject
+    pointers when dealing with code that was compiled with Qt versions prior
+    to 4.6. Those versions may not track the reference counters correctly, so
+    QWeakPointers created from QObject should never be passed to code that
+    hasn't been recompiled.
+
+    \omit
+    \secton1 QWeakPointer internals
+
+    QWeakPointer shares most of its internal functionality with
+    \l{QSharedPointer#qsharedpointer-internals}{QSharedPointer}, so see that
+    class's internal documentation for more information.
+
+    QWeakPointer requires an external reference counter in order to operate.
+    Therefore, it is incompatible by design with \l QSharedData-derived
+    classes.
+
+    It has a special QObject constructor, which works by calling
+    QtSharedPointer::ExternalRefCountData::getAndRef, which retrieves the
+    d-pointer from QObjectPrivate. If one isn't set yet, that function
+    creates the d-pointer and atomically sets it.
+
+    If getAndRef needs to create a d-pointer, it sets the strongref to -1,
+    indicating that the QObject is not shared: QWeakPointer is used only to
+    determine whether the QObject has been deleted. In that case, it cannot
+    be upgraded to QSharedPointer (see the previous section).
+
+    \endomit
+
+    \sa QSharedPointer, QScopedPointer
+*/
+
+/*!
+    \fn QSharedPointer::QSharedPointer()
+
+    Creates a QSharedPointer that points to null (0).
+*/
+
+/*!
+    \fn QSharedPointer::~QSharedPointer()
+
+    Destroys this QSharedPointer object. If it is the last reference to
+    the pointer stored, this will delete the pointer as well.
+*/
+
+/*!
+    \fn QSharedPointer::QSharedPointer(T *ptr)
+
+    Creates a QSharedPointer that points to \a ptr. The pointer \a ptr
+    becomes managed by this QSharedPointer and must not be passed to
+    another QSharedPointer object or deleted outside this object.
+*/
+
+/*!
+    \fn QSharedPointer::QSharedPointer(T *ptr, Deleter deleter)
+
+    Creates a QSharedPointer that points to \a ptr. The pointer \a ptr
+    becomes managed by this QSharedPointer and must not be passed to
+    another QSharedPointer object or deleted outside this object.
+
+    The \a deleter parameter specifies the custom deleter for this
+    object. The custom deleter is called, instead of the operator delete(),
+    when the strong reference count drops to 0. This is useful,
+    for instance, for calling deleteLater() on a QObject instead:
+
+    \code
+    static void doDeleteLater(MyObject *obj)
+    {
+        obj->deleteLater();
+    }
+
+    void otherFunction()
+    {
+        QSharedPointer<MyObject> obj =
+            QSharedPointer<MyObject>(new MyObject, doDeleteLater);
+
+        // continue using obj
+        obj.clear();    // calls obj->deleteLater();
+    }
+    \endcode
+
+    It is also possible to specify a member function directly, as in:
+    \code
+        QSharedPointer<MyObject> obj =
+            QSharedPointer<MyObject>(new MyObject, &QObject::deleteLater);
+    \endcode
+
+    \sa clear()
+*/
+
+/*!
+    \fn QSharedPointer::QSharedPointer(const QSharedPointer<T> &other)
+
+    Creates a QSharedPointer object that shares \a other's pointer.
+
+    If \tt T is a derived type of the template parameter of this class,
+    QSharedPointer will perform an automatic cast. Otherwise, you will
+    get a compiler error.
+*/
+
+/*!
+    \fn QSharedPointer::QSharedPointer(const QWeakPointer<T> &other)
+
+    Creates a QSharedPointer by promoting the weak reference \a other
+    to strong reference and sharing its pointer.
+
+    If \tt T is a derived type of the template parameter of this
+    class, QSharedPointer will perform an automatic cast. Otherwise,
+    you will get a compiler error.
+
+    \sa QWeakPointer::toStrongRef()
+*/
+
+/*!
+    \fn QSharedPointer &QSharedPointer::operator=(const QSharedPointer<T> &other)
+
+    Makes this object share \a other's pointer. The current pointer
+    reference is discarded and, if it was the last, the pointer will
+    be deleted.
+
+    If \tt T is a derived type of the template parameter of this
+    class, QSharedPointer will perform an automatic cast. Otherwise,
+    you will get a compiler error.
+*/
+
+/*!
+    \fn QSharedPointer &QSharedPointer::operator=(const QWeakPointer<T> &other)
+
+    Promotes \a other to a strong reference and makes this object
+    share a reference to the pointer referenced by it. The current pointer
+    reference is discarded and, if it was the last, the pointer will
+    be deleted.
+
+    If \tt T is a derived type of the template parameter of this
+    class, QSharedPointer will perform an automatic cast. Otherwise,
+    you will get a compiler error.
+*/
+
+/*!
+    \fn T *QSharedPointer::data() const
+
+    Returns the value of the pointer referenced by this object.
+
+    Note: do not delete the pointer returned by this function or pass
+    it to another function that could delete it, including creating
+    QSharedPointer or QWeakPointer objects.
+*/
+
+/*!
+    \fn T &QSharedPointer::operator *() const
+
+    Provides access to the shared pointer's members.
+
+    \sa isNull()
+*/
+
+/*!
+    \fn T *QSharedPointer::operator ->() const
+
+    Provides access to the shared pointer's members.
+
+    \sa isNull()
+*/
+
+/*!
+    \fn bool QSharedPointer::isNull() const
+
+    Returns true if this object is holding a reference to a null
+    pointer.
+*/
+
+/*!
+    \fn QSharedPointer::operator bool() const
+
+    Returns true if this object is not null. This function is suitable
+    for use in \tt if-constructs, like:
+
+    \code
+        if (sharedptr) { ... }
+    \endcode
+
+    \sa isNull()
+*/
+
+/*!
+    \fn bool QSharedPointer::operator !() const
+
+    Returns true if this object is null. This function is suitable
+    for use in \tt if-constructs, like:
+
+    \code
+        if (!sharedptr) { ... }
+    \endcode
+
+    \sa isNull()
+*/
+
+/*!
+    \fn QSharedPointer<X> QSharedPointer::staticCast() const
+
+    Performs a static cast from this pointer's type to \tt X and returns
+    a QSharedPointer that shares the reference. This function can be
+    used for up- and for down-casting, but is more useful for
+    up-casting.
+
+    Note: the template type \c X must have the same const and volatile
+    qualifiers as the template of this object, or the cast will
+    fail. Use constCast() if you need to drop those qualifiers.
+
+    \sa dynamicCast(), constCast(), qSharedPointerCast()
+*/
+
+/*!
+    \fn QSharedPointer<X> QSharedPointer::dynamicCast() const
+
+    Performs a dynamic cast from this pointer's type to \tt X and
+    returns a QSharedPointer that shares the reference. If this
+    function is used to up-cast, then QSharedPointer will perform a \tt
+    dynamic_cast, which means that if the object being pointed by this
+    QSharedPointer is not of type \tt X, the returned object will be
+    null.
+
+    Note: the template type \c X must have the same const and volatile
+    qualifiers as the template of this object, or the cast will
+    fail. Use constCast() if you need to drop those qualifiers.
+
+    \sa qSharedPointerDynamicCast()
+*/
+
+/*!
+    \fn QSharedPointer<X> QSharedPointer::constCast() const
+
+    Performs a \tt const_cast from this pointer's type to \tt X and returns
+    a QSharedPointer that shares the reference. This function can be
+    used for up- and for down-casting, but is more useful for
+    up-casting.
+
+    \sa isNull(), qSharedPointerConstCast()
+*/
+
+/*!
+    \fn QSharedPointer<X> QSharedPointer::objectCast() const
+    \since 4.6
+
+    Performs a \l qobject_cast() from this pointer's type to \tt X and
+    returns a QSharedPointer that shares the reference. If this
+    function is used to up-cast, then QSharedPointer will perform a \tt
+    qobject_cast, which means that if the object being pointed by this
+    QSharedPointer is not of type \tt X, the returned object will be
+    null.
+
+    Note: the template type \c X must have the same const and volatile
+    qualifiers as the template of this object, or the cast will
+    fail. Use constCast() if you need to drop those qualifiers.
+
+    \sa qSharedPointerObjectCast()
+*/
+
+/*!
+    \fn QWeakPointer<T> QSharedPointer::toWeakRef() const
+
+    Returns a weak reference object that shares the pointer referenced
+    by this object.
+
+    \sa QWeakPointer::QWeakPointer()
+*/
+
+/*!
+    \fn void QSharedPointer::clear()
+
+    Clears this QSharedPointer object, dropping the reference that it
+    may have had to the pointer. If this was the last reference, then
+    the pointer itself will be deleted.
+*/
+
+/*!
+    \fn QWeakPointer::QWeakPointer()
+
+    Creates a QWeakPointer that points to nothing.
+*/
+
+/*!
+    \fn QWeakPointer::~QWeakPointer()
+
+    Destroys this QWeakPointer object. The pointer referenced
+    by this object will not be deleted.
+*/
+
+/*!
+    \fn QWeakPointer::QWeakPointer(const QWeakPointer<T> &other)
+
+    Creates a QWeakPointer that holds a weak reference to the
+    pointer referenced by \a other.
+
+    If \tt T is a derived type of the template parameter of this
+    class, QWeakPointer will perform an automatic cast. Otherwise,
+    you will get a compiler error.
+*/
+
+/*!
+    \fn QWeakPointer::QWeakPointer(const QSharedPointer<T> &other)
+
+    Creates a QWeakPointer that holds a weak reference to the
+    pointer referenced by \a other.
+
+    If \tt T is a derived type of the template parameter of this
+    class, QWeakPointer will perform an automatic cast. Otherwise,
+    you will get a compiler error.
+*/
+
+/*!
+    \fn QWeakPointer::QWeakPointer(const QObject *obj)
+    \since 4.6
+
+    Creates a QWeakPointer that holds a weak reference directly to the
+    QObject \a obj. This constructor is only available if the template type
+    \tt T is QObject or derives from it (otherwise a compilation error will
+    result).
+
+    You can use this constructor with any QObject, even if they were not
+    created with \l QSharedPointer.
+
+    Note that QWeakPointers created this way on arbitrary QObjects usually
+    cannot be promoted to QSharedPointer.
+
+    \sa QSharedPointer, QWeakPointer#tracking-qobject
+*/
+
+/*!
+    \fn QWeakPointer &QWeakPointer::operator=(const QObject *obj)
+    \since 4.6
+
+    Makes this QWeakPointer hold a weak reference directly to the QObject
+    \a obj. This function is only available if the template type \tt T is
+    QObject or derives from it.
+
+    \sa QWeakPointer#tracking-qobject
+*/
+
+/*!
+    \fn QWeakPointer &QWeakPointer::operator=(const QWeakPointer<T> &other)
+
+    Makes this object share \a other's pointer. The current pointer
+    reference is discarded but is not deleted.
+
+    If \tt T is a derived type of the template parameter of this
+    class, QWeakPointer will perform an automatic cast. Otherwise,
+    you will get a compiler error.
+*/
+
+/*!
+    \fn QWeakPointer &QWeakPointer::operator=(const QSharedPointer<T> &other)
+
+    Makes this object share \a other's pointer. The current pointer
+    reference is discarded but is not deleted.
+
+    If \tt T is a derived type of the template parameter of this
+    class, QWeakPointer will perform an automatic cast. Otherwise,
+    you will get a compiler error.
+*/
+
+/*!
+    \fn bool QWeakPointer::isNull() const
+
+    Returns true if this object is holding a reference to a null
+    pointer.
+
+    Note that, due to the nature of weak references, the pointer that
+    QWeakPointer references can become null at any moment, so
+    the value returned from this function can change from false to
+    true from one call to the next.
+*/
+
+/*!
+    \fn QWeakPointer::operator bool() const
+
+    Returns true if this object is not null. This function is suitable
+    for use in \tt if-constructs, like:
+
+    \code
+        if (weakref) { ... }
+    \endcode
+
+    Note that, due to the nature of weak references, the pointer that
+    QWeakPointer references can become null at any moment, so
+    the value returned from this function can change from true to
+    false from one call to the next.
+
+    \sa isNull()
+*/
+
+/*!
+    \fn bool QWeakPointer::operator !() const
+
+    Returns true if this object is null. This function is suitable
+    for use in \tt if-constructs, like:
+
+    \code
+        if (!weakref) { ... }
+    \endcode
+
+    Note that, due to the nature of weak references, the pointer that
+    QWeakPointer references can become null at any moment, so
+    the value returned from this function can change from false to
+    true from one call to the next.
+
+    \sa isNull()
+*/
+
+/*!
+    \fn T *QWeakPointer::data() const
+    \since 4.6
+
+    Returns the value of the pointer being tracked by this QWeakPointer,
+    \b without ensuring that it cannot get deleted. To have that guarantee,
+    use toStrongRef(), which returns a QSharedPointer object. If this
+    function can determine that the pointer has already been deleted, it
+    returns 0.
+
+    It is ok to obtain the value of the pointer and using that value itself,
+    like for example in debugging statements:
+
+    \code
+        qDebug("Tracking %p", weakref.data());
+    \endcode
+
+    However, dereferencing the pointer is only allowed if you can guarantee
+    by external means that the pointer does not get deleted. For example,
+    if you can be certain that no other thread can delete it, nor the
+    functions that you may call.
+
+    If that is the case, then the following code is valid:
+
+    \code
+        // this pointer cannot be used in another thread
+        // so other threads cannot delete it
+        QWeakPointer<int> weakref = obtainReference();
+
+        Object *obj = weakref.data();
+        if (obj) {
+            // if the pointer wasn't deleted yet, we know it can't get
+            // deleted by our own code here nor the functions we call
+            otherFunction(obj);
+        }
+    \endcode
+
+    Use this function with care.
+
+    \sa isNull(), toStrongRef()
+*/
+
+/*!
+    \fn QSharedPointer<T> QWeakPointer::toStrongRef() const
+
+    Promotes this weak reference to a strong one and returns a
+    QSharedPointer object holding that reference. When promoting to
+    QSharedPointer, this function verifies if the object has been deleted
+    already or not. If it hasn't, this function increases the reference
+    count to the shared object, thus ensuring that it will not get
+    deleted.
+
+    Since this function can fail to obtain a valid strong reference to the
+    shared object, you should always verify if the conversion succeeded,
+    by calling QSharedPointer::isNull() on the returned object.
+
+    For example, the following code promotes a QWeakPointer that was held
+    to a strong reference and, if it succeeded, it prints the value of the
+    integer that was held:
+
+    \code
+        QWeakPointer<int> weakref;
+
+        // ...
+
+        QSharedPointer<int> strong = weakref.toStrongRef();
+        if (strong)
+            qDebug() << "The value is:" << *strong;
+        else
+            qDebug() << "The value has already been deleted";
+    \endcode
+
+    \sa QSharedPointer::QSharedPointer()
+*/
+
+/*!
+    \fn void QWeakPointer::clear()
+
+    Clears this QWeakPointer object, dropping the reference that it
+    may have had to the pointer.
+*/
+
+/*!
+    \fn bool operator==(const QSharedPointer<T> &ptr1, const QSharedPointer<X> &ptr2)
+    \relates QSharedPointer
+
+    Returns true if the pointer referenced by \a ptr1 is the
+    same pointer as that referenced by \a ptr2.
+
+    If \a ptr2's template parameter is different from \a ptr1's,
+    QSharedPointer will attempt to perform an automatic \tt static_cast
+    to ensure that the pointers being compared are equal. If \a ptr2's
+    template parameter is not a base or a derived type from
+    \a ptr1's, you will get a compiler error.
+*/
+
+/*!
+    \fn bool operator!=(const QSharedPointer<T> &ptr1, const QSharedPointer<X> &ptr2)
+    \relates QSharedPointer
+
+    Returns true if the pointer referenced by \a ptr1 is not the
+    same pointer as that referenced by \a ptr2.
+
+    If \a ptr2's template parameter is different from \a ptr1's,
+    QSharedPointer will attempt to perform an automatic \tt static_cast
+    to ensure that the pointers being compared are equal. If \a ptr2's
+    template parameter is not a base or a derived type from
+    \a ptr1's, you will get a compiler error.
+*/
+
+/*!
+    \fn bool operator==(const QSharedPointer<T> &ptr1, const X *ptr2)
+    \relates QSharedPointer
+
+    Returns true if the pointer referenced by \a ptr1 is the
+    same pointer as \a ptr2.
+
+    If \a ptr2's type is different from \a ptr1's,
+    QSharedPointer will attempt to perform an automatic \tt static_cast
+    to ensure that the pointers being compared are equal. If \a ptr2's
+    type is not a base or a derived type from this
+    \a ptr1's, you will get a compiler error.
+*/
+
+/*!
+    \fn bool operator!=(const QSharedPointer<T> &ptr1, const X *ptr2)
+    \relates QSharedPointer
+
+    Returns true if the pointer referenced by \a ptr1 is not the
+    same pointer as \a ptr2.
+
+    If \a ptr2's type is different from \a ptr1's,
+    QSharedPointer will attempt to perform an automatic \tt static_cast
+    to ensure that the pointers being compared are equal. If \a ptr2's
+    type is not a base or a derived type from this
+    \a ptr1's, you will get a compiler error.
+*/
+
+/*!
+    \fn bool operator==(const T *ptr1, const QSharedPointer<X> &ptr2)
+    \relates QSharedPointer
+
+    Returns true if the pointer \a ptr1 is the
+    same pointer as that referenced by \a ptr2.
+
+    If \a ptr2's template parameter is different from \a ptr1's type,
+    QSharedPointer will attempt to perform an automatic \tt static_cast
+    to ensure that the pointers being compared are equal. If \a ptr2's
+    template parameter is not a base or a derived type from
+    \a ptr1's type, you will get a compiler error.
+*/
+
+/*!
+    \fn bool operator!=(const T *ptr1, const QSharedPointer<X> &ptr2)
+    \relates QSharedPointer
+
+    Returns true if the pointer \a ptr1 is not the
+    same pointer as that referenced by \a ptr2.
+
+    If \a ptr2's template parameter is different from \a ptr1's type,
+    QSharedPointer will attempt to perform an automatic \tt static_cast
+    to ensure that the pointers being compared are equal. If \a ptr2's
+    template parameter is not a base or a derived type from
+    \a ptr1's type, you will get a compiler error.
+*/
+
+/*!
+    \fn bool operator==(const QSharedPointer<T> &ptr1, const QWeakPointer<X> &ptr2)
+    \relates QWeakPointer
+
+    Returns true if the pointer referenced by \a ptr1 is the
+    same pointer as that referenced by \a ptr2.
+
+    If \a ptr2's template parameter is different from \a ptr1's,
+    QSharedPointer will attempt to perform an automatic \tt static_cast
+    to ensure that the pointers being compared are equal. If \a ptr2's
+    template parameter is not a base or a derived type from
+    \a ptr1's, you will get a compiler error.
+*/
+
+/*!
+    \fn bool operator!=(const QSharedPointer<T> &ptr1, const QWeakPointer<X> &ptr2)
+    \relates QWeakPointer
+
+    Returns true if the pointer referenced by \a ptr1 is not the
+    same pointer as that referenced by \a ptr2.
+
+    If \a ptr2's template parameter is different from \a ptr1's,
+    QSharedPointer will attempt to perform an automatic \tt static_cast
+    to ensure that the pointers being compared are equal. If \a ptr2's
+    template parameter is not a base or a derived type from
+    \a ptr1's, you will get a compiler error.
+*/
+
+/*!
+    \fn bool operator==(const QWeakPointer<T> &ptr1, const QSharedPointer<X> &ptr2)
+    \relates QWeakPointer
+
+    Returns true if the pointer referenced by \a ptr1 is the
+    same pointer as that referenced by \a ptr2.
+
+    If \a ptr2's template parameter is different from \a ptr1's,
+    QSharedPointer will attempt to perform an automatic \tt static_cast
+    to ensure that the pointers being compared are equal. If \a ptr2's
+    template parameter is not a base or a derived type from
+    \a ptr1's, you will get a compiler error.
+*/
+
+/*!
+    \fn bool operator!=(const QWeakPointer<T> &ptr1, const QSharedPointer<X> &ptr2)
+    \relates QWeakPointer
+
+    Returns true if the pointer referenced by \a ptr1 is not the
+    same pointer as that referenced by \a ptr2.
+
+    If \a ptr2's template parameter is different from \a ptr1's,
+    QSharedPointer will attempt to perform an automatic \tt static_cast
+    to ensure that the pointers being compared are equal. If \a ptr2's
+    template parameter is not a base or a derived type from
+    \a ptr1's, you will get a compiler error.
+*/
+
+/*!
+    \fn QSharedPointer<X> qSharedPointerCast(const QSharedPointer<T> &other)
+    \relates QSharedPointer
+
+    Returns a shared pointer to the pointer held by \a other, cast to
+    type \tt X.  The types \tt T and \tt X must belong to one
+    hierarchy for the \tt static_cast to succeed.
+
+    Note that \tt X must have the same cv-qualifiers (\tt const and
+    \tt volatile) that \tt T has, or the code will fail to
+    compile. Use qSharedPointerConstCast to cast away the constness.
+
+    \sa QSharedPointer::staticCast(), qSharedPointerDynamicCast(), qSharedPointerConstCast()
+*/
+
+/*!
+    \fn QSharedPointer<X> qSharedPointerCast(const QWeakPointer<T> &other)
+    \relates QSharedPointer
+    \relates QWeakPointer
+
+    Returns a shared pointer to the pointer held by \a other, cast to
+    type \tt X.  The types \tt T and \tt X must belong to one
+    hierarchy for the \tt static_cast to succeed.
+
+    The \a other object is converted first to a strong reference. If
+    that conversion fails (because the object it's pointing to has
+    already been deleted), this function returns a null
+    QSharedPointer.
+
+    Note that \tt X must have the same cv-qualifiers (\tt const and
+    \tt volatile) that \tt T has, or the code will fail to
+    compile. Use qSharedPointerConstCast to cast away the constness.
+
+    \sa QWeakPointer::toStrongRef(), qSharedPointerDynamicCast(), qSharedPointerConstCast()
+*/
+
+/*!
+    \fn QSharedPointer<X> qSharedPointerDynamicCast(const QSharedPointer<T> &other)
+    \relates QSharedPointer
+
+    Returns a shared pointer to the pointer held by \a other, using a
+    dynamic cast to type \tt X to obtain an internal pointer of the
+    appropriate type. If the \tt dynamic_cast fails, the object
+    returned will be null.
+
+    Note that \tt X must have the same cv-qualifiers (\tt const and
+    \tt volatile) that \tt T has, or the code will fail to
+    compile. Use qSharedPointerConstCast to cast away the constness.
+
+    \sa QSharedPointer::dynamicCast(), qSharedPointerCast(), qSharedPointerConstCast()
+*/
+
+/*!
+    \fn QSharedPointer<X> qSharedPointerDynamicCast(const QWeakPointer<T> &other)
+    \relates QSharedPointer
+    \relates QWeakPointer
+
+    Returns a shared pointer to the pointer held by \a other, using a
+    dynamic cast to type \tt X to obtain an internal pointer of the
+    appropriate type. If the \tt dynamic_cast fails, the object
+    returned will be null.
+
+    The \a other object is converted first to a strong reference. If
+    that conversion fails (because the object it's pointing to has
+    already been deleted), this function also returns a null
+    QSharedPointer.
+
+    Note that \tt X must have the same cv-qualifiers (\tt const and
+    \tt volatile) that \tt T has, or the code will fail to
+    compile. Use qSharedPointerConstCast to cast away the constness.
+
+    \sa QWeakPointer::toStrongRef(), qSharedPointerCast(), qSharedPointerConstCast()
+*/
+
+/*!
+    \fn QSharedPointer<X> qSharedPointerConstCast(const QSharedPointer<T> &other)
+    \relates QSharedPointer
+
+    Returns a shared pointer to the pointer held by \a other, cast to
+    type \tt X.  The types \tt T and \tt X must belong to one
+    hierarchy for the \tt const_cast to succeed. The \tt const and \tt
+    volatile differences between \tt T and \tt X are ignored.
+
+    \sa QSharedPointer::constCast(), qSharedPointerCast(), qSharedPointerDynamicCast()
+*/
+
+/*!
+    \fn QSharedPointer<X> qSharedPointerConstCast(const QWeakPointer<T> &other)
+    \relates QSharedPointer
+    \relates QWeakPointer
+
+    Returns a shared pointer to the pointer held by \a other, cast to
+    type \tt X. The types \tt T and \tt X must belong to one
+    hierarchy for the \tt const_cast to succeed. The \tt const and
+    \tt volatile differences between \tt T and \tt X are ignored.
+
+    The \a other object is converted first to a strong reference. If
+    that conversion fails (because the object it's pointing to has
+    already been deleted), this function returns a null
+    QSharedPointer.
+
+    \sa QWeakPointer::toStrongRef(), qSharedPointerCast(), qSharedPointerDynamicCast()
+*/
+
+/*!
+    \fn QSharedPointer<X> qSharedPointerObjectCast(const QSharedPointer<T> &other)
+    \relates QSharedPointer
+    \since 4.6
+
+    \brief The qSharedPointerObjectCast function is for casting a shared pointer.
+
+    Returns a shared pointer to the pointer held by \a other, using a
+    \l qobject_cast() to type \tt X to obtain an internal pointer of the
+    appropriate type. If the \tt qobject_cast fails, the object
+    returned will be null.
+
+    Note that \tt X must have the same cv-qualifiers (\tt const and
+    \tt volatile) that \tt T has, or the code will fail to
+    compile. Use qSharedPointerConstCast to cast away the constness.
+
+    \sa QSharedPointer::objectCast(), qSharedPointerCast(), qSharedPointerConstCast()
+*/
+
+/*!
+    \fn QSharedPointer<X> qSharedPointerObjectCast(const QWeakPointer<T> &other)
+    \relates QSharedPointer
+    \relates QWeakPointer
+    \since 4.6
+
+    \brief The qSharedPointerObjectCast function is for casting a shared pointer.
+
+    Returns a shared pointer to the pointer held by \a other, using a
+    \l qobject_cast() to type \tt X to obtain an internal pointer of the
+    appropriate type. If the \tt qobject_cast fails, the object
+    returned will be null.
+
+    The \a other object is converted first to a strong reference. If
+    that conversion fails (because the object it's pointing to has
+    already been deleted), this function also returns a null
+    QSharedPointer.
+
+    Note that \tt X must have the same cv-qualifiers (\tt const and
+    \tt volatile) that \tt T has, or the code will fail to
+    compile. Use qSharedPointerConstCast to cast away the constness.
+
+    \sa QWeakPointer::toStrongRef(), qSharedPointerCast(), qSharedPointerConstCast()
+*/
+
+
+/*!
+    \fn QWeakPointer<X> qWeakPointerCast(const QWeakPointer<T> &other)
+    \relates QWeakPointer
+
+    Returns a weak pointer to the pointer held by \a other, cast to
+    type \tt X. The types \tt T and \tt X must belong to one
+    hierarchy for the \tt static_cast to succeed.
+
+    Note that \tt X must have the same cv-qualifiers (\tt const and
+    \tt volatile) that \tt T has, or the code will fail to
+    compile. Use qSharedPointerConstCast to cast away the constness.
+*/
+
+#include <qset.h>
+#include <qmutex.h>
+
+#if !defined(QT_NO_QOBJECT)
+#include "private/qobject_p.h"
+
+QT_BEGIN_NAMESPACE
+
+/*!
+    \internal
+    This function is called for a just-created QObject \a obj, to enable
+    the use of QSharedPointer and QWeakPointer.
+
+    When QSharedPointer is active in a QObject, the object must not be deleted
+    directly: the lifetime is managed by the QSharedPointer object. In that case,
+    the deleteLater() and parent-child relationship in QObject only decrease
+    the strong reference count, instead of deleting the object.
+*/
+void QtSharedPointer::ExternalRefCountData::setQObjectShared(const QObject *obj, bool)
+{
+    Q_ASSERT(obj);
+    QObjectPrivate *d = QObjectPrivate::get(const_cast<QObject *>(obj));
+
+    if (d->sharedRefcount)
+        qFatal("QSharedPointer: pointer %p already has reference counting", obj);
+    d->sharedRefcount = this;
+
+    // QObject decreases the refcount too, so increase it up
+    weakref.ref();
+}
+
+QtSharedPointer::ExternalRefCountData *QtSharedPointer::ExternalRefCountData::getAndRef(const QObject *obj)
+{
+    Q_ASSERT(obj);
+    QObjectPrivate *d = QObjectPrivate::get(const_cast<QObject *>(obj));
+    Q_ASSERT_X(!d->wasDeleted, "QWeakPointer", "Detected QWeakPointer creation in a QObject being deleted");
+
+    ExternalRefCountData *that = d->sharedRefcount;
+    if (that) {
+        that->weakref.ref();
+        return that;
+    }
+
+    // we can create the refcount data because it doesn't exist
+    ExternalRefCountData *x = new ExternalRefCountData(Qt::Uninitialized);
+    x->strongref = -1;
+    x->weakref = 2;  // the QWeakPointer that called us plus the QObject itself
+    if (!d->sharedRefcount.testAndSetRelease(0, x)) {
+        delete x;
+        d->sharedRefcount->weakref.ref();
+    }
+    return d->sharedRefcount;
+}
+
+QT_END_NAMESPACE
+
+#endif
+
+
+
+//#  define QT_SHARED_POINTER_BACKTRACE_SUPPORT
+#  ifdef QT_SHARED_POINTER_BACKTRACE_SUPPORT
+#    if defined(__GLIBC__) && (__GLIBC__ >= 2) && !defined(__UCLIBC__) && !defined(QT_LINUXBASE)
+#      define BACKTRACE_SUPPORTED
+#    elif defined(Q_OS_MACX)
+#      define BACKTRACE_SUPPORTED
+#    endif
+#  endif
+
+#  if defined(BACKTRACE_SUPPORTED)
+#    include <sys/types.h>
+#    include <execinfo.h>
+#    include <stdio.h>
+#    include <unistd.h>
+#    include <sys/wait.h>
+
+QT_BEGIN_NAMESPACE
+
+static inline QByteArray saveBacktrace() __attribute__((always_inline));
+static inline QByteArray saveBacktrace()
+{
+    static const int maxFrames = 32;
+
+    QByteArray stacktrace;
+    stacktrace.resize(sizeof(void*) * maxFrames);
+    int stack_size = backtrace((void**)stacktrace.data(), maxFrames);
+    stacktrace.resize(sizeof(void*) * stack_size);
+
+    return stacktrace;
+}
+
+static void printBacktrace(QByteArray stacktrace)
+{
+    void *const *stack = (void *const *)stacktrace.constData();
+    int stack_size = stacktrace.size() / sizeof(void*);
+    char **stack_symbols = backtrace_symbols(stack, stack_size);
+
+    int filter[2];
+    pid_t child = -1;
+    if (pipe(filter) != -1)
+        child = fork();
+    if (child == 0) {
+        // child process
+        dup2(fileno(stderr), fileno(stdout));
+        dup2(filter[0], fileno(stdin));
+        close(filter[0]);
+        close(filter[1]);
+        execlp("c++filt", "c++filt", "-n", NULL);
+
+        // execlp failed
+        execl("/bin/cat", "/bin/cat", NULL);
+        _exit(127);
+    }
+
+    // parent process
+    close(filter[0]);
+    FILE *output;
+    if (child == -1) {
+        // failed forking
+        close(filter[1]);
+        output = stderr;
+    } else {
+        output = fdopen(filter[1], "w");
+    }
+
+    fprintf(stderr, "Backtrace of the first creation (most recent frame first):\n");
+    for (int i = 0; i < stack_size; ++i) {
+        if (strlen(stack_symbols[i]))
+            fprintf(output, "#%-2d %s\n", i, stack_symbols[i]);
+        else
+            fprintf(output, "#%-2d %p\n", i, stack[i]);
+    }
+
+    if (child != -1) {
+        fclose(output);
+        waitpid(child, 0, 0);
+    }
+}
+
+QT_END_NAMESPACE
+
+#  endif  // BACKTRACE_SUPPORTED
+
+namespace {
+    QT_USE_NAMESPACE
+    struct Data {
+        const volatile void *pointer;
+#  ifdef BACKTRACE_SUPPORTED
+        QByteArray backtrace;
+#  endif
+    };
+
+    class KnownPointers
+    {
+    public:
+        QMutex mutex;
+        QHash<const void *, Data> dPointers;
+        QHash<const volatile void *, const void *> dataPointers;
+    };
+}
+
+Q_GLOBAL_STATIC(KnownPointers, knownPointers)
+
+QT_BEGIN_NAMESPACE
+
+namespace QtSharedPointer {
+    Q_CORE_EXPORT void internalSafetyCheckAdd(const volatile void *);
+    Q_CORE_EXPORT void internalSafetyCheckRemove(const volatile void *);
+    Q_AUTOTEST_EXPORT void internalSafetyCheckCleanCheck();
+}
+
+/*!
+    \internal
+*/
+void QtSharedPointer::internalSafetyCheckAdd(const volatile void *)
+{
+    // Qt 4.5 compatibility
+    // this function is broken by design, so it was replaced with internalSafetyCheckAdd2
+    //
+    // it's broken because we tracked the pointers added and
+    // removed from QSharedPointer, converted to void*.
+    // That is, this is supposed to track the "top-of-object" pointer in
+    // case of multiple inheritance.
+    //
+    // However, it doesn't work well in some compilers:
+    // if you create an object with a class of type A and the last reference
+    // is dropped of type B, then the value passed to internalSafetyCheckRemove could
+    // be different than was added. That would leave dangling addresses.
+    //
+    // So instead, we track the pointer by the d-pointer instead.
+}
+
+/*!
+    \internal
+*/
+void QtSharedPointer::internalSafetyCheckRemove(const volatile void *)
+{
+    // Qt 4.5 compatibility
+    // see comments above
+}
+
+/*!
+    \internal
+*/
+void QtSharedPointer::internalSafetyCheckAdd2(const void *d_ptr, const volatile void *ptr)
+{
+    // see comments above for the rationale for this function
+    KnownPointers *const kp = knownPointers();
+    if (!kp)
+        return;                 // end-game: the application is being destroyed already
+
+    QMutexLocker lock(&kp->mutex);
+    Q_ASSERT(!kp->dPointers.contains(d_ptr));
+
+    //qDebug("Adding d=%p value=%p", d_ptr, ptr);
+
+    const void *other_d_ptr = kp->dataPointers.value(ptr, 0);
+    if (other_d_ptr) {
+#  ifdef BACKTRACE_SUPPORTED
+        printBacktrace(knownPointers()->dPointers.value(other_d_ptr).backtrace);
+#  endif
+        qFatal("QSharedPointer: internal self-check failed: pointer %p was already tracked "
+               "by another QSharedPointer object %p", ptr, other_d_ptr);
+    }
+
+    Data data;
+    data.pointer = ptr;
+#  ifdef BACKTRACE_SUPPORTED
+    data.backtrace = saveBacktrace();
+#  endif
+
+    kp->dPointers.insert(d_ptr, data);
+    kp->dataPointers.insert(ptr, d_ptr);
+    Q_ASSERT(kp->dPointers.size() == kp->dataPointers.size());
+}
+
+/*!
+    \internal
+*/
+void QtSharedPointer::internalSafetyCheckRemove2(const void *d_ptr)
+{
+    KnownPointers *const kp = knownPointers();
+    if (!kp)
+        return;                 // end-game: the application is being destroyed already
+
+    QMutexLocker lock(&kp->mutex);
+
+    QHash<const void *, Data>::iterator it = kp->dPointers.find(d_ptr);
+    if (it == kp->dPointers.end()) {
+        qFatal("QSharedPointer: internal self-check inconsistency: pointer %p was not tracked. "
+               "To use QT_SHAREDPOINTER_TRACK_POINTERS, you have to enable it throughout "
+               "in your code.", d_ptr);
+    }
+
+    QHash<const volatile void *, const void *>::iterator it2 = kp->dataPointers.find(it->pointer);
+    Q_ASSERT(it2 != kp->dataPointers.end());
+
+    //qDebug("Removing d=%p value=%p", d_ptr, it->pointer);
+
+    // remove entries
+    kp->dataPointers.erase(it2);
+    kp->dPointers.erase(it);
+    Q_ASSERT(kp->dPointers.size() == kp->dataPointers.size());
+}
+
+/*!
+    \internal
+    Called by the QSharedPointer autotest
+*/
+void QtSharedPointer::internalSafetyCheckCleanCheck()
+{
+#  ifdef QT_BUILD_INTERNAL
+    KnownPointers *const kp = knownPointers();
+    Q_ASSERT_X(kp, "internalSafetyCheckSelfCheck()", "Called after global statics deletion!");
+
+    if (kp->dPointers.size() != kp->dataPointers.size())
+        qFatal("Internal consistency error: the number of pointers is not equal!");
+
+    if (!kp->dPointers.isEmpty())
+        qFatal("Pointer cleaning failed: %d entries remaining", kp->dPointers.size());
+#  endif
+}
+
+QT_END_NAMESPACE