/**************************************************************************** ** ** Copyright (C) 2009 Nokia Corporation and/or its subsidiary(-ies). ** Contact: Qt Software Information (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 either Technology Preview License Agreement or the ** Beta Release License Agreement. ** ** 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 1.0, included in the file LGPL_EXCEPTION.txt in this ** package. ** ** GNU General Public License Usage ** Alternatively, this file may be used under the terms of the GNU ** General Public License version 3.0 as published by the Free Software ** Foundation and appearing in the file LICENSE.GPL included in the ** packaging of this file. Please review the following information to ** ensure the GNU General Public License version 3.0 requirements will be ** met: http://www.gnu.org/copyleft/gpl.html. ** ** If you are unsure which license is appropriate for your use, please ** contact the sales department at qt-sales@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 \ingroup misc 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 same QSharedPointer or QWeakPointer 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 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 behaves like QSharedDataPointer, except that it only detaches if QExplicitlySharedDataPointer::detach() is explicitly called. Finally, QPointer holds a pointer to a QObject-derived object, but it does so weakly. QPointer is similar, in that behaviour, to QWeakPointer: it does not allow you to prevent the object from being destroyed. All you can do is query whether it has been destroyed or not. \sa QSharedDataPointer, QWeakPointer */ /*! \class QWeakPointer \brief The QWeakPointer class holds a weak reference to a shared pointer \since 4.5 \reentrant \ingroup misc 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. To access the pointer that QWeakPointer is tracking, you must first create a QSharedPointer object and verify if the pointer is null or not. \sa QSharedPointer */ /*! \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 paramter specifies the custom deleter for this object. The custom deleter is called when the strong reference count drops to 0 instead of the operator delete(). This is useful, for instance, for calling deleteLater() in a QObject instead: \code static void doDeleteLater(MyObject *obj) { obj->deleteLater(); } void otherFunction() { QSharedPointer obj = QSharedPointer(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 obj = QSharedPointer(new MyObject, &QObject::deleteLater); \endcode \sa clear() */ /*! \fn QSharedPointer::QSharedPointer(const QSharedPointer &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 &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. */ /*! \fn QSharedPointer &QSharedPointer::operator=(const QSharedPointer &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 &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 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 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 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 QWeakPointer QSharedPointer::toWeakRef() const Returns a weak reference object that shares the pointer referenced by this object. */ /*! \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 &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 &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::operator=(const QWeakPointer &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 &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 QSharedPointer QWeakPointer::toStrongRef() const Promotes this weak reference to a strong one and returns a QSharedPointer object holding that reference. */ /*! \fn void QWeakPointer::clear() Clears this QWeakPointer object, dropping the reference that it may have had to the pointer. */ /*! \fn bool operator==(const QSharedPointer &ptr1, const QSharedPointer &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 &ptr1, const QSharedPointer &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 &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 &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 &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 &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 &ptr1, const QWeakPointer &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 &ptr1, const QWeakPointer &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 &ptr1, const QSharedPointer &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 &ptr1, const QSharedPointer &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 qSharedPointerCast(const QSharedPointer &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 qSharedPointerCast(const QWeakPointer &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 qSharedPointerDynamicCast(const QSharedPointer &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 qSharedPointerDynamicCast(const QWeakPointer &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 qSharedPointerConstCast(const QSharedPointer &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 qSharedPointerConstCast(const QWeakPointer &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 QWeakPointer qWeakPointerCast(const QWeakPointer &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 #include #if !defined(QT_NO_MEMBER_TEMPLATES) //# 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) // Dummy implementation of the functions. // Using QHashDummyValue also means that the QHash below is actually a QSet typedef QT_PREPEND_NAMESPACE(QHashDummyValue) Backtrace; static inline Backtrace saveBacktrace() { return Backtrace(); } static inline void printBacktrace(Backtrace) { } # else # include # include # include # include # include typedef QT_PREPEND_NAMESPACE(QByteArray) Backtrace; static inline Backtrace saveBacktrace() __attribute__((always_inline)); static inline Backtrace saveBacktrace() { static const int maxFrames = 32; Backtrace 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(Backtrace 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); } } # endif // BACKTRACE_SUPPORTED namespace { QT_USE_NAMESPACE class KnownPointers { public: QMutex mutex; QHash values; }; } Q_GLOBAL_STATIC(KnownPointers, knownPointers) QT_BEGIN_NAMESPACE /*! \internal */ void QtSharedPointer::internalSafetyCheckAdd(const volatile void *ptr) { QMutexLocker lock(&knownPointers()->mutex); void *actual = const_cast(ptr); if (knownPointers()->values.contains(actual)) { printBacktrace(knownPointers()->values.value(actual)); qFatal("QSharedPointerData: internal self-check failed: pointer %p was already tracked " "by another QSharedPointerData object", actual); } knownPointers()->values.insert(actual, saveBacktrace()); } /*! \internal */ void QtSharedPointer::internalSafetyCheckRemove(const volatile void *ptr) { QMutexLocker lock(&knownPointers()->mutex); void *actual = const_cast(ptr); knownPointers()->values.remove(actual); } QT_END_NAMESPACE #endif