summaryrefslogtreecommitdiffstats
path: root/src/corelib/tools/qsharedpointer.cpp
blob: 4fecc9ac6bdcc13f9153751bda6db9de5326418a (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
830
831
832
833
834
835
836
837
838
839
840
841
842
843
844
845
846
847
848
849
850
851
852
853
854
855
856
857
858
859
860
861
862
863
864
865
866
867
868
869
870
871
872
873
874
875
876
877
878
879
880
881
882
883
884
885
886
887
888
889
890
891
892
893
894
895
896
897
898
899
900
901
902
903
904
905
906
907
908
909
910
911
912
913
914
915
916
917
918
919
920
921
922
923
924
925
926
927
928
929
930
931
932
933
934
935
936
937
938
939
940
941
942
943
944
945
946
947
948
949
950
951
952
953
954
955
956
957
958
959
960
961
962
963
964
965
966
967
968
969
970
971
972
973
974
975
976
977
978
979
980
981
982
983
984
985
986
987
988
989
990
991
992
993
994
995
996
997
998
999
1000
1001
1002
1003
1004
1005
1006
1007
1008
1009
1010
1011
1012
1013
1014
1015
1016
1017
1018
1019
1020
1021
1022
1023
1024
1025
1026
1027
1028
1029
1030
1031
1032
1033
1034
1035
1036
1037
1038
1039
1040
1041
1042
1043
1044
1045
1046
1047
1048
1049
1050
1051
1052
1053
1054
1055
1056
1057
1058
1059
1060
1061
1062
1063
1064
1065
1066
1067
1068
1069
1070
1071
1072
1073
1074
1075
1076
1077
1078
1079
1080
1081
1082
1083
1084
1085
1086
1087
1088
1089
1090
1091
1092
1093
1094
1095
1096
1097
1098
1099
1100
1101
1102
1103
1104
1105
1106
1107
1108
1109
1110
1111
1112
1113
1114
1115
1116
1117
1118
1119
1120
1121
1122
1123
1124
1125
1126
1127
1128
1129
1130
1131
1132
1133
1134
1135
1136
1137
1138
1139
1140
1141
1142
1143
1144
/****************************************************************************
**
** Copyright (C) 2009 Nokia Corporation and/or its subsidiary(-ies).
** 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 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 http://www.qtsoftware.com/contact.
** $QT_END_LICENSE$
**
****************************************************************************/

#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.

    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 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, QScopedPointer
*/

/*!
    \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. See QWeakPointer::toStrongRef() for more information.

    \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 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<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::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

    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

    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 "../kernel/qobject_p.h"

/*!
    \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));
    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;
}
#endif



#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)
#    include <sys/types.h>
#    include <execinfo.h>
#    include <stdio.h>
#    include <unistd.h>
#    include <sys/wait.h>

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);
    }
}
#  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

#endif