QSharedPointer: make QT_SHAREDPOINTER_TRACK_POINTERS work with QObjects

If setQObjectShared crashes because a QObject is tracked by two
different QSharedPointers, we lose the debug feature offered by #defining
QT_SHAREDPOINTER_TRACK_POINTERS, as the check done by this define
happens after the setQObjectShared call.

Therefore, move setQObjectShared after the internalSafetyCheckAdd2 call.

This way, the error raised by QSharedPointer created changes from f.i.

  QSharedPointer: pointer 0xa10010 already has reference counting

to the more "debuggable" (and consistent with non-QObjects)

  QSharedPointer: internal self-check failed: pointer 0x1dd90e0 was already tracked by another QSharedPointer object 0x1dd9330

"Backport" of change-id I71340d0f878828354537762d01c46d441efc918c from
qtbase (although, as of commit 609b0a9c2e69180ceff5d89c42e0d9468491d7e3,
this issue is not present there, as setQObjectShared does nothing).

Change-Id: I4cea83d705795eae0e05da128a3f189aea36f5ce
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>

2 files changed, 8 insertions, 1 deletions

diff --git a/src/corelib/tools/qsharedpointer_impl.h b/src/corelib/tools/qsharedpointer_impl.h
index 4216456..95864a1 100644
--- a/src/corelib/tools/qsharedpointer_impl.h
+++ b/src/corelib/tools/qsharedpointer_impl.h
@@ -378,10 +378,10 @@ namespace QtSharedPointer {
         inline void internalFinishConstruction(T *ptr)
         {
             Basic<T>::internalConstruct(ptr);
-            if (ptr) d->setQObjectShared(ptr, true);
 #ifdef QT_SHAREDPOINTER_TRACK_POINTERS
             if (ptr) internalSafetyCheckAdd2(d, ptr);
 #endif
+            if (ptr) d->setQObjectShared(ptr, true);
         }
 
         inline ExternalRefCount() : d(0) { }
diff --git a/tests/auto/qsharedpointer/tst_qsharedpointer.cpp b/tests/auto/qsharedpointer/tst_qsharedpointer.cpp
index 452e658..54fe65e 100644
--- a/tests/auto/qsharedpointer/tst_qsharedpointer.cpp
+++ b/tests/auto/qsharedpointer/tst_qsharedpointer.cpp
@@ -1755,6 +1755,13 @@ void tst_QSharedPointer::invalidConstructs_data()
            "QSharedPointer<Data> ptr1 = QSharedPointer<Data>(aData);\n"
            "QSharedPointer<Data> ptr2 = QSharedPointer<Data>(aData);\n";
 
+    // two QObjects with the same pointer
+    QTest::newRow("same-pointer-to-qobject")
+        << &QTest::QExternalTest::tryRunFail
+        << "QObject *anObj = new QObject;\n"
+           "QSharedPointer<QObject> ptr1 = QSharedPointer<QObject>(anObj);\n"
+           "QSharedPointer<QObject> ptr2 = QSharedPointer<QObject>(anObj);\n";
+
     // re-creation:
     QTest::newRow("re-creation")
         << &QTest::QExternalTest::tryRunFail