2 files changed, 29 insertions, 21 deletions

diff --git a/src/corelib/tools/qhash.h b/src/corelib/tools/qhash.h
index 5e3016d313..b15dc7b07b 100644
--- a/src/corelib/tools/qhash.h
+++ b/src/corelib/tools/qhash.h
@@ -554,11 +554,15 @@ QHash<Key, T>::createNode(uint ah, const Key &akey, const T &avalue, Node **anex
 template <class Key, class T>
 Q_INLINE_TEMPLATE QHash<Key, T> &QHash<Key, T>::unite(const QHash &other)
 {
-    QHash copy(other);
-    const_iterator it = copy.constEnd();
-    while (it != copy.constBegin()) {
-        --it;
-        insertMulti(it.key(), it.value());
+    if (d == &QHashData::shared_null) {
+        *this = other;
+    } else {
+        QHash copy(other);
+        const_iterator it = copy.constEnd();
+        while (it != copy.constBegin()) {
+            --it;
+            insertMulti(it.key(), it.value());
+        }
     }
     return *this;
 }
diff --git a/src/corelib/tools/qvector.h b/src/corelib/tools/qvector.h
index 13ae121450..806a127cc2 100644
--- a/src/corelib/tools/qvector.h
+++ b/src/corelib/tools/qvector.h
@@ -793,24 +793,28 @@ QVector<T> &QVector<T>::fill(const T &from, int asize)
 template <typename T>
 QVector<T> &QVector<T>::operator+=(const QVector &l)
 {
-    uint newSize = d->size + l.d->size;
-    const bool isTooSmall = newSize > d->alloc;
-    if (!isDetached() || isTooSmall) {
-        QArrayData::AllocationOptions opt(isTooSmall ? QArrayData::Grow : QArrayData::Default);
-        reallocData(d->size, isTooSmall ? newSize : d->alloc, opt);
-    }
+    if (d == Data::sharedNull()) {
+        *this = l;
+    } else {
+        uint newSize = d->size + l.d->size;
+        const bool isTooSmall = newSize > d->alloc;
+        if (!isDetached() || isTooSmall) {
+            QArrayData::AllocationOptions opt(isTooSmall ? QArrayData::Grow : QArrayData::Default);
+            reallocData(d->size, isTooSmall ? newSize : d->alloc, opt);
+        }
 
-    if (d->alloc) {
-        T *w = d->begin() + newSize;
-        T *i = l.d->end();
-        T *b = l.d->begin();
-        while (i != b) {
-            if (QTypeInfo<T>::isComplex)
-                new (--w) T(*--i);
-            else
-                *--w = *--i;
+        if (d->alloc) {
+            T *w = d->begin() + newSize;
+            T *i = l.d->end();
+            T *b = l.d->begin();
+            while (i != b) {
+                if (QTypeInfo<T>::isComplex)
+                    new (--w) T(*--i);
+                else
+                    *--w = *--i;
+            }
+            d->size = newSize;
         }
-        d->size = newSize;
     }
     return *this;
 }