1 files changed, 27 insertions, 30 deletions

diff --git a/src/corelib/tools/qvector.h b/src/corelib/tools/qvector.h
index 288c082c44..85393a3598 100644
--- a/src/corelib/tools/qvector.h
+++ b/src/corelib/tools/qvector.h
@@ -337,20 +337,14 @@ QVector(InputIterator, InputIterator) -> QVector<ValueType>;
 // behavior change: an object of POD type constructed with an initializer of the form ()
 // will be default-initialized
 #   pragma warning ( push )
-#   pragma warning ( disable : 4345 )
 #   pragma warning(disable : 4127) // conditional expression is constant
 #endif
 
 template <typename T>
 void QVector<T>::defaultConstruct(T *from, T *to)
 {
-    if (QTypeInfo<T>::isComplex) {
-        while (from != to) {
-            new (from++) T();
-        }
-    } else {
-        ::memset(static_cast<void *>(from), 0, (to - from) * sizeof(T));
-    }
+    while (from != to)
+        new (from++) T();
 }
 
 template <typename T>
@@ -529,7 +523,7 @@ QVector<T>::QVector(int asize, const T &t)
         d = Data::allocate(asize);
         Q_CHECK_PTR(d);
         d->size = asize;
-        T* i = d->end();
+        auto i = d->end();
         while (i != d->begin())
             new (--i) T(t);
     } else {
@@ -641,17 +635,13 @@ void QVector<T>::reallocData(const int asize, const int aalloc, QArrayData::Allo
 
                 if (asize > d->size) {
                     // construct all new objects when growing
-                    if (!QTypeInfo<T>::isComplex) {
-                        ::memset(static_cast<void *>(dst), 0, (static_cast<T *>(x->end()) - dst) * sizeof(T));
-                    } else {
-                        QT_TRY {
-                            while (dst != x->end())
-                                new (dst++) T();
-                        } QT_CATCH (...) {
-                            // destruct already copied objects
-                            destruct(x->begin(), dst);
-                            QT_RETHROW;
-                        }
+                    QT_TRY {
+                        while (dst != x->end())
+                            new (dst++) T();
+                    } QT_CATCH (...) {
+                        // destruct already copied objects
+                        destruct(x->begin(), dst);
+                        QT_RETHROW;
                     }
                 }
             } QT_CATCH (...) {
@@ -845,18 +835,25 @@ typename QVector<T>::iterator QVector<T>::insert(iterator before, size_type n, c
         if (!isDetached() || d->size + n > int(d->alloc))
             realloc(d->size + n, QArrayData::Grow);
         if (!QTypeInfoQuery<T>::isRelocatable) {
-            T *b = d->end();
-            T *i = d->end() + n;
-            while (i != b)
-                new (--i) T;
-            i = d->end();
+            T *const e = d->end();
+            T *const b = d->begin() + offset;
+
+            T *i = e;
             T *j = i + n;
-            b = d->begin() + offset;
-            while (i != b)
-                *--j = *--i;
-            i = b+n;
+
+            // move old elements into the uninitialized space
+            while (i != b && j > e)
+                new (--j) T(std::move(*--i));
+            // move the rest of old elements into the tail using assignment
             while (i != b)
-                *--i = copy;
+                *--j = std::move(*--i);
+
+            // construct copies of t inside the uninitialized space
+            while (j != b && j > e)
+                new (--j) T(copy);
+            // use assignment to fill the recently-moved-from space
+            while (j != b)
+                *--j = copy;
         } else {
             T *b = d->begin() + offset;
             T *i = b + n;