QVarLengthArray: fix appending an already-contained item

Like the lvalue QVector::append() overload, when we reallocate,
we need to take a copy of the function's argument because the
reference will get stale upon reallocation.

Add a test.

[ChangeLog][QtCore][QVarLengthArray] Fixed a bug involving
appending an item already in the container to the container
again.

Change-Id: I06eeed6cb383dd5924e47a302bb3d1666d04c8e8
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>

2 files changed, 30 insertions, 7 deletions

diff --git a/src/corelib/tools/qvarlengtharray.h b/src/corelib/tools/qvarlengtharray.h
index bb5ae78d2b..2d3c25a5dd 100644
--- a/src/corelib/tools/qvarlengtharray.h
+++ b/src/corelib/tools/qvarlengtharray.h
@@ -146,15 +146,25 @@ public:
     T value(int i, const T &defaultValue) const;
 
     inline void append(const T &t) {
-        if (s == a)   // i.e. s != 0
+        if (s == a) {   // i.e. s != 0
+            T copy(t);
             realloc(s, s<<1);
-        const int idx = s++;
-        if (QTypeInfo<T>::isComplex) {
-            new (ptr + idx) T(t);
+            const int idx = s++;
+            if (QTypeInfo<T>::isComplex) {
+                new (ptr + idx) T(std::move(copy));
+            } else {
+                ptr[idx] = std::move(copy);
+            }
         } else {
-            ptr[idx] = t;
+            const int idx = s++;
+            if (QTypeInfo<T>::isComplex) {
+                new (ptr + idx) T(t);
+            } else {
+                ptr[idx] = t;
+            }
         }
     }
+
     void append(const T *buf, int size);
     inline QVarLengthArray<T, Prealloc> &operator<<(const T &t)
     { append(t); return *this; }
diff --git a/tests/auto/corelib/tools/qvarlengtharray/tst_qvarlengtharray.cpp b/tests/auto/corelib/tools/qvarlengtharray/tst_qvarlengtharray.cpp
index 7fc44343a5..0806ad1318 100644
--- a/tests/auto/corelib/tools/qvarlengtharray/tst_qvarlengtharray.cpp
+++ b/tests/auto/corelib/tools/qvarlengtharray/tst_qvarlengtharray.cpp
@@ -77,8 +77,21 @@ struct Foo
 
 void tst_QVarLengthArray::append()
 {
-    QVarLengthArray<QString> v;
-    v.append(QString("hello"));
+    QVarLengthArray<QString, 2> v;
+    v.append(QString("1"));
+    v.append(v.front());
+    QCOMPARE(v.capacity(), 2);
+    // transition from prealloc to heap:
+    v.append(v.front());
+    QVERIFY(v.capacity() > 2);
+    QCOMPARE(v.front(), v.back());
+    while (v.size() < v.capacity())
+        v.push_back(v[0]);
+    QCOMPARE(v.back(), v.front());
+    QCOMPARE(v.size(), v.capacity());
+    // transition from heap to larger heap:
+    v.push_back(v.front());
+    QCOMPARE(v.back(), v.front());
 
     QVarLengthArray<int> v2; // rocket!
     v2.append(5);