QVarLengthArray: Add initializer_list constructor

Implement an initializer_list constructor, which was probably
just forgotten so far. Technically this is a SC incompatible change,
since

  QVarLengthArray<int> array = {10};

will now create an array with one element 10, instead of an empty array
with a reserved size of 10. Anyhow, keeping the inconsistency with the
STL / other Qt containers here would certainly do more harm than good
in the long run.

Task-number: QTBUG-45047
Change-Id: I4675880f93e141181250939942fa32300916b0e3
Reviewed-by: Marc Mutz <marc.mutz@kdab.com>

src/corelib/tools/qvarlengtharray.h

@@ -42,6 +42,9 @@
 #include <string.h>
 #include <stdlib.h>
 #include <algorithm>
+#ifdef Q_COMPILER_INITIALIZER_LISTS
+#include <initializer_list>
+#endif
 
 QT_BEGIN_NAMESPACE
 
@@ -62,6 +65,14 @@ public:
         append(other.constData(), other.size());
     }
 
+#ifdef Q_COMPILER_INITIALIZER_LISTS
+    QVarLengthArray(std::initializer_list<T> args)
+        : a(Prealloc), s(0), ptr(reinterpret_cast<T *>(array))
+    {
+        append(args.begin(), args.size());
+    }
+#endif
+
     inline ~QVarLengthArray() {
         if (QTypeInfo<T>::isComplex) {
             T *i = ptr + s;

src/corelib/tools/qvarlengtharray.qdoc

@@ -100,6 +100,17 @@
     \l{default-constructed value}.
 */
 
+
+/*! \fn QVarLengthArray::QVarLengthArray(std::initializer_list<T> args)
+    \since 5.5
+
+    Constructs an array from the std::initializer_list given by \a args.
+
+    This constructor is only enabled if the compiler supports C++11 initializer
+    lists.
+*/
+
+
 /*! \fn QVarLengthArray::~QVarLengthArray()
 
     Destroys the array.

tests/auto/corelib/tools/qvarlengtharray/tst_qvarlengtharray.cpp

@@ -54,6 +54,12 @@ private slots:
     void indexOf();
     void lastIndexOf();
     void contains();
+    void initializeListInt();
+    void initializeListMovable();
+    void initializeListComplex();
+private:
+    template<typename T>
+    void initializeList();
 };
 
 int fooCtor = 0;
@@ -333,11 +339,23 @@ struct MyPrimitive
 struct MyMovable
     : MyBase
 {
+    MyMovable(char input = 'j') : i(input) {}
+    bool operator==(const MyMovable &other) const
+    {
+        return i == other.i;
+    }
+    char i;
 };
 
 struct MyComplex
     : MyBase
 {
+    MyComplex(char input = 'j') : i(input) {}
+    bool operator==(const MyComplex &other) const
+    {
+        return i == other.i;
+    }
+    char i;
 };
 
 QT_BEGIN_NAMESPACE
@@ -734,5 +752,49 @@ void tst_QVarLengthArray::contains()
     QVERIFY(myvec.contains(QLatin1String("I don't exist")));
 }
 
+void tst_QVarLengthArray::initializeListInt()
+{
+    initializeList<int>();
+}
+
+void tst_QVarLengthArray::initializeListMovable()
+{
+    const int instancesCount = MyMovable::liveCount;
+    initializeList<MyMovable>();
+    QCOMPARE(MyMovable::liveCount, instancesCount);
+}
+
+void tst_QVarLengthArray::initializeListComplex()
+{
+    const int instancesCount = MyComplex::liveCount;
+    initializeList<MyComplex>();
+    QCOMPARE(MyComplex::liveCount, instancesCount);
+}
+
+template<typename T>
+void tst_QVarLengthArray::initializeList()
+{
+#ifdef Q_COMPILER_INITIALIZER_LISTS
+    T val1(110);
+    T val2(105);
+    T val3(101);
+    T val4(114);
+
+    QVarLengthArray<T> v1 {val1, val2, val3};
+    QCOMPARE(v1, QVarLengthArray<T>() << val1 << val2 << val3);
+    QCOMPARE(v1, (QVarLengthArray<T> {val1, val2, val3}));
+
+    QVarLengthArray<QVarLengthArray<T>, 4> v2{ v1, {val4}, QVarLengthArray<T>(), {val1, val2, val3} };
+    QVarLengthArray<QVarLengthArray<T>, 4> v3;
+    v3 << v1 << (QVarLengthArray<T>() << val4) << QVarLengthArray<T>() << v1;
+    QCOMPARE(v3, v2);
+
+    QVarLengthArray<T> v4({});
+    QCOMPARE(v4.size(), 0);
+#else
+    QSKIP("This tests requires a compiler that supports initializer lists.");
+#endif
+}
+
 QTEST_APPLESS_MAIN(tst_QVarLengthArray)
 #include "tst_qvarlengtharray.moc"