Added template to the private classes to avoid double allocation in QVariant

1 files changed, 18 insertions, 7 deletions

diff --git a/src/corelib/kernel/qvariant_p.h b/src/corelib/kernel/qvariant_p.h
index 727a390..72c09ec 100644
--- a/src/corelib/kernel/qvariant_p.h
+++ b/src/corelib/kernel/qvariant_p.h
@@ -91,13 +91,25 @@ inline T *v_cast(QVariant::Private *d, T * = 0)
 
 #endif
 
+
+//a simple template that avoids to allocate 2 memory chunks when creating a QVariant
+template <class T> class QVariantPrivateSharedEx : public QVariant::PrivateShared
+{
+public:
+    QVariantPrivateSharedEx() : QVariant::PrivateShared(&m_t) { }
+    QVariantPrivateSharedEx(const T&t) : QVariant::PrivateShared(&m_t), m_t(t) { }
+
+private:
+    T m_t;
+};
+
 // constructs a new variant if copy is 0, otherwise copy-constructs
 template <class T>
 inline void v_construct(QVariant::Private *x, const void *copy, T * = 0)
 {
     if (sizeof(T) > sizeof(QVariant::Private::Data)) {
-        x->data.shared = copy ? new QVariant::PrivateShared(new T(*static_cast<const T *>(copy)))
-                              : new QVariant::PrivateShared(new T);
+        x->data.shared = copy ? new QVariantPrivateSharedEx<T>(*static_cast<const T *>(copy))
+                              : new QVariantPrivateSharedEx<T>;
         x->is_shared = true;
     } else {
         if (copy)
@@ -111,12 +123,11 @@ inline void v_construct(QVariant::Private *x, const void *copy, T * = 0)
 template <class T>
 inline void v_clear(QVariant::Private *d, T* = 0)
 {
-    if (sizeof(T) > sizeof(QVariant::Private::Data)) {
-        delete v_cast<T>(d);
+    //now we need to call the destructor in any case
+    //because QVariant::PrivateShared doesn't have a virtual destructor
+    v_cast<T>(d)->~T();
+    if (sizeof(T) > sizeof(QVariant::Private::Data))
         delete d->data.shared;
-    } else {
-        v_cast<T>(d)->~T();
-    }
 }
 
 QT_END_NAMESPACE