QVLA: Add operator= for initializer lists

Add a dedicated operator=(std::initializer_list) that
first resizes the QCLA, and then replaces the elements
one by one.

This should be usually faster than creating a temporary
QCLA and then copying it, except for the case where the
new array does not fit into the allocated stack - but this
is IMO nothing to optimize for.

Task-number: QTBUG-45041
Change-Id: I147d6d01186b1ca3c635b2c8365d8f6e638ce6fe
GPush-Base: 08de3113051e1289f0de0651ec5647c9ee6feb27
Reviewed-by: Marc Mutz <marc.mutz@kdab.com>
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>

1 files changed, 9 insertions, 0 deletions

diff --git a/src/corelib/tools/qvarlengtharray.h b/src/corelib/tools/qvarlengtharray.h
index 95cd0447d8..90b54b7297 100644
--- a/src/corelib/tools/qvarlengtharray.h
+++ b/src/corelib/tools/qvarlengtharray.h
@@ -91,6 +91,15 @@ public:
         return *this;
     }
 
+#ifdef Q_COMPILER_INITIALIZER_LISTS
+    QVarLengthArray<T, Prealloc> &operator=(std::initializer_list<T> list)
+    {
+        resize(list.size());
+        std::copy(list.begin(), list.end(), this->begin());
+        return *this;
+    }
+#endif
+
     inline void removeLast() {
         Q_ASSERT(s > 0);
         realloc(s - 1, a);