QVarLengthArray: add rvalue overload of append/push_back

Improves performance when appending temporaries, esp. since
the aliasing fix in the lvalue overload in 0f730ef made that
overload correct, but a bit slower across reallocs.

The unit tests already also pass rvalues, so the function is
covered in the existing tests.

[ChangeLog][QtCore][QVarLengthArray] Added rvalue overloads
of append() and push_back().

Change-Id: If3a6970f03a160cba5b42d33d32d3d18948f6ce3
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>
Reviewed-by: Edward Welbourne <edward.welbourne@qt.io>

1 files changed, 28 insertions, 0 deletions

diff --git a/src/corelib/tools/qvarlengtharray.qdoc b/src/corelib/tools/qvarlengtharray.qdoc
index 5e53a969e8..127afcd069 100644
--- a/src/corelib/tools/qvarlengtharray.qdoc
+++ b/src/corelib/tools/qvarlengtharray.qdoc
@@ -303,6 +303,34 @@
 */
 
 /*!
+    \fn void QVarLengthArray::append(T &&t)
+    \overload append
+    \since 5.9
+
+    \note Unlike the lvalue overload of append(), passing a reference to
+    an object that is already an element of \c *this leads to undefined
+    behavior:
+
+    \code
+    vla.append(std::move(vla[0])); // BUG: passing an object that is already in the container
+    \endcode
+*/
+
+/*!
+    \fn void QVarLengthArray::push_back(T &&t)
+    \overload push_back
+    \since 5.9
+
+    \note Unlike the lvalue overload of push_back(), passing a reference to
+    an object that is already an element of \c *this leads to undefined
+    behavior:
+
+    \code
+    vla.push_back(std::move(vla[0])); // BUG: passing an object that is already in the container
+    \endcode
+*/
+
+/*!
     \fn inline void QVarLengthArray::removeLast()
     \since 4.5