QEasingCurve: simplify and fix copy constructor

The copy constructor used the default Private constructor,
followed by the application of the compiler-generated
copy assignment operator, and finally replaced the config
member with a copy of itself.

This is needlessly inefficient.

Worse: it's incorrect: if config->copy() throws, then
*d_ptr is leaked.

Solution: implement the copy constructor for Private,
and use it in the copy constructor of the public class.

Effect: everything that can throw now prevents the new
Private class from being created, and the compiler ends
up cleaning up after us.

Change-Id: I09ed18bb39ee7cd81aaa8ba01676fc202502a8e3
Reviewed-by: Lars Knoll <lars.knoll@nokia.com>

src/corelib/tools/qeasingcurve.cpp

@@ -419,6 +419,11 @@ public:
           config(0),
           func(&easeNone)
     { }
+    QEasingCurvePrivate(const QEasingCurvePrivate &other)
+        : type(other.type),
+          config(other.config ? other.config->copy() : 0),
+          func(other.func)
+    { }
     ~QEasingCurvePrivate() { delete config; }
     void setType_helper(QEasingCurve::Type);
 
@@ -1080,12 +1085,9 @@ QEasingCurve::QEasingCurve(Type type)
     Construct a copy of \a other.
  */
 QEasingCurve::QEasingCurve(const QEasingCurve &other)
-    : d_ptr(new QEasingCurvePrivate)
+    : d_ptr(new QEasingCurvePrivate(*other.d_ptr))
 {
     // ### non-atomic, requires malloc on shallow copy
-    *d_ptr = *other.d_ptr;
-    if (other.d_ptr->config)
-        d_ptr->config = other.d_ptr->config->copy();
 }
 
 /*!