_q_interpolate<T> is unsafe with unsigned template arguments

_q_interpolate<T> subtracts 2 arguments of type T,
for unsigned types this can cause wrapping around

Task-number: QTBUG-57925
Change-Id: Iffa59f413579a3d5de8cb728fe71443d8e8a04aa
Reviewed-by: Giuseppe D'Angelo <giuseppe.dangelo@kdab.com>

1 files changed, 13 insertions, 1 deletions

diff --git a/src/corelib/animation/qvariantanimation_p.h b/src/corelib/animation/qvariantanimation_p.h
index 37318a5339..9f0f2e3030 100644
--- a/src/corelib/animation/qvariantanimation_p.h
+++ b/src/corelib/animation/qvariantanimation_p.h
@@ -58,6 +58,8 @@
 
 #include "private/qabstractanimation_p.h"
 
+#include <type_traits>
+
 #ifndef QT_NO_ANIMATION
 
 QT_BEGIN_NAMESPACE
@@ -104,7 +106,17 @@ public:
 };
 
 //this should make the interpolation faster
-template<typename T> inline T _q_interpolate(const T &f, const T &t, qreal progress)
+template<typename T>
+typename std::enable_if<std::is_unsigned<T>::value, T>::type
+_q_interpolate(const T &f, const T &t, qreal progress)
+{
+    return T(f + t * progress - f * progress);
+}
+
+// the below will apply also to all non-arithmetic types
+template<typename T>
+typename std::enable_if<!std::is_unsigned<T>::value, T>::type
+_q_interpolate(const T &f, const T &t, qreal progress)
 {
     return T(f + (t - f) * progress);
 }