QFlagPointer/QBiPointer: insert static assertions in addition to dynamic

Static assertions weren't really a thing back in 2012 when Aaron wrote
this code.

Change-Id: I8d95fbaf90e842b9b44dfffd15cde4c154e22810
Reviewed-by: Ulf Hermann <ulf.hermann@qt.io>
Reviewed-by: Fabian Kosmale <fabian.kosmale@qt.io>

1 files changed, 16 insertions, 0 deletions

diff --git a/src/qml/qml/ftw/qflagpointer_p.h b/src/qml/qml/ftw/qflagpointer_p.h
index 71b41cd30b..a10e57aeca 100644
--- a/src/qml/qml/ftw/qflagpointer_p.h
+++ b/src/qml/qml/ftw/qflagpointer_p.h
@@ -55,6 +55,17 @@
 
 QT_BEGIN_NAMESPACE
 
+namespace QtPrivate {
+template <typename T> struct QFlagPointerAlignment
+{
+    enum : size_t { Value = Q_ALIGNOF(T) };
+};
+template <> struct QFlagPointerAlignment<void>
+{
+    enum : size_t { Value = ~size_t(0) };
+};
+}
+
 template<typename T>
 class QFlagPointer {
 public:
@@ -133,6 +144,7 @@ template<typename T>
 QFlagPointer<T>::QFlagPointer(T *v)
 : ptr_value(quintptr(v))
 {
+    Q_STATIC_ASSERT_X(Q_ALIGNOF(T) >= 4, "Type T does not have sufficient alignment");
     Q_ASSERT((ptr_value & FlagsMask) == 0);
 }
 
@@ -247,6 +259,8 @@ template<typename T, typename T2>
 QBiPointer<T, T2>::QBiPointer(T *v)
 : ptr_value(quintptr(v))
 {
+    Q_STATIC_ASSERT_X(QtPrivate::QFlagPointerAlignment<T>::Value >= 4,
+                      "Type T does not have sufficient alignment");
     Q_ASSERT((quintptr(v) & FlagsMask) == 0);
 }
 
@@ -254,6 +268,8 @@ template<typename T, typename T2>
 QBiPointer<T, T2>::QBiPointer(T2 *v)
 : ptr_value(quintptr(v) | Flag2Bit)
 {
+    Q_STATIC_ASSERT_X(QtPrivate::QFlagPointerAlignment<T2>::Value >= 4,
+                      "Type T2 does not have sufficient alignment");
     Q_ASSERT((quintptr(v) & FlagsMask) == 0);
 }