+WXFARPROC s_wndprocRadioBtn = (WXFARPROC)NULL;
+
+// Hash allowing to find wxRadioBox containing the given radio button by its
+// HWND. This is used by (subclassed) radio button window proc to find the
+// radio box it belongs to.
+WX_DECLARE_HASH_MAP(HWND, wxRadioBox *,
+ wxPointerHash, wxPointerEqual,
+ RadioBoxFromButton);
+
+RadioBoxFromButton gs_boxFromButton;
+
+} // anonymous namespace