Created attachment 404135 [details] Output running WebKitGTK under Clang/UBSAN from Evolution I managed to compile WebKitGTK 2.28.3 under Clang/UBSAN (to a certain extend). WebKitGTK is used by Gnome Evolution and when it runs, it prints a lot of undefined behaviour notices, as can be seen from the attached file. See also https://gitlab.gnome.org/GNOME/evolution/-/issues/1023.