CI updates; cxxlib.h cleanups

src/util/util.h

@@ -128,8 +128,10 @@ forceinline void ptr_check_no_overlap(const void *a, size_t a_size, const void *
 // invalidate and poison a pointer: point to a non-null invalid address
 // - resulting pointer should crash on dereference
 // - this should be efficient, so no mmap() guard page etc.
-// - this should play nice with runtime checkers like ASAN, MSAN, valgrind, etc.
+// - this should play nice with runtime checkers like ASAN, MSAN, UBSAN, valgrind, etc.
 // - this should play nice with static analyzers like clang-tidy etc.
+// NOTE: this is clearly UB (Undefined Behaviour), and stricter compilers or
+//   architectures may need a more advanced/costly implementation in the future
 template <class T>
 inline void ptr_invalidate_and_poison(T *(&ptr)) noexcept {
     ptr = (T *) (void *) 251; // 0x000000fb // NOLINT(performance-no-int-to-ptr)