-/* Type-checking macro to provide arguments for CoCreateInstance() etc.
- * The pointer arithmetic is a compile-time pointer type check that 'obj'
- * really is a 'type **', but is intended to have no effect at runtime. */
+/* Type-checking macro to provide arguments for CoCreateInstance()
+ * etc, ensuring that 'obj' really is a 'type **'. */
+#define typecheck(checkexpr, result) \
+ (sizeof(checkexpr) ? (result) : (result))