There are many places that call cast_to_oop with an argument of type "address" (which is equivalent to uint8_t*). There appears to be only one call (in a gtest) with an argument of type char*, and that place probably ought to be using "address". Reducing the number of supported types for cast_to/from_oop makes the code easier to understand and may simplify further cleanups, perhaps including explicit enumeration and limitation of the supported conversions.