The same code will not necessarily work. 32 bit devices usually need 32 bit pointers, and do not always have a 16 bit pointer mode. If you have the same settings for both devices, you might be storing pointers into 16 bits, and that might fail.
It is often possible to write C code that can be compiled for 16 or 32 bits, by careful use of data types, and by using a macro or compiler option to indicate which size to compile for the target.
