The present invention relates a compiler program, a computer-readable storage medium storing such a compiler program, a compiling method and a compiling unit, and an object thereof is to automatically generate a reentrant object program. In order to accomplish this object, an address saving program generator 16a generates an address saving program for saving a data area address of a calling program module; an address setting program generator 16b generates an address setting program for setting a data area address of an other program module; a transferring program generator 16c generates a transferring program for the transfer from the calling program module to the other program module; an address resetting program generator 16d generates an address resetting program for reading and resetting the saved data area address; and an accessing program generator 16e generates an accessing program for accessing a data area for the other program module using a relative address from the set data area address.