A case study in software portability

摘要

The widespread use of high-level languages and portable operating systems such as the UNIX operating system has greatly facilitated the development of portable utilities and application programs. The activity of "porting" software from one environment to another differs from both maintenance and implementation activities and raises a different set of considerations. This paper discusses the porting of the UNIX symbolic debugger (SDB) from the VAX 11/780 to the M68000 based EXORmacs® development system. This was done as part of the first complete AT&T-sanctioned UNIX System V port which was performed by Motorola Microsystems. We first present a brief discussion of the objectives and methods of the UNIX port in which we participated, followed by a short description of the functionality and operation of SDB. We then describe some of the most significant problems as well as our most useful techniques for porting this highly machine-dependent utility. It is argued that there are reallytwo distinct types of software portability problems, namely host dependencies and target dependencies and that the difference between this two is often obscured. We conclude with several recommendations for building more portability into a program such as a symbolic debugger.