Accession Number : ADA309489

Title :   Practical Program Understanding with Type Inference.

Descriptive Note : Research rept.,

Corporate Author : CARNEGIE-MELLON UNIV PITTSBURGH PA DEPT OF COMPUTER SCIENCE

Personal Author(s) : O'Callahan, Robert ; Jackson, Daniel

PDF Url : ADA309489

Report Date : MAY 1996

Pagination or Media Count : 20

Abstract : Many questions that arise in the reverse engineering or restructuring of a program can be answered by determining, statically, where the structure of the program requires sets of variables to share a common representation. With this information we can find abstract data types, detect abstraction violations, identify unused variables, functions, and fields of data structures, detect simple errors of operations on abstract datatypes (such as failure to close after open), and locate sites of possible references to a value. We have a method for computing representation sharing by using types to encode representations. We use polymorphic type inference to compute new types for all variables, eliminating cases of incidental type sharing where the variables might have different representations. The method is fully automatic and smoothly integrates pointer aliasing and higher-order functions. Because it is fully modular and computationally inexpensive, it should scale to very large systems. We show how we used of a prototype tool to analyze Morphin, a 17,000 line robot control program written in C, answering a user's questions about program structure, detecting abstraction violations, and finding unused data structures and memory leaks.

Descriptors :   *COMPUTER PROGRAM VERIFICATION, *STRUCTURED PROGRAMMING, DATA BASES, ALGORITHMS, SOFTWARE ENGINEERING, ROBOTICS, DATA MANAGEMENT, STATISTICAL INFERENCE, SEMANTICS, INPUT OUTPUT PROCESSING, READ WRITE MEMORIES, SYSTEMS ANALYSIS, DYNAMIC PROGRAMMING, FIELDS(COMPUTER PROGRAMS), EXECUTIVE ROUTINES, CONTROL SEQUENCES, AUTOMATIC PROGRAMMING, C PROGRAMMING LANGUAGE.

Subject Categories : Computer Programming and Software

Distribution Statement : APPROVED FOR PUBLIC RELEASE