Java Binary Compatibility Is Almost Correct Version 2

The Java language description is unusual in that it de nes the e ect of interleaving separate compilation and source code modi cations. In Java, certain source code modi cations, such as adding a method to a class, are de ned as binary compatible. The Java language description does not require the re-compilation of programs importing classes or interfaces which were modi ed in binary compatible ways, and it claims that successful linking and execution of the altered program is guaranteed. In this paper we show that Java binary compatibility does not actually guarantee successful linking and execution. We then suggest a framework in which we formalize the requirement of safe linking and execution without re-compilation and we propose a more modest de nition of binary compatibility. We prove for a substantial subset of Java, that our de nition guarantees safe linking and execution.