CS 444/644 - Compiler Construction (Winter 2021) - Assignment 4

For the fourth assignment, you will implement static reachability analysis, and check that all variables have an initializer.

As in previous assignments, you must hand in to Marmoset a .zip archive containing your source code. The .zip file must contain a file called Makefile. Marmoset will run make on this Makefile to compile your compiler. The Makefile must generate an executable (binary or shell script) called joosc. The joosc executable must accept multiple filenames as arguments. All of the files listed on the joosc command line, and only those files, are considered part of the program being compiled.

Unlike javac and unlike the dOvs version of Joos, your joosc compiler should not look for classes in .class files on the CLASSPATH; it should read only the Joos 1W source files listed on the command line. This means that all classes, including classes such as java.lang.Object, must be available in source form and must be specified on the joosc command line. Unlike javac, Joos does not care what directory a source file is in (i.e. it does not require the directory structure of the source code to match the package structure). However, the class declared in a file must still have the same name as the filename. For example, Java would require that the class java.lang.Object be declared in the file Object.java in the directory java.lang, whereas Joos only requires the file to be named Object.java, but otherwise allows it to be in any directory.

For the purposes of this course, a minimalist version of the Java standard library is provided. This library can be found in the linux.student.cs environment in the directory /u/cs444/pub/stdlib/4.0. Marmoset will include all files in this library on the joosc command line for every test, in addition to other source file(s) specific to that test. The following versioning scheme is used to make it possible to correct errors and/or to extend the library for future assignments (although we aim to minimize the number of changes that will be required). The 4 in the directory name refers to Assignment 4, and the 0 is the first version of the library. Any corrections to the Assignment 4 version of the library will appear in the directories 4.1, 4.2, etc., and the version of the library for Assignment 5 will appear in the directory 5.0.

Version 4.0 of the standard library is identical to version 3.0.

As in previous assignments, joosc should process the Joos 1W files given on the command line, produce appropriate diagnostic messages on standard error, and exit with one of the following Unix return codes:

The Marmoset tests for this assignment take several minutes to run. Do not submit more than one submission at a time to Marmoset. If Marmoset reports that your previous submission has not been tested yet, do not submit another one. Denial-of-service attacks on Marmoset will result in disciplinary action.

Submit to Marmoset a PDF document of no more than six pages explaining the design decisions you made in completing Assignments 2, 3, and 4. As for Assignment 1, the document should be organized to enable someone unfamiliar with your code to understand the structure of your compiler. In the document, discuss challenges that you encountered and how you tried to overcome them in your design and implementation. Also explain the testing that you did before submitting to Marmoset.

The document will be hand-marked, with 50% of the marks for organization, clarity, and style, and 50% of the marks for technical content.

According to the late policy posted on the course web page, design documents submitted after the assignment deadline will not be marked and will receive a mark of zero. If you cannot finish the assignment by the deadline, submit what you have by the deadline, and explain any unfinished parts in your design document.

Reachability Checking

This phase must check the following restrictions of the Joos 1W language: