CS 444/644 - Compiler Construction (Winter 2026) - Assignment 4

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

Reachability Checking

• All statements must be reachable. Details of the exact definition of reachability are specified in Section 14.20 of the Java Language Specification.
• The last statement on every finite-length execution path through a method whose return type is not void must be a return statement.
• Every local variable must have an initializer, and the variable must not occur in its own initializer.

Code Submission

Submit to Marmoset a .zip archive containing everything required to build and run your project. It should also include all your test cases and test code that you used to test your compiler. It must also include a file named git.log showing the commit history of your Git repository.

In addition to the above, the .zip file should contain a file named Makefile in the root directory. Marmoset will run make on this Makefile to build your compiler. The Makefile must generate an executable (binary or shell script) called joosc.

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:

• 0: the input file is valid Joos 1W
• 42: the input file is not valid Joos 1W
• any other value: your compiler crashed

Your build process and execution of joosc should not send or receive data from/to the internet in any way.

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.

Document Submission

Submit to Marmoset a PDF document explaining the design decisions you made in completing Assignments 2, 3, and 4. The document will be evaluated based on both writing and technical content. Good writing often reflects good thinking. Be clear, thorough, and concise.

The document should be no more than six letter-sized pages long, should use a 10-12 point font, and should use reasonable margins and line spacing. It should have a title and should list the names and WatIAM (Quest) userids of the group members.

Documents submitted after the assignment deadline will not be marked and will receive a mark of zero. If you cannot finish the implementation by the deadline, document what you have by the deadline, and explain any unfinished parts in your document.

The document should typically cover the following topics:

Design and Implementation

This should be the main part of your document. Things to consider:

• Organization of your compiler
• Design patterns, special data structures and algorithms, libraries
• Trade-offs you made between conflicting design goals (e.g., code simplicity vs. performance)
• Challenges you ran into and how you addressed them
• Any other noteworthy aspects of your design and implementation

Your goal is to enable someone unfamiliar with your compiler to understand it (without looking at the source code) and to convince the course staff that you have thought carefully about the construction of your compiler.

Testing and Known issues

Describe your test cases and the result of testing. Detail any known issues of your compiler. Your compiler will be evaluated on secret Marmoset tests at the end of the term, so you want to achieve good coverage of the input space and of your code in your own tests.

Contributions

Describe what each group member did.

Thoughts

• How much time did you spend on the assignments? What did you like or dislike about the assignments? What would you change about them?
• What aspects of your chosen programming language did you find helpful in writing the compiler? What aspects caused annoyance?
• Any other thoughts?

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