ICL 2025 - LAB 5 - Static Typing of mini-C (in Java)

The goal of this lab is to implement the static typing of mini-C.

Typing rules are given in the accompanying PDF description.

Provided Code

The parser is already implemented: mini-c-java.tar.gz

It is important to read and understand the abstract syntax of mini-C, that is Pfile (parsed trees) and File (typed trees).

Once uncompressed (for instance with tar zxvf mini-c-java.tar.gz), you get a directory mini-c/. The library java-cup-11a-runtime.jar, provided in sub-directory lib/, must be added to the project (but recent versions of Eclipse and VSCode will do that automatically).

The provided code should compile out of the box. The main method is in file Main.java. It expects a file with extension .c on the command line, possibly with options --debug, --parse-only, and --type-only. If no file is given on the command line, the file test.c (included in the tarball) is used, to ease the tests.

If a lexical or syntax error is detected, it is reported and the program exits with code 1.

If the parsing is successful and option --parse-only is on the command line, then the program exits with code 0.

Lab Assignment

Implement the type checking in file Typing.java. This is a visitor that takes a value of type Pfile as input (a tree built by the parser, defined in Ptree.java) and builds a value of type File (the tree built by the type checker, defined in Ttree.java).

If a type error is detected, it is signaled using exception Error , with a suitable message string. This exception is caught in Main.java and displayed as

     error: ... your message here ...

and the program exits with code 1.

Indications

It is strongly advised to proceed step by step, with systematic testing. As a first goal, consider a C program as simple as

int main() { return 0; }

This means you only have to consider integer literals in expressions and return statements.

Tests

Some tests are provided in the /tests folder in the tar.gz file and where

C files organized in various categories:

  syntax/bad/    rejected at parsing
  syntax/good/   accepted at parsing
  typing/bad/    rejected at type checking
  typing/good/   accepted at type checking

run make typing-tests to run your compiler on these files. You should get the following:

> make typing-tests
javac -cp lib/java-cup-11a-runtime.jar -d bin src/mini_c/*.java
cd ./tests ; \
./test -2 ../mini-c
Testing of ../mini-c

11 states, 374 transitions, table size 1562 bytes
1401 additional bytes used for bindings

Part 2: Type-checking
bad .................................
good ......
Typing  : 39/39 : 100%

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