javar

A Java Compiler written in Java. It currently can compile simple Java programs to MIPS assembly format.

Building

Dependencies

• jdk9
• JavaCC 7.0.3
  • Note: This is only needed if the parser files need to be re-generated

IDE

Recommended: IntelliJ IDEA

Whille using an IDE, you can build and run by simply pressing "Run".

Build from command line

javac -d out -cp src/ src/Main.java

Usage

java -cp out Main --mips [inputfiles]

inputfiles is a space-separated list of at least one file path. The path can be absolute or relative to the current directory.

Available Target Architectures

• MIPS

Generating Parser using JavaCC

Usage

javacc -OUTPUT_DIRECTORY=src/frontend/parse/ src/frontend/parse/JavarParser.jj

Issues with javacc

Since 6.0, the advertised javacc script is not packaged in binaries. You will need to add the following script in javacc-7.x.x/target/ after building:

#!/bin/sh
JAR="`dirname $0`/javacc.jar"

case "`uname`" in
     CYGWIN*) JAR="`cygpath --windows -- "$JAR"`" ;;
esac

java -classpath "$JAR" javacc "$@"

Note: Make sure that the JAR variable points to the correct location of the javacc.jar file.

Features

TODO

Current Plans

• Refactoring:
  • Upgrade code to incorporate Java 8 features
  • Implement stream api as much as possible
  • Make all fields private/protected (encapsulation)
  • Make appropiate fields static/final (enforce immutability)
  • Implement visitor pattern for assem stage
  • Merge AST node classes for different stages where applicable
• Phase out JavaCC, adapt current generated parser logic into one that we manage directly
  • NOTE: if this is too difficult, implement a recursive descent parser, but that will take a lot of time

Future Plans

• Implement interpreter until we have a solid architecture implementation (hard to run MIPS on a non-MIPS machine)
• Implement modules off of ECMAScript 6 standard (this will be the first deviation from actual Java)
  • Change CLI to only allow one file as input
• Implement static methods
• Support void methods
• Implement dynamically determined entry point (look for a static main method in the specified class)
• Write to a file instead of stdout
• Implement more exceptions
  • ArithmeticException
  • ClassCastException
  • ClassNotFoundException
  • NegativeArraySizeException
• Expand grammar
  • Expressions on the left hand side
• Support threading/concurrency

Known Issues