Mini-Java-Compiler

Author @hamza-mahjoub

About the project

A compiler for the following mini java BNF grammar

Program ::= MainClass ( ClassDeclaration )* <EOF>

MainClass ::= "class" Identifier "{" "public" "static" "void" "main" "(" "String" "[" "]" Identifier ")" "{" Statement "}" "}"

ClassDeclaration ::= "class" Identifier ( "extends" Identifier )? "{" ( VarDeclaration )* ( MethodDeclaration )*  "}"

VarDeclaration ::= Type Identifier ";"

MethodDeclaration ::= "public" Type Identifier "(" ( Type Identifier ( "," Type Identifier )* )? ")" "{" ( VarDeclaration )* ( Statement )* "return" Expression ";" "}"

Type ::= "int" "[" "]"
 | "boolean"
 | "int"
 | Identifier

Statement ::= "{" ( Statement )* "}"

 | "if" "(" Expression ")" Statement "else" Statement

 | "while" "(" Expression ")" Statement

 | "System.out.println" "(" Expression ")" ";"

 | Identifier "=" Expression ";"

 | Identifier "[" Expression "]" "=" Expression ";"

Expression ::= Expression ( "&&" | "<" | "+" | "-" | "*" ) Expression

 | Expression "[" Expression "]"

 | Expression "." "length"

 | Expression "." Identifier "(" ( Expression ( "," Expression )* )? ")"

 | <INTEGER_LITERAL>
 | <BOOLEAN_LITERAL>

 | Identifier

 | "this"
 | "new" "int" "[" Expression "]"

 | "new" Identifier "(" ")"

 | "!" Expression

 | "(" Expression ")"

Identifier ::= <IDENTIFIER>

Where

• identifier follows the regex expression ? /([A-Za-z_][A-Za-z0-9_]*)/ ?
• <INTEGER_LITERAL> follows the regex expression ? /(-?[1-9][0-9]*)/ ?
• <BOOLEAN_LITERAL> follows the regex expression = ? /(true|false)/ ?

Technologies

• Flex
• Bison
• C language

Project files

• LexicalAnalyzer.lex handles the text parsing and tokens generation.
• SyntaxAnalyzer.y handles syntax errors and invokes C functions that handles the semantic logic.
• symtab.h contains semantic C functions declaration.
• symtab.c contains semantic C functions implementation.
• CodeGeneration.h contains assembly C functions declaration.
• CodeGeneration.c contains assembly C functions implementation.

Get started

Generating app.exe

Generate the app.exe by running the following python script:

import os

os.system("flex LexicalAnalyzer.lex")
os.system("bison -d SyntaxAnalyzer.y")
os.system("gcc -o app SyntaxAnalyzer.tab.c lex.yy.c symtab.c codeGenerator.c")

then in cmd

python script.py

How to use the generated app.exe

Lets consider this test code:

/* ===========================================================
  CECI EST UN COMMENTAIRE qui prendra fin a la prochaine
  accolade fermante

  TP1 - ift2030 - automne 2002
  ============================================================ */

class Calculator {

  public static void main(String[] a) {
    System.out.println(new Calculator1().calculate());
  }
}

/* ====================================================
   Classe Calculator1
   ==================================================== */

class Calculator1 {

  bool test; // @ 0
  int somme; // @ 1

  public int calculate() {
    int x; // @ 2
    int y; // @ 3
    x = 5;
    y = 6;
    somme = x * 10;
    y = somme + 15;
    somme = x / y;

    if (x < 1) y = 1; else {
      x = x + 1;
      while (x > somme) y = y + 1;
    }

    return x;
  }
}

Use it as input for the generated app.exe:

app.exe < test.txt