Our problem statement is to design and implement a compiler for a simple programming C++-like language using the Lex and Yacc compiler generating packages and a simple GUI using C++.

This project for a Mini Compiler for the C++ programming language was made for the course title Compiler Design. The project focuses on generating an intermediate code for the language for specific constructs. It works for constructs such as conditional statements, loops, and the ternary operator. The main functionality of the project is to generate an optimized intermediate code for the given C++ source code. This is done using the following steps:

• Generate symbol table after performing expression evaluation
• Generate Abstract Syntax Tree for the code
• Generate 3 address code followed by corresponding quadruples
• Perform Code Optimization

The main tools used in the project include LEX which identifies predefined patterns and generates tokens for the patterns matched and YACC which parses the input for semantic meaning and generates an abstract syntax tree and intermediate code for the source code. PYTHON is used to optimize the intermediate code generated by the parser.

In our symbol table, we have handled error detection as well as expression evaluation. We have also covered handling undeclared variables, detecting redeclaration of variables, and syntax errors like semicolon missing.

Intermediate code generator receives input from its predecessor phase, semantic analyser, in the form of an annotated syntax tree. That syntax tree then can be converted into a linear representation. Intermediate code tends to be machine independent code.

The code optimizer maintains a key-value mapping that resembles the symbol table structure to keep track of variables and their values (possibly after expression evaluation). This structure is used to perform constant propagation and constant folding in sequential blocks followed by dead code elimination.

As part of our syntax validation, we have made use of an abstract syntax tree. Abstract syntax trees are data structures widely used in compilers to represent the structure of program code. An AST is usually the result of the syntax analysis phase of a compiler. It often serves as an intermediate representation of the program through several stages that the compiler requires, and has a strong impact on the final output of the compiler. Here, our tree that is representing the syntactic flow of our code is generated. We have made use of %left and %right fields (types of grammar symbols) We made use of the AST so that we can separate the parsing and validation logic from the implementation piece. We used the AST as part of our syntax validation phase so that when there is a problem parsing some strange syntax you can just look at the AST parser, where if a piece of code is not producing the expected results than you look at the code that interprets the AST.

1. Sunad Suhas
2. Eshan Naik
3. Ishita Datta