C to Java Transpiler (Mini Compiler)

📌 Project Overview

This project is a source-to-source compiler (transpiler) that reads a restricted subset of C language and generates an equivalent Java program.

The goal of this project is not to fully support C or Java, but to demonstrate a clear understanding of compiler design principles, including:

• Lexical Analysis
• Parsing
• Abstract Syntax Tree (AST) construction
• Semantic mapping between two programming languages
• Code generation

This project is developed as part of a Compiler Design course assignment.

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🎯 Objective

• Parse a .c file written in a restricted C syntax
• Translate its semantics into valid Java source code
• Preserve program behavior (control flow, logic, output)

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🏗️ Compiler Architecture

The transpiler follows a classic compiler pipeline:

C Source Code (.c)
        ↓
Lexical Analysis (Tokenizer)
        ↓
Parsing (AST Construction)
        ↓
Semantic Mapping (C → Java)
        ↓
Java Code Generation (.java)

Each stage is implemented explicitly to reflect real compiler design.

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✅ Supported C Features (MVP Scope)

The transpiler supports the following subset of C:

Data Types

• int
• float
• double
• char

Statements

• Variable declaration and initialization
• Assignment statements
• if / else / else if
• while loop
• for loop
• return

Expressions

• Arithmetic: + - * / %
• Relational: < > <= >= == !=
• Parenthesized expressions

I/O

• printf → mapped to System.out.print / System.out.println in Java

Program Structure

• A single main function
• No user-defined functions

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❌ Unsupported Features (Explicitly Out of Scope)

The following C features are not supported:

• Input (scanf)
• Pointers
• Arrays
• Structs / unions
• Header files (#include)
• Macros / preprocessor directives
• Dynamic memory (malloc, free)
• Function definitions (other than main)
• Function pointers

These limitations are intentional to keep the compiler focused and manageable.

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🧪 Test Program (FizzBuzz)

The following C program is used as the primary test case:

int main() {
    int n = 20;
    int i;

    for (i = 1; i <= n; i = i + 1) {
        if (i % 15 == 0) {
            printf("FizzBuzz\n");
        } else if (i % 3 == 0) {
            printf("Fizz\n");
        } else if (i % 5 == 0) {
            printf("Buzz\n");
        } else {
            printf("Number\n");
        }
    }

    return 0;
}

The generated Java code preserves:

• Control flow
• Arithmetic logic
• Output behavior

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🛠️ Implementation Language

• C++
• No external parser generators (e.g., Lex/Yacc)
• All compiler stages implemented manually for learning purposes

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📂 Project Structure (Planned)

c-to-java-transpiler/
│
├── lexer/          # Token definitions and tokenizer
├── parser/         # Grammar parsing and AST construction
├── ast/            # AST node definitions
├── semantic/       # C → Java semantic mapping
├── codegen/        # Java code generation
├── tests/          # Sample C input programs
├── output/         # Generated Java files
└── README.md

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🎓 Learning Outcomes

By completing this project, you will gain hands-on experience with:

• Writing a lexer and parser from scratch
• Designing and traversing an AST
• Understanding semantic differences between C and Java
• Building a real compiler pipeline
• Applying theoretical compiler design concepts practically

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🚀 Future Extensions (Optional)

• Support for arrays
• Basic function support
• Symbol table with type checking
• Error reporting and recovery
• LLVM IR or bytecode backend

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📜 Disclaimer

This project is educational and intentionally limited in scope. It is not intended to replace real-world compilers or transpilers.