pyc99 0.1.1

Educational C99 compiler written in Python - compiles C to x86/ARM assembly

C99 Compiler

An educational C99 compiler written in Python, demonstrating compiler construction principles and C language implementation.

Features

• Full C99 Support: Implements most C99 language features including:

  • All primitive types (int, char, float, double, void)
  • Pointers, arrays, and multi-dimensional arrays
  • Structs, unions, and enums
  • Function pointers and variadic functions
  • Type qualifiers (const, volatile, restrict)
  • Storage classes (static, extern, auto, register)
  • Preprocessor directives (#define, #include, #ifdef, etc.)

• Multiple Target Architectures:

  • x86-64 (Intel and AT&T syntax)
  • ARM (32-bit and 64-bit)

• Comprehensive Testing: 1100+ test cases covering:

  • C99 conformance tests
  • Real-world program compilation
  • Integration tests
  • Unit tests for all compiler phases

Project Structure

.
├── src/
│   ├── lexer/          # Tokenization and lexical analysis
│   ├── parser/         # Syntax analysis and AST construction
│   ├── preprocessor/   # C preprocessor implementation
│   ├── semantic/       # Semantic analysis and type checking
│   ├── ir/             # Intermediate representation
│   ├── codegen/        # Code generation for target architectures
│   │   ├── x86/        # x86-64 code generator
│   │   └── arm/        # ARM code generator
│   └── utils/          # Utility functions and error reporting
├── tests/
│   ├── conformance/    # C99 conformance tests
│   ├── integration/    # End-to-end integration tests
│   └── unit/           # Unit tests for individual components
└── examples/           # Example C programs

Installation

From PyPI (Recommended)

pip install pyc99

From Source

# Clone the repository
git clone https://github.com/scobi84/pyc99.git
cd pyc99

# Install in development mode
pip install -e .

# Or install with development dependencies
pip install -e ".[dev]"

Requirements

• Python 3.11 or higher
• click library (installed automatically)

Usage

Compiling a C Program

# Compile to x86-64 assembly
pyc99 input.c -S -o output.s

# Compile for ARM
pyc99 input.c -S -t arm -o output.s

# Compile to object file
pyc99 input.c -c -o output.o

# Compile and link to executable (requires system assembler/linker)
pyc99 input.c -o program

# Compile multiple files
pyc99 main.c utils.c helpers.c -o program

# With optimization
pyc99 input.c -O1 -o program

# Verbose output
pyc99 input.c -v -o program

Command Line Options

Usage: pyc99 [OPTIONS] SOURCE_FILES...

Options:
  -t, --target [x86|arm]          Target architecture (default: x86)
  -o, --output PATH               Output file name
  -O, --optimization [0|1]        Optimization level (default: 0)
  -S, --assembly-only             Generate assembly only
  -c, --compile-only              Generate object file only
  -I, --include PATH              Add include search path
  -v, --verbose                   Verbose output
  -d, --debug                     Debug output
  --stop-after [preprocess|lex|parse|semantic|ir|optimize|codegen]
                                  Stop after specified phase
  --help                          Show this message and exit

Running Tests

# Run all tests
python3 -m pytest tests/

# Run specific test categories
python3 -m pytest tests/conformance/     # C99 conformance tests
python3 -m pytest tests/integration/     # Integration tests
python3 -m pytest tests/unit/            # Unit tests

# Run with verbose output
python3 -m pytest tests/ -v

# Run specific test file
python3 -m pytest tests/conformance/test_c99_expressions.py

Examples

See the examples/ directory for sample C programs:

• hello_world.c - Basic hello world
• fibonacci.c - Recursive Fibonacci
• struct_example.c - Struct usage
• pointer_example.c - Pointer manipulation
• And many more...

C99 Compliance

The compiler implements approximately 95% of the C99 standard. See C99_COMPLIANCE_ROADMAP.md for detailed feature coverage.

Implemented Features

✅ All basic types and type qualifiers ✅ Pointers, arrays, and pointer arithmetic ✅ Structs, unions, and enums ✅ Function declarations and definitions ✅ Control flow (if, while, for, switch, etc.) ✅ Operators and expressions ✅ Preprocessor directives ✅ Type casting and conversions ✅ Function pointers ✅ Variadic functions ✅ Inline functions ✅ Compound literals ✅ Designated initializers

Known Limitations

• Variable-length arrays (VLA) - partial support
• Some complex declarator combinations
• _Complex and _Imaginary types not implemented
• Some edge cases in type compatibility

Architecture

The compiler follows a traditional multi-pass architecture:

1. Preprocessing: Handles #include, #define, conditional compilation
2. Lexical Analysis: Tokenizes source code
3. Parsing: Builds Abstract Syntax Tree (AST)
4. Semantic Analysis: Type checking, symbol resolution
5. IR Generation: Converts AST to intermediate representation
6. Code Generation: Emits target assembly code

Development

Running Individual Compiler Phases

from src.lexer.tokenizer import Tokenizer
from src.parser.parser import Parser
from src.semantic.analyzer import SemanticAnalyzer

# Tokenize
tokenizer = Tokenizer(source_code, "file.c")

# Parse
parser = Parser(tokenizer)
ast = parser.parse_translation_unit()

# Semantic analysis
from src.utils.error_reporter import ErrorReporter
error_reporter = ErrorReporter()
analyzer = SemanticAnalyzer(ast, error_reporter)
analyzer.analyze()

Contributing

This is an educational project demonstrating compiler construction. Feel free to:

• Report bugs or issues
• Suggest improvements
• Add more test cases
• Improve documentation

License

Educational/Academic use

Acknowledgments

Built as an educational project to demonstrate:

• Compiler design and implementation
• C language semantics
• Code generation techniques
• Software testing practices