Project 10: Modular Program Architecture

A well-structured multi-file C program demonstrating opaque types, header organization, linkage control, and professional build automation.

Quick Reference

Attribute Value
Primary Language C
Alternative Languages None
Difficulty Level 3 - Advanced
Time Estimate See main guide
Knowledge Area Software Architecture, Build Systems
Tooling GCC, Make, CMake
Prerequisites See main guide

What You Will Build

A well-structured multi-file C program demonstrating opaque types, header organization, linkage control, and professional build automation.

Why It Matters

This project builds core skills that appear repeatedly in real-world systems and tooling.

Core Challenges

  • Header organization → Maps to preventing compilation errors
  • Opaque types → Maps to information hiding
  • Build automation → Maps to reproducible builds

Key Concepts

  • Map the project to core concepts before you code.

Real-World Outcome

# 1. Project structure
$ tree
.
├── include/
│   ├── mylib/
│   │   ├── buffer.h      # Public API - opaque type
│   │   ├── list.h        # Public API - opaque type
│   │   └── mylib.h       # Main include (includes all)
│   └── internal/
│       └── buffer_internal.h  # Private - only for .c files
├── src/
│   ├── buffer.c          # Implementation
│   ├── list.c            # Implementation
│   └── main.c            # Application
├── tests/
│   └── test_buffer.c
├── Makefile
└── README.md

# 2. Opaque type in action
$ cat include/mylib/buffer.h
// Users can't see inside buffer_t
typedef struct buffer buffer_t;

buffer_t* buffer_create(size_t capacity);
void buffer_destroy(buffer_t* buf);
size_t buffer_write(buffer_t* buf, const void* data, size_t len);
size_t buffer_read(buffer_t* buf, void* dest, size_t len);

$ gcc -c user_code.c -I include
# User cannot access struct internals - only API

# 3. Build system
$ make
Compiling src/buffer.c
Compiling src/list.c
Compiling src/main.c
Linking bin/myapp
Build complete: bin/myapp

$ touch src/buffer.c && make
Compiling src/buffer.c  # Only recompiles changed file
Linking bin/myapp

$ make clean
Removing build artifacts...

$ make test
Running tests...
test_buffer: PASS (10 tests)
test_list: PASS (8 tests)
All tests passed!

Implementation Guide

  1. Reproduce the simplest happy-path scenario.
  2. Build the smallest working version of the core feature.
  3. Add input validation and error handling.
  4. Add instrumentation/logging to confirm behavior.
  5. Refactor into clean modules with tests.

Milestones

  • Milestone 1: Minimal working program that runs end-to-end.
  • Milestone 2: Correct outputs for typical inputs.
  • Milestone 3: Robust handling of edge cases.
  • Milestone 4: Clean structure and documented usage.

Validation Checklist

  • Output matches the real-world outcome example
  • Handles invalid inputs safely
  • Provides clear errors and exit codes
  • Repeatable results across runs

References

  • Main guide: PROFESSIONAL_C_PROGRAMMING_MASTERY.md
  • Effective C, 2nd Edition by Robert C. Seacord