TinyGC.NET - Educational Garbage Collector

A simple, educational garbage collector written in C# for .NET. Perfect for students learning how garbage collection works!

What is Garbage Collection?

Garbage Collection (GC) is automatic memory management. When you create objects in code, they're stored in memory. When you're done with them, the GC automatically frees that memory so other programs can use it.

How to Run

dotnet run

How It Works

Our GC uses Mark-Sweep algorithm with 3 phases:

1. MARK PHASE

• Start from "roots" (variables in your code)
• Mark every object we can reach as alive

2. SWEEP PHASE

• Walk through all objects in the heap
• If object is NOT marked → it's garbage! Free it.
• If object IS marked → keep it

3. COMPACT PHASE

• Move objects together to reduce gaps (simplified in this version)

Project Structure

File	Purpose
GCObject.cs	Base class for all GC objects
Heap.cs	Memory manager
GC.cs	Main GC with Mark/Sweep
GcRootHandle.cs	Keeps objects alive
MyData.cs	Example test class
Program.cs	Demo program

Example Usage

// Allocate an object
var obj = GC.Instance.New<MyData>();
obj.Value = 42;
obj.Name = "Test";

// Run garbage collection
GC.Instance.Collect();

// Print statistics
GC.Instance.PrintStats();

Key Concepts Learned

1. Bump Pointer Allocation - Fast memory allocation (just increment an index)
2. Free List - Track freed memory for reuse
3. Mark-Sweep - Foundation of GC algorithms
4. Root Handles - References that keep objects alive
5. Object Headers - Metadata about each object

For Students

Try these exercises:

1. Add reference tracing - follow references within objects
2. Implement compaction - move objects together
3. Add generational GC - young/old generations
4. Use Marshal.AllocHGlobal - real OS memory

References

• Writing a .NET GC in C# - Kevin Gosse
• Mark-Sweep GC Tutorial

License

GNU General Public License v3.0 - See LICENSE file

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Happy Learning! 🚀