Project 1: Memory Arena Allocator

A custom arena allocator from scratch that implements Odin’s allocator interface, with support for reset, free_all, and memory tracking.

Quick Reference

Attribute	Value
Primary Language	Odin
Alternative Languages	C, Rust, Zig
Difficulty	Level 2: Intermediate
Time Estimate	Weekend
Knowledge Area	Memory Management / Allocators
Tooling	Custom implementation
Prerequisites	Basic programming concepts, understanding of pointers

What You Will Build

A custom arena allocator from scratch that implements Odin’s allocator interface, with support for reset, free_all, and memory tracking.

Why It Matters

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

Core Challenges

Implementing the Allocator interface → maps to understanding Odin’s memory model
Managing a contiguous memory block → maps to low-level memory layout
Supporting alignment requirements → maps to CPU cache optimization
Integrating with the context system → maps to Odin’s implicit context

Key Concepts

Allocator Interface: Odin Overview - Allocators
Arena Allocators: “Understanding the Odin Programming Language” Ch. 8
Context System: Karl Zylinski - Temporary Allocator
Memory Alignment: “Computer Systems: A Programmer’s Perspective” Ch. 3

Real-World Outcome

$ odin run arena_demo

Arena Allocator Demo
--------------------
Created arena with 1MB capacity

Allocating 1000 structs...
  Allocated: 1000 × Entity (48 bytes each)
  Total used: 48,000 bytes
  Alignment: 8-byte aligned ✓

Allocating strings...
  "Hello, Odin!" at 0x7f8b4c048000
  "Arena allocators are fast!" at 0x7f8b4c04800d

Reset arena (instant free)...
  Used: 0 bytes
  Capacity: 1,048,576 bytes

Stress test: 100,000 allocations...
  Arena time:  0.8ms
  Heap time:   45.2ms
  Speedup:     56x faster!

Implementation Guide

Reproduce the simplest happy-path scenario.
Build the smallest working version of the core feature.
Add input validation and error handling.
Add instrumentation/logging to confirm behavior.
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: LEARN_ODIN_PROGRAMMING_LANGUAGE.md
“Understanding the Odin Programming Language” by Karl Zylinski