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Some time ago I decided I wanted to create a c compiler for the Hack processor in the nand2tetris book. After several dead end attempts that I might describe later I found this book : Writing a C Compiler | No Starch Press
I decided to work my way through it. I plan to do blog posts as I progress through it, probably chapter by chapter.
I have emailed the author a couple of times and have got helpful timely replies! – thank you
What makes the book so good?
Step by step
By the end of chapter 1 you have a working compiler. Each subsequent chapter adds more features. The chapter 1 compiler can only handle
int main(void){ return <constant>; }But it works producing a complete executable
Chapter 2 adds unary operators so we can now do something like.
int main(void){ return ~3; }This contrasts with most other books I have worked with on compilers like the also excellent Crafting Interpreters and Home | nand2tetris
The fact that we are building a real language as opposed to a made up one is great too.
Side note: Some c features are not implemented in the book but are suggested as ‘extra credit’. I intend to implement all those. Some features are not implemented and are not covered. More on those later.
Test suite
The other great thing is that there is a large test suite provided. For each chapter tests are added so running the , say, chapter 5 tests runs the tests for 1,2,3 and 4 as well.
You can say if you want to test:
- extra credit features
- just the lexer pass
- the lex and parser pass
- semantic analysis
- everything
Even the simple compiler in chapter 1 has 24 tests
This is a tremendous resource and seeing the test suite say
PS C:\work\forks\writing-a-c-compiler-tests> python .\test_compiler C:\work\mycc\target\debug\mycc.exe --chapter 1 --extra-credit ---------------------------------------------------------------------- Ran 24 tests in 2.843s OKis a real pleasure. Time to fire up gitui (gitui-org/gitui: Blazing 💥 fast terminal-ui for git written in rust 🦀) and commit
Repos
Nora has two github repos for this book
- nlsandler/writing-a-c-compiler-tests: Test cases for Writing a C Compiler this is the test suite
- nlsandler/nqcc2: Reference implementation for Writing a C Compiler this is an ocaml implementation of the compiler. It does not implement the extra credit features
I have two as well
- pm100/writing-a-c-compiler-tests: Test cases for Writing a C Compiler a fork of the original with a few changes and bug fixes. Mainly to do with Windows support (see later post)
- pm100/mycc my implementation in rust. Like the nqcc2 repo it has (mainly) a commit per chapter
Posts
I will probably do one blog post per chapter, including one for the introduction. I got to the extra credit section of chapter 8 before I thought of blogging the process. So there will be a bunch of posts in a rush, that cover completed work and will be in the past tense. As I move forward, they will be chattier as I debate with myself how to do things, and spread out to the pace of my progress
Final Note
This is a great book. Any comments I make in later chapter regarding things that I think are missing, wrong, confusing etc. should not take away from the fact that this is an extremely good book.
