How to write a compiler from scratch in 30 minutes

This repository explains how to write a compiler from scratch by Go.

The compiler has some constraints

Can compile only arithmetic operations.
Runs only on Linux
Outputs X86-64 assembly (GAS)

Usage

First you need to run a docker container and get in it.

./docker-run

And then you can use the compiler.

$ echo '30 + 12' | go run main.go

This program receives source code from stdin, and emits assembly code to stdout.

If you want to compile and run at once, asrun script helps you.

$ echo '30 + 12' | go run main.go | ./asrun

asrun takes assembly code from stdin and executes it while displaying the code and the resulting status code.

$ echo  '30 + 12' | go run main.go | ./asrun
-------- a.s ----------------
  .global main
main:
  movq  $30, %rax
  movq  $12, %rcx
  addq %rcx, %rax
  ret
-------- result -------------
42

Design

The compiler has 3 phases.

Source Code -> [Tokenizer] -> Tokens -> [Parser] -> AST -> [Code Generator] -> Assembly

Tokenizer

Source Code -> [Tokenizer] -> Tokens

Tokenizer analyzes the byte stream of source code, and breaks it down into a list of tokens.

In this compiler, the function tokenize() does this task.

Parser

Tokens -> [Parser] -> AST

Parser analyzes stream of tokens, and composes a tree of nested structs , which represents sytanx structure of source code.

This tree is called AST (Abstract Syntax Tree).

The function parser() does this task.

Code Generator

AST -> [Code Generator] -> Assembly

Code generator converts AST into target language code.

In this compiler, the target language is GAS(GNU Assembly) for X86-64 linux.

The function generateCode() does this task.

How to run unit tests

$ ./test.sh

SEE ALSO

This project is based on the history of my Go compiler.

https://github.com/DQNEO/minigo

Actually, the first 7 commits of minigo are equivalent to the whole history of this repo.

License

MIT License

Author

@DQNEO

License

DQNEO/HowToWriteACompiler

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