Chapter 27: Self-Hosting

**NanoLang compiler written in NanoLang.**

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NanoLang is self-hosting: the compiler is written in NanoLang itself and compiles to C.

24.1 Dual Implementation

**ALL language features require 2× implementation:**

  • C reference compiler: src/*.c
  • NanoLang self-hosted: src_nano/*.nano

This constraint drives language design:

  • ✅ Simple, regular grammar
  • ✅ Explicit over implicit
  • ❌ Avoid complex features requiring parser changes

24.2 Compiler Pipeline


NanoLang source (.nano)
    ↓ lexer.nano
Tokens
    ↓ parser.nano
AST
    ↓ typecheck.nano
Typed AST
    ↓ transpiler.nano
C code (.c)
    ↓ gcc/clang
Native binary

24.3 Bootstrap Process

1. **Stage 0:** C compiler compiles itself

2. **Stage 1:** C compiler compiles NanoLang compiler

3. **Stage 2:** NanoLang compiler compiles itself

4. **Stage 3:** Verify stage 2 and stage 3 are identical

24.4 Compiler Modules

  • src_nano/compiler/lexer.nano - Tokenization
  • src_nano/compiler/parser.nano - AST construction
  • src_nano/compiler/typecheck.nano - Type checking
  • src_nano/compiler/transpiler.nano - C code generation

Summary

Self-hosting benefits:

  • ✅ "Dog-fooding" the language
  • ✅ Ensures language is practical
  • ✅ Tests every feature
  • ✅ Drives simplicity

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**Previous:** Chapter 26: LLM Code Generation

**Next:** Chapter 25: Contributing

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