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2kmcc

2k-line mundane C compiler: a self-hosting toy C compiler that's so mundane, your puny C compiler can compile me

(Actually, currently it's closer to 1.5k lines)

作戦部屋

What this is

C compiler self-host struct%

  • compile a subset of C into x64 asm System-V ABI
  • the source code of the compiler must be correctly compilable by the compiler itself
  • the source code of the compiler should be compilable by many other toy C compilers

Assumptions made

The language implemented by this compiler is intended as a subset of C99 - C17. Hence,

  • for(int i = 0; i < 5; i++) { } is supported
  • int foo(); means that it does not make assumptions about the parameter types, while int foo(void); means that there should be no parameters

How to use

Run

make

to build 2kmcc; then run

cat foo.c | xargs -0 -I XX ./2kmcc XX > foo.s
gcc -o foo foo.s -static

to make an executable out of foo.c.

Current status

  • self-hosted in 1500 lines
  • See test_*.py to get an idea on what the compiler can and cannot handle
  • Try make test to see what it can handle; try make embarrass for what it can't
  • Try make test_2ndgen and make test_3rdgen to see that it self-hosts

The following was what I originally planned:

Goal

C compiler self-host struct%

  • compile a subset of C into x64 asm System-V ABI
  • the source code of the compiler must be correctly compilable by the compiler itself
  • the source code of the compiler should be compilable by many other toy C compilers

Rules for the compiler source code

  • Must self-host
  • Must be legible enough
    • codegolf techniques not permitted if it severely hurts legibility
    • it should be such that it is easy to add a new feature
  • Should be short. I ambitiously aim for less than 2k lines

Rules for the language that this compiler accepts

The subset of C that this compiler can compile must be such that it is not painfully unfun to write a realistic program in.

In particular, it must support:

  • multidimensional arrays
  • struct
  • string literals with \n

Why do I aim for 2k lines?

@hiromi-mi's hanando-fukui v1.1.1 is astonishingly short while satisfying the conditions that I put up, with 2203 lines of main.c and 169 lines of main.h. Therefore, I know that this goal is attainable in 2.5k lines; that's why I aim for sub 2k.

Special thanks to

  • Rui Ueyama (@rui314) for writing the compilerbook
  • @spinachpasta for actually typing my experimental design up to step12
  • @hiromi-mi for inspiring me to work on this project