README.md

SOCC - Simple C Compiler in OCaml

SOCC is a simple C Compiler written in OCaml using ocamllex and menhir.

Install

Dependences: core, ppx_jane

opam update
opam install core ppx_jane

git clone [email protected]:noti0na1/socc.git
cd socc
make

The executable file is main.native

Usage

# use gcc to preprocess the source code
gcc -E test.c -o test.e.c
./main.native < test.e.c > test.s
gcc test.s -o test
./test

Example

There are 4 buildin functions for test:

• void println(int)
• int readi()
• void *malloc(size_t)
• void free(void *)

int main() {
    int *pi = malloc(sizeof(int));
    int max = readi();
    for (int i = 0; i < max; i += 2) {
        println(i);
        *pi += i;
    }
    println(*pi);
    free(pi);
    return 0;
}

.LC0:
	.string "%d\n"
	.globl println
println:
	movq	%rdi, %rsi
	movq	$0, %rax
	movl	$.LC0, %edi
	jmp	printf
.LC1:
	.string "%d"
	.globl readi
readi:
	subq	$24, %rsp
	movl	$.LC1, %edi
	movq	$0, %rax
	leaq	12(%rsp), %rsi
	movl	$0, 12(%rsp)
	call	__isoc99_scanf
	movl	12(%rsp), %eax
	addq	$24, %rsp
	ret
	.globl main
main:
	pushq	%rbp
	movq	%rsp, %rbp
	movq	$4, %rax
	movq	%rax, %rdi
	call	malloc
	pushq	%rax
	call	readi
	pushq	%rax
	movl	$0, %eax
	pushq	%rax
LmainFORA0:
	movq	-24(%rbp), %rax
	pushq	%rax
	movq	-16(%rbp), %rax
	movq	%rax, %rcx
	popq	%rax
	cmpl	%ecx, %eax
	movl	$0, %eax
	setl	%al
	cmpl	$0, %eax
	je	LmainFORC0
	movq	-24(%rbp), %rax
	movq	%rax, %rdi
	call	println
	movq	-8(%rbp), %rax
	pushq	%rax
	movq	-8(%rbp), %rax
	movq	(%rax), %rax
	pushq	%rax
	movq	-24(%rbp), %rax
	movq	%rax, %rcx
	popq	%rax
	addl	%ecx, %eax
	movq	%rax, %rcx
	popq	%rax
	movl	%ecx, (%rax)
	addq	$0, %rsp
LmainFORB0:
	movq	-24(%rbp), %rax
	pushq	%rax
	movl	$2, %eax
	movq	%rax, %rcx
	popq	%rax
	addl	%ecx, %eax
	movq	%rax, -24(%rbp)
	jmp	LmainFORA0
LmainFORC0:
	addq	$8, %rsp
	movq	-8(%rbp), %rax
	movq	(%rax), %rax
	movq	%rax, %rdi
	call	println
	movq	-8(%rbp), %rax
	movq	%rax, %rdi
	call	free
	movl	$0, %eax
	leave
	ret

In: 23

Out:

0
2
4
6
8
10
12
14
16
18
20
22
132

Structure

• socc/src source code
  • ast.ml abstract syntax tree
  • parser.mly parser
  • lexer.mll lexer
  • context.ml
  • x64.ml X64 assembly
  • templib.ml temporery lib (println, readi)
  • generate.ml code generator
  • util.ml utils
  • main.ml program entry
• socc/test some test files

Note

Core is used across the project

The output assembly is for x64 Linux platform

TODO

Short Term

• follow the C11 to edit lexer
• add array type and array operate
• implement ++ and --
• support comments
• add more type, implement struct, union, enum
• complete type system
• optimize stack usage
• improve parser further more

Long Term

• add error, warning print ...
• add semantic check pass
• add intermediate lang

References

Writing a C Compiler

nlsandler/nqcc

Parsing with OCamllex and Menhir

Lexer and parser generators (ocamllex, ocamlyacc)

x64_cheatsheet

Licence

SOCC is distributed under the terms of MIT License

Copyright (c) 2018 noti0na1