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https://github.com/tamaroning/ccr

a toy C Compiler written in Rust [old]
https://github.com/tamaroning/ccr

Last synced: 19 days ago
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a toy C Compiler written in Rust [old]

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# ccr

Ccr is a toy C compiler written in Rust language, which I am making in order to understand compilers and Rust.  

This software supports a small subset of C and outputs x64 GNU assembler.  

Ccr is not so fast, but the source code is easy for beginners to read.   

My new C compiler is available [here](https://github.com/tamaroning/ironcc).



# Usage

## Build ccr

To use ccr, run the following scripts:



```sh

$ git clone https://github.com/tamaroning/ccr

$ cd ccr

$ cargo build

```



## Run

After the build, Compile text(.c) file:  



```sh

$ ./target/debug/ccr [file path]

```

By default, the assembly is written to ```debug/target/tmp.s```.  

  

Then assemble ```debug/taeget/tmp.s``` into an executable binary:  



```sh

$ cc debug/target/tmp.s

$ ./a.out

```



After execute the binary, to check the return value, run:  



```sh

$ echo $?

```

Make sure that the return value is cure in the range of 0~255.  



## Test

To execute the demo, run:  



```sh

$ ./test/test-all.sh

```



# Implemented features

- Numeric literals (only signed integer) (ex: 0, 24, +4, -699)

- Basic arithmetic operators (+, -, *, /)

- Dereference and address operators (*, &)

- Comparison operators (==, !=, >, <=/>=)

- Local variables (need to be declared)

- Variable declaration and initialization (ex: int a, b = 0;)

- Return statement

- Assignment (ex: a = 4*3;)

- Control syntax (if-else, for, while)



## Example 1

Ccr can compile programs like the following: 



```c

int main(void) {

    int sum = 0;

    int width = 3;

    for ( i = 1; i <= width; i = i + 1) {

        for (j = 1; j <= width; j = j + 1) {

            sum = sum + 1;

        }

    }



    if (sum == 9) return 1;

    else return 0;

}

```



## Example 2

You can use functions which is defined in other object files:  

```c

int main(void) {

    int i;

    for(i = 0; i < 10; i = i + 1) {

        foo();

    }

    return 0;

}

```

In this case, foo() is defined in an .o file.

And you need to link the .o file to the assembly dumped by ccr.  



# Todo

## Steps  

- [x] 簡単な式(例: 3+12-5)の結果を出力する

- [x] EBNFによる文法の定義と再帰下降構文解析

- [x] スタックマシンへのコンパイル

- [x] 単項プラス/マイナス

- [x] 比較演算子

- [x] ローカル変数

- [x] return文

- [x] if-else, for, while

- [x] {}ブロック

- [x] 関数呼び出し

- [x] 単項*と& (derefとaddr)

- [x] 型 (int, int*, int**, ...)

- [x] 変数の定義,宣言

- [x] 関数定義



##  Refactoring and improvement

- [x] .cファイルを読み込んで.sファイルを吐き出せるようにする

- [x] 標準出力に実行中の情報を出力できるようにする

- [ ] コード生成時に検出されるエラー出力の強化

- [ ] 戻り値のチェック



## Issues

- [x] for(;;){}を受け付けるようにexpr=Nilを許容する

    - 後ろに;が続く場合のみ許容

- [ ] for(int i = 0;;)のようにfor内で変数の定義ができるようにする

- [ ] 全ての型が8byteになってしまっている

- [ ] 関数呼び出し時のスタックフレームの確保(スタックフレームサイズの把握)とretの数を修正する

- [ ] 6つ以上の引数の関数呼び出し

- [ ] EBNFの修正 C言語の正しい文法にする

- [ ] 変数スコープの実装

{}ブロックによってスコープが形成される。例えば、



```c

int main(void) {

    int a= 1;

    {

        int a = 2;

        int b = 3;

    }

    return b; // Error

}

```



# Internals

Ccr is designed with reference to chibicc.  

If you want to laern the internals, please read [chibicc internals](https://github.com/rui314/chibicc#internals)  



# References

0. [低レイヤを知りたい人のためのCコンパイラ作成入門](https://www.sigbus.info/compilerbook#), Rui Ueyama

1. [chibicc: A Small C Compiler](https://github.com/rui314/chibicc), rui314

2. [Compilers: Principles, Techniques, and Tools](https://www.amazon.com/Compilers-Principles-Techniques-Tools-2nd/dp/0321486811), Alfred V.Aho, Monica S.Lam, Ravi Sethi, and Jeffrey D.Ullman

3. [A Grammar for the C- Programming Language](http://marvin.cs.uidaho.edu/Teaching/CS445/c-Grammar.pdf), Robert Heckendorn