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TinyC-like Compiler

Posted on Edited on In Disqus:
Implementation of a tinyc-like compiler. About Tiny C Compiler : The Tiny C Compiler (a.k.a. TCC, tCc, or TinyCC) is an x86, X86-64 and ARM processor C compiler initially written by Fabrice Bellard. It is designed to work for slow computers with little disk space (e.g. on rescue disks). Windows operating system support was added in version 0.9.23 (17 Jun 2005). TCC is distributed under the GNU Lesser General Public License.

Overview

  • tinyc basics
  • frontend
  • backend

TinyC basics

tokens in tinyC

According to their lexical characteristics, the tokens in tinyC are divided into the following three categories.

  1. single char operator ( 15 kinds )

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    + * - / % = , ; ! < > ( ) { }

  2. double char operator ( 6 kinds ) and keywords ( 10 kinds )

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    <= >= == != && ||
    void int while if else return break continue print readint

  3. integer constant, string constant, identifier ( variable name and function name ), ( 3 kinds )

numbering principle

  • single char op : the token number is the value of its character.
  • others : the token number are numbered from 256

notes

  • When you are writing the rule for single char op, please pay attention to the character ‘-‘ in RegExp :

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    (wrong) : {OPERATOR} {[+-*/%=,;<>(){}]} 
    (right) : {OPERATOR} {[+\-*/%=,;<>(){}]} <-- 正则表达式'-'需要转义字符

Frontend

Grammar on tools

flex

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%{
Declarations
%}
Definitions
%%
Rules
%%
User subroutines

bison

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%{
Declarations
%}
Definitions
%%
Productions
%%
User subroutines

Details

scanner.l

  1. When I’m implementing scanner.l, I find that different order can lead to different results or even errors! For example, first order is like:

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    "int"           { return T_Int; }
    "print"         { return T_Print; }
    ...
    {IDENTIFIER}    { _DUPTEXT; return T_Identifier;        }

    second order is like:

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    {IDENTIFIER}    { _DUPTEXT; return T_Identifier;        }
    ...
    "int"           { return T_Int; }
    "print"         { return T_Print; }

    the second one results in an error! Because compiler doesn’t know int is a keyword, instead, it treats int as an identifier! Therefore, you need to put all keyword rules before the identifier!!!

Backend

NASM

  • The Netwide Assembler based on x86

Reference