lcc 源代码解析之token.h

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元旦憋了两天，终究是没能透彻的理解表达式的语法分析，关于这部分等我自己搞明白再分享出来，

又要开工了，每天只有有限的时间区分析代码，再加上还要抽空看看面试题，估计要费一段时间了。

先分享一道小菜，即头文件token.h，这是一个十分重要的头文件，用的也很奇妙，当然，这损失了代码的部分可读性。

/* $Id: token.h,v 1.1 2002/08/28 23:12:47 drh Exp $ *//*xx(symbol,value,prec,op,optree,kind,string)(枚举标示符,  字符值,  单词操作符的优先顺序,  通用操作符,  创建树的函数,  单词集合,  字符串表示)yy处理单字符单词，xx处理多字符单词和其他*/yy(0,         0,     0,      0,    0,      0,      0)xx(FLOAT,     1,     0,      0,    0,      CHAR,   "float")xx(DOUBLE,    2,     0,      0,    0,      CHAR,   "double")xx(CHAR,      3,     0,      0,    0,      CHAR,   "char")xx(SHORT,     4,     0,      0,    0,      CHAR,   "short")xx(INT,       5,     0,      0,    0,      CHAR,   "int")xx(UNSIGNED,  6,     0,      0,    0,      CHAR,   "unsigned")xx(POINTER,   7,     0,      0,    0,      0,      "pointer")xx(VOID,      8,     0,      0,    0,      CHAR,   "void")xx(STRUCT,    9,     0,      0,    0,      CHAR,   "struct")xx(UNION,    10,     0,      0,    0,      CHAR,   "union")xx(FUNCTION, 11,     0,      0,    0,      0,      "function")xx(ARRAY,    12,     0,      0,    0,      0,      "array")xx(ENUM,     13,     0,      0,    0,      CHAR,   "enum")xx(LONG,     14,     0,      0,    0,      CHAR,   "long")xx(CONST,    15,     0,      0,    0,      CHAR,   "const")xx(VOLATILE, 16,     0,      0,    0,      CHAR,   "volatile")yy(0,        17,     0,      0,    0,      0,      0)yy(0,        18,     0,      0,    0,      0,      0)yy(0,        19,     0,      0,    0,      0,      0)yy(0,        20,     0,      0,    0,      0,      0)yy(0,        21,     0,      0,    0,      0,      0)yy(0,        22,     0,      0,    0,      0,      0)yy(0,        23,     0,      0,    0,      0,      0)yy(0,        24,     0,      0,    0,      0,      0)yy(0,        25,     0,      0,    0,      0,      0)yy(0,        26,     0,      0,    0,      0,      0)yy(0,        27,     0,      0,    0,      0,      0)yy(0,        28,     0,      0,    0,      0,      "long long")yy(0,        29,     0,      0,    0,      0,      0)yy(0,        30,     0,      0,    0,      0,      0)yy(0,        31,     0,      0,    0,      0,      "const volatile")xx(ID,       32,     0,      0,    0,      ID,     "identifier")yy(0,        33,     0,      0,    0,      ID,     "!")xx(FCON,     34,     0,      0,    0,      ID,     "floating constant")xx(ICON,     35,     0,      0,    0,      ID,     "integer constant")xx(SCON,     36,     0,      0,    0,      ID,     "string constant")yy(0,        37,     13,     MOD,  bittree,'%',    "%")yy(0,        38,     8,      BAND, bittree,ID,     "&")xx(INCR,     39,     0,      ADD,  addtree,ID,     "++")yy(0,        40,     0,      0,    0,      ID,     "(")yy(0,        41,     0,      0,    0,      ')',    ")")yy(0,        42,     13,     MUL,  multree,ID,     "*")yy(0,        43,     12,     ADD,  addtree,ID,     "+")yy(0,        44,     1,      0,    0,      ',',    ",")yy(0,        45,     12,     SUB,  subtree,ID,     "-")yy(0,        46,     0,      0,    0,      '.',    ".")yy(0,        47,     13,     DIV,  multree,'/',    "/")xx(DECR,     48,     0,      SUB,  subtree,ID,     "--")xx(DEREF,    49,     0,      0,    0,      DEREF,  "->")xx(ANDAND,   50,     5,      AND,  andtree,ANDAND, "&&")xx(OROR,     51,     4,      OR,   andtree,OROR,   "||")xx(LEQ,      52,     10,     LE,   cmptree,LEQ,    "<=")xx(EQL,         53,     9,      EQ,     eqtree, EQL,    "==")xx(NEQ,         54,     9,      NE,     eqtree, NEQ,    "!=")xx(GEQ,         55,     10,     GE,     cmptree,GEQ,    ">=")xx(RSHIFT,      56,     11,     RSH,    shtree, RSHIFT, ">>")xx(LSHIFT,      57,     11,     LSH,    shtree, LSHIFT, "<<")yy(0,           58,     0,      0,      0,      ':',    ":")yy(0,           59,     0,      0,      0,      IF,     ";")yy(0,           60,     10,     LT,     cmptree,'<',    "<")yy(0,           61,     2,      ASGN,   asgntree,'=',   "=")yy(0,           62,     10,     GT,     cmptree,'>',    ">")yy(0,           63,     0,      0,      0,      '?',    "?")xx(ELLIPSIS,    64,     0,      0,      0,      ELLIPSIS,"...")xx(SIZEOF,      65,     0,      0,      0,      ID,     "sizeof")yy(0,           66,     0,      0,      0,      0,      0)xx(AUTO,        67,     0,      0,      0,      STATIC, "auto")xx(BREAK,       68,     0,      0,      0,      IF,     "break")xx(CASE,        69,     0,      0,      0,      IF,     "case")xx(CONTINUE,    70,     0,      0,      0,      IF,     "continue")xx(DEFAULT,     71,     0,      0,      0,      IF,     "default")xx(DO,          72,     0,      0,      0,      IF,     "do")xx(ELSE,        73,     0,      0,      0,      IF,     "else")xx(EXTERN,      74,     0,      0,      0,      STATIC, "extern")xx(FOR,         75,     0,      0,      0,      IF,     "for")xx(GOTO,        76,     0,      0,      0,      IF,     "goto")xx(IF,          77,     0,      0,      0,      IF,     "if")xx(REGISTER,    78,     0,      0,      0,      STATIC, "register")xx(RETURN,      79,     0,      0,      0,      IF,     "return")xx(SIGNED,      80,     0,      0,      0,      CHAR,   "signed")xx(STATIC,      81,     0,      0,      0,      STATIC, "static")xx(SWITCH,      82,     0,      0,      0,      IF,     "switch")xx(TYPEDEF,     83,     0,      0,      0,      STATIC, "typedef")xx(WHILE,       84,     0,      0,      0,      IF,     "while")xx(TYPECODE,    85,     0,      0,      0,      ID,     "__typecode")xx(FIRSTARG,    86,     0,      0,      0,      ID,     "__firstarg")yy(0,           87,     0,      0,      0,      0,      0)yy(0,           88,     0,      0,      0,      0,      0)yy(0,           89,     0,      0,      0,      0,      0)yy(0,           90,     0,      0,      0,      0,      0)yy(0,           91,     0,      0,      0,      '[',    "[")yy(0,           92,     0,      0,      0,      0,      0)yy(0,           93,     0,      0,      0,      ']',    "]")yy(0,           94,     7,      BXOR,   bittree,'^',    "^")yy(0,           95,     0,      0,      0,      0,      0)yy(0,           96,     0,      0,      0,      0,      0)yy(0,           97,     0,      0,      0,      0,      0)yy(0,           98,     0,      0,      0,      0,      0)yy(0,           99,     0,      0,      0,      0,      0)yy(0,           100,    0,      0,      0,      0,      0)yy(0,           101,    0,      0,      0,      0,      0)yy(0,           102,    0,      0,      0,      0,      0)yy(0,           103,    0,      0,      0,      0,      0)yy(0,           104,    0,      0,      0,      0,      0)yy(0,           105,    0,      0,      0,      0,      0)yy(0,           106,    0,      0,      0,      0,      0)yy(0,           107,    0,      0,      0,      0,      0)yy(0,           108,    0,      0,      0,      0,      0)yy(0,           109,    0,      0,      0,      0,      0)yy(0,           110,    0,      0,      0,      0,      0)yy(0,           111,    0,      0,      0,      0,      0)yy(0,           112,    0,      0,      0,      0,      0)yy(0,           113,    0,      0,      0,      0,      0)yy(0,           114,    0,      0,      0,      0,      0)yy(0,           115,    0,      0,      0,      0,      0)yy(0,           116,    0,      0,      0,      0,      0)yy(0,           117,    0,      0,      0,      0,      0)yy(0,           118,    0,      0,      0,      0,      0)yy(0,           119,    0,      0,      0,      0,      0)yy(0,           120,    0,      0,      0,      0,      0)yy(0,           121,    0,      0,      0,      0,      0)yy(0,           122,    0,      0,      0,      0,      0)yy(0,           123,    0,      0,      0,      IF,     "{")yy(0,           124,    6,      BOR,    bittree,'|',    "|")yy(0,           125,    0,      0,      0,      '}',    "}")yy(0,           126,    0,      BCOM,   0,      ID,     "~")xx(EOI,         127,    0,      0,      0,      EOI,    "end of input")#undef xx#undef yy

从上面的头文件中可以看出，这是个类似表的结构，按照列的不同处理不同的部分，

下面来看一下使用的部分，这六个数据结构需要比较熟悉，不然会对代码的理解产生干扰

//使用地：c.h//作用：声明操作符枚举,使用了表的第一二两列enum {#define xx(a,b,c,d,e,f,g) a=b,#define yy(a,b,c,d,e,f,g)#include "token.h"}//预处理之后就变成了下面的样子，//建议将这个表处理成以下这个形式，便于代码阅读enum {FLOAT = 1,   DOUBLE = 2,CHAR = 3,SHORT = 4,INT = 5,UNSIGNED = 6,POINTER = 7,VOID = 8,STRUCT = 9,UNION = 10,  FUNCTION = 11,  ARRAY = 12, ENUM = 13,  LONG = 14, CONST = 15, VOLATILE = 16, ID = 32,FCON = 34,ICON = 35, SCON = 36,INCR = 39,DECR = 48,DEREF = 49,ANDAND = 50,OROR = 51,LEQ = 52,EQL = 53,NEQ = 54,GEQ = 55,RSHIFT = 56,LSHIFT = 57,ELLIPSIS = 64,SIZEOF = 65,AUTO = 67,BREAK = 68,CASE = 69,CONTINUE = 70,DEFAULT = 71,DO = 72,ELSE = 73,EXTERN = 74,FOR = 75,GOTO = 76,IF = 77,REGISTER = 78,RETURN = 79,SIGNED = 80,STATIC = 81,SWITCH = 82,TYPEDEF = 83,WHILE = 84,TYPECODE = 85,FIRSTARG = 86,EOI = 127,LAST};//使用地：enode.c//作用：创建“创建树的函数指针的数组”，即表中的倒数第三列Tree (*optree[])(int, Tree, Tree) = {#define xx(a,b,c,d,e,f,g) e,#define yy(a,b,c,d,e,f,g) e,#include "token.h"};//使用地：error.c//作用：创建单词集合数组，倒数第二列char kind[] = {#define xx(a,b,c,d,e,f,g) f,#define yy(a,b,c,d,e,f,g) f,#include "token.h"};//使用地：expr.c//作用：创建操作符的优先级数组static char prec[] = {#define xx(a,b,c,d,e,f,g) c,#define yy(a,b,c,d,e,f,g) c,#include "token.h"};//作用：创建通用操作符数组static int oper[] = {#define xx(a,b,c,d,e,f,g) d,#define yy(a,b,c,d,e,f,g) d,#include "token.h"};//使用地：output.c//作用：创建词素的字符串数组static char *tokens[] = {#define xx(a,b,c,d,e,f,g) g,#define yy(a,b,c,d,e,f,g) g,#include "token.h"};

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