LCC编译器的源程序分析(64)符号表的结构注释

符号表是用来保存每个符号信息的，因为编译器分析源程序的过程会生成很多符号的属性，后端根据这些属性来生成合适的指令和代码的格式。 #001 //符号表结构.#002 //#003 //蔡军生 2007/08/10 QQ:9073204#004 //#005 struct symbol #006 {#007  char *name; //符号的名称,大多数情况是源程序的符号.#008  int scope; //符号作用域.#009  Coordinate src; //符号出现在文件中的行号和列号.#010  Symbol up; //#011  List uses;#012  int sclass; //符号的类型.#013  unsigned structarg:1; //结构参数标志.#014 #015  unsigned addressed:1; //地址访问的变量.#016  unsigned computed:1; //地址树的标志.addrtree函数处理.#017  unsigned temporary:1; //生成的临时变量标志.#018  unsigned generated:1; //生成的符号标志.#019  unsigned defined:1; //符号被定义了,避免声明多次.#020  Type type; //变量或者常量的类型.#021  float ref; //标号或变量的引用计数.#022  union #023  {#024         //保存标号.#025          struct #026         {               #027               int label; //全局分配唯一的标号,这时name保存标号字符串.#028               Symbol equatedto;#029         } l;#030 #031         struct #032         {#033               unsigned cfields:1;#034               unsigned vfields:1;#035               Table ftab;       /* omit */#036               Field flist;#037         } s;#038 #039         int value;#040         Symbol *idlist;#041 #042         struct #043         {#044               Value min, max;#045         } limits;#046 #047         //保存常量的结构.#048         struct #049         {#050               Value v; //保存实际的常量值.#051               Symbol loc; //指向符号表的入口.#052         } c;#053         #054         struct #055         {#056               Coordinate pt;#057               int label;#058               int ncalls;#059               Symbol *callee;#060         } f;#061         #062         //全局变量或静态变量给出定义的段.#063         int seg;#064 #065         Symbol alias;#066         #067         struct #068         {#069               //前端生成多次引用公共表达式的临时变量的DAG节点.#070               Node cse;#071 #072               //#073               int replace;#074               Symbol next;#075         } t;#076 #077  } u;#078 #079  Xsymbol x; //后端使用的符号扩展。#080 };