linux下的bison报错，求高手指教！急

[蜗蜗牛快跑]

想用flex+bison写个简单的编译器，生成三地址中间代码。结果bison的编译就一堆警告。。。大概是说定义的文法没有用之类的。

这个是flex文件

%option noyywrap nodefault yylineno

%{
#include "compiler.h"
#include "parsing.tab.h"
%}

%%
"+" |
"-" |
"*" |
"/" |
"=" |
";" |
"(" |
")" |	
"{" |
"}"	{ return yytext[0];}

">"     { yylval.cmp = 1; return CMP; }
"<"     { yylval.cmp = 2; return CMP; }
"!="    { yylval.cmp = 3; return CMP; }
"=="    { yylval.cmp = 4; return CMP; }
">="    { yylval.cmp = 5; return CMP; }
"<="    { yylval.cmp = 6; return CMP; }

"if"    { return IF; }
"else"  { return ELSE; }
"while" { return WHILE; }
"do"    { return DO; }
"break" { return BREAK;}

"&&"	{ return AND;}
"||"	{ return OR;}

"int"	{ yylval.type=1; return TYPE;}
"float"	{ yylval.type=2; return TYPE;}
"bool"	{ yylval.type=3; return TYPE;}

[0-9]+		{ yylval.i=atoi(yytext); return INTEGER;}
[0-9]+"."[0-9]*	{ yylval.d=atof(yytext); return FLOAT;}
"true" |
"false" 	{ yylval.b=strdup(yytext); return BOOLEAN;}

[a-zA-Z][a-zA-Z0-9]*  { yylval.s = lookup(yytext); return ID; }

"//".*
[ \t\n]

.	{ yyerror("error input %c\n",*yytext);}
%%

这个是bison文件，所有的警告都在这里

%{
#include <stdio.h>
#include <stdlib.h>
#include "compiler.h"
%}

%union{
	struct ast *a;

	double d;  
	int i;
	char * b;

	struct symbol *s;

	int cmp;
	int type;
}


%token <i> INTEGER 
%token <d> FLOAT 
%token <b> BOOLEAN
%token <s> ID
%token EOL

%token IF ELSE WHILE DO BREAK
%token AND OR

%token <type> TYPE

%nonassoc <cmp> CMP
%right '='
%left '+' '-'
%left '*' '/'

%type <a> block 
%type <a> decls decl type
%type <a> stmts stmt loc bool 
%type <a> join equality expr term unary factor

%start calclist

%%

block: '{' decls stmts '}'	{ $$=$3;}
;

decls: decls decl	
;
decl: type ID ';'	
;
type: type '[' INTEGER ']'
	| TYPE 		{ $$=newast('X',S1,NULL);}
;

stmts: stmts stmt	{ $$=newast('C',$1,$2);}
;
stmt: loc '=' bool ';'				{ $$=newast('=',$1,$3);}
	| IF '(' bool ')' stmt 			{ $$=newflow('I',$3,$5,NULL);}
	| IF '(' bool ')' stmt ELSE stmt	{ $$=newflow('I',$3,$5,$7);}	
	| WHILE '(' bool ')' stmt		{ $$=newflow('W',$3,$5,NULL);}
	| DO stmt WHILE '(' bool ')' ';'	{ $$=newflow('D',$5,$2,NULL);}
	| BREAK ';'				{ $$=newast('B',NULL,NULL);}
	| block 
;

loc: loc '[' bool ']'		{ $$=newast('[',$1,$3);}
	| ID			{ $$=newref($1);}
;
bool: bool OR join		{ $$=newast('|',$1,$3);}
	| join
;
join: join AND equality		{ $$=newast('&',$1,$3);}
	| equality
;
equality: equality CMP expr	{ $$=newcmp($2,$1,$3);}
	| expr
;
expr: expr '+' term		{ $$=newast('+',$1,$3);}
	| expr '-' term		{ $$=newast('-',$1,$3);}
	| term
;
term: term '*' unary		{ $$=newast('*',$1,$3);}
	| term '/' unary	{ $$=newast('/',$1,$3);}
	| unary
;
unary: '!' unary		{ $$=newast('!',$2,NULL);}
	| '-' unary		{ $$=newast('M',$2,NULL);}
	| factor
;
factor: '(' bool ')' 	{ $$=$2;}
	| loc
	| INTEGER	{ $$=newint($1);}
	| FLOAT		{ $$=newflo($1);}
	| BOOLEAN	{ $$=newbol($1);}
;

calclist:
	| calclist block EOL	{ $2;printf("end\n");}
;
%%

警告大概如下：
parsing.y: 警告: 14 nonterminals useless in grammar
parsing.y: 警告: 36 rules useless in grammar
parsing.y:38.11-15: 警告: nonterminal useless in grammar: block
...(省略)
parsing.y:47.8-41: 警告: rule useless in grammar: block: '{' decls stmts '}'
...(省略)

求高手分析上面定义的文法是否不可以用在bison中，还是我哪里写错了。。。

[蜗蜗牛快跑]

顺便说下，该文法来自于龙书背后的编译器前端。

[赵4老师]

偶遇到类似问题都是用 “每次用/*...*/注释掉不同部分再重新编译，直到定位到具体语法出错的位置。” 的方法解决的。

[那闯]

警告说的很清楚了， block: '{' decls stmts '}' 这个语法没有用到， 没有终结符

[蜗蜗牛快跑]

恩，正在尝试。好像已经找到问题所在了。。。貌似是以下两句导致的 decls: decls decl stmts: stmts stmt { $$=newast('C',$1,$2);} 改为： decls: decls decl | decl stmts: stmts stmt { $$=newast('C',$1,$2);} | stmt 虽然解决了无效文法的问题，但是接着二义性的问题又出现了。。。

[蜗蜗牛快跑]

stmt: loc '=' bool ';'                { $$=newast('=',$1,$3);}
    | IF '(' bool ')' stmt             { $$=newflow('I',$3,$5,NULL);}
    | IF '(' bool ')' stmt ELSE stmt    { $$=newflow('I',$3,$5,$7);}   
    | WHILE '(' bool ')' stmt        { $$=newflow('W',$3,$5,NULL);}
    | DO stmt WHILE '(' bool ')' ';'    { $$=newflow('D',$5,$2,NULL);}
    | BREAK ';'                { $$=newast('B',NULL,NULL);}
    | block 
;

二义性问题出现在if else 和while 模块。。。有这方面解决经验的高手，不吝赐教呀～～～

[蜗蜗牛快跑]

 状态 63

    8 stmt: IF '(' bool ')' stmt .
    9     | IF '(' bool ')' stmt . ELSE stmt

    ELSE  shift, and go to state 72

    ELSE      [reduce using rule 8 (stmt)]
    $default  reduce using rule 8 (stmt)

不好意思，说错了，二义性仅存在于if else模块