Question

我是flex和Bison的新手。以下bison文件无法编译生成.cpp和.h文件：

如果我删除代码以支持if语句，那么它可以工作。 |ifStmt{$$=$1;}中的statement:，规则ifStmt: TOKEN_IF expression TOKEN_DO statement TOKEN_ELSE TOKEN_DO statement{$$=makeIf($2, $3, $7);};并通过删除TOKEN_IF和TOKEN_ELSE来更改令牌声明

%error-verbose /* instruct bison to generate verbose error messages*/
%{
#include "astgen.h"
#define YYDEBUG 1

/* Since the parser must return the AST, it must get a parameter where
 * the AST can be stored. The type of the parameter will be void*. */
struct AstElement* astDest;
extern int yylex();
%}

%union {
    int val;
    char op;
    char* name;
    struct AstElement* ast; /* this is the new member to store AST elements */
}

%token TOKEN_BEGIN TOKEN_END TOKEN_WHILE TOKEN_DO TOKEN_IF TOKEN_ELSE
%token<name> TOKEN_ID
%token<val> TOKEN_NUMBER
%token<op> TOKEN_OPERATOR
%type<ast> program block statements statement assignment expression whileStmt call
%start program

%{
/* Forward declarations */
void yyerror(const char* const message);


%}

%%

program: statement';' { astDest = $1; };

block: TOKEN_BEGIN statements TOKEN_END{ $$ = $2; };

statements: {$$=0;}
    | statements statement ';' {$$=makeStatement($1, $2);}
    | statements block';' {$$=makeStatement($1, $2);};

statement: 
      assignment {$$=$1;}
    | whileStmt {$$=$1;}
    | ifStmt{$$=$1;}
    | block {$$=$1;}
    | call {$$=$1;}

assignment: TOKEN_ID '=' expression {$$=makeAssignment($1, $3);}

expression: TOKEN_ID {$$=makeExpByName($1);}
    | TOKEN_NUMBER {$$=makeExpByNum($1);}
    | expression TOKEN_OPERATOR expression {$$=makeExp($1, $3, $2);}

whileStmt: TOKEN_WHILE expression TOKEN_DO statement{$$=makeWhile($2, $4);};

ifStmt: TOKEN_IF expression TOKEN_DO statement TOKEN_ELSE TOKEN_DO statement{$$=makeIf($2, $4, $7);};

call: TOKEN_ID '(' expression ')' {$$=makeCall($1, $3);};

%%

#include "astexec.h"
#include <stdlib.h>

void yyerror(const char* const message)
{
    fprintf(stderr, "Parse error:%s\n", message);
    exit(1);
}

上面的lex文件是：

%option noyywrap

%{
#include "parser.tab.h"
#include <stdlib.h>
%}

%option noyywrap

%%

"while" return TOKEN_WHILE;
"{" return TOKEN_BEGIN;
"}"   return TOKEN_END;
"do"    return TOKEN_DO;
"if"    return TOKEN_IF;
"else"  return TOKEN_ELSE;
"=="    {yylval.op = *yytext; return TOKEN_OPERATOR;}
"!="    {yylval.op = *yytext; return TOKEN_OPERATOR;}
[a-zA-Z_][a-zA-Z0-9_]* {yylval.name = _strdup(yytext); return TOKEN_ID;}
[-]?[0-9]+    {yylval.val = atoi(yytext); return TOKEN_NUMBER;}
[()=;]  {return *yytext;}
"<="    {yylval.op = *yytext; return TOKEN_OPERATOR;}
">="    {yylval.op = *yytext; return TOKEN_OPERATOR;}
[*/+-<>] {yylval.op = *yytext; return TOKEN_OPERATOR;}
[ \t\n] {/* suppress the output of the whitespaces from the input file to stdout */}
#.* {/* one-line comment */}

%%

我在这里做错了什么？

Answer 1

您错过了%type的{{1}}声明，因为来自bison的错误消息告诉您：

ifStmt

将t.y:46.17-18: $1 of `statement' has no declared type t.y:58.78-79: $$ of `ifStmt' has no declared type t.y:58.92-93: $3 of `ifStmt' has no declared type添加到第23行的声明ifStmt将修复前2个错误;可以使用%type<ast>代替$4修复第三个。

简单的Bison文件无法编译

1 个答案: