使用Flex和Bison编译时未定义的“_yyerror”引用。

I'm trying to make a compiler for a mini Pascal-like language. I'm using Flex and Bison for this and I came up with this error.

我想让编译器变成一种小型的帕斯卡语言。我用Flex和Bison来做这个，我想出了这个错误。

My Flex file:

我的Flex文件:

%{
#include "y.tab.h"
#include <stdlib.h>
#include <string.h>
#include <math.h>
void yyerror(char *);
%}

%%

[1-9][0-9]*     {
                yylval.i = atoi(yytext);
                return INT;
}

program     return PROGRAM;
or          return OR;
and         return AND;
not         return NOT;
if          return IF;
else        return ELSE ;
while       return WHILE;
"+"         return PLUS;
"-"         return MINUS;
"*"         return MUL;
"/"         return DIV;
"["         return LSB;
"]"         return RSB;
"{"         return LCB;
"}"         return RCB;
"("         return LEFTPAR;
")"         return RIGHTPAR;
":="        return ASSIGN;
"=="        return ISEQUAL;
"<"         return LTHAN;
">"         return GTHAN;
"<>"        return NOTEQUAL;
"<="        return LESSEQUAL;
">="        return GREATEREQUAL;

[a-zA-z][a-z0-9]*   {
                    yylval.s = (char*)malloc(strlen(yytext)*sizeof(char));
                    strcopy(yylval.s,yytext);
                    return ID;
}               

[ \t\n]+                            /* eat up whitespace */         

.                                   yyerror("Unknown Character");

%%
int yywrap(void) {
    return 1;
}

My Bison file:

我的野牛文件:

%{
    #include <stdio.h>
    #include <string.h>
    int yylex(void);
    void yyerror(char *s);
%}

%union {
    int i;
    char *s;
};

%token <i> INTEGERNUM

%token PROGRAM;
%token OR;
%token AND;
%token NOT;
%token IF;
%token ELSE;
%token WHILE;
%token PLUS;
%token MINUS;
%token MUL;
%token DIV;
%token LSB;
%token RSB;
%token LCB;
%token RCB;
%token LEFTPAR;
%token RIGHTPAR;
%token ID;
%token INT;
%token ASSIGN;
%token ISEQUAL;
%token LTHAN;
%token GTHAN;
%token NOTEQUAL;
%token LESSEQUAL;
%token GREATEREQUAL;

%%

program:
        PROGRAM ID block
        ;

block:
        LCB sequence RCB
        ;

sequence:
        statement ';' sequence
        | statement ';' 
        ;

bracketsSeq:
        LCB sequence RCB
        ;

brackOrStat:        
        bracketsSeq
        | statement
        ;

statement:
        assignmentStat
        |ifStat
        |whileStat
        |
        ;

assignmentStat:
        ID ':=' expression

ifStat:
        IF LEFTPAR condition RIGHTPAR brackOrStat elsepart
        ;

elsepart:
        ELSE brackOrStat
        |
        ;

whileStat:
        WHILE LEFTPAR condition RIGHTPAR brackOrStat
        ;

expression:
        optionalSign expression
        |expression addOper expression
        |term
        ;

term:
        term mulOper term
        |factor
        ;

factor:
        INT
        |LEFTPAR expression RIGHTPAR
        |ID
        ;

condition:
        condition AND condition
        |boolterm
        ;

boolterm:
        boolterm OR boolterm
        |boolfactor
        ;

boolfactor:
        NOT LSB condition RSB
        |LSB condition RSB
        |expression relationalOper expression
        ;

relationalOper:
        ISEQUAL
        |LTHAN
        |GTHAN
        |NOTEQUAL
        |LESSEQUAL
        |GREATEREQUAL
        ;

addOper:
        PLUS
        |MINUS
        ;

mulOper:
        MUL
        |DIV
        ;

optionalSign:
        addOper
        |
        ;

%%

int main( int argc, char **argv )
             {
             printf("TEST\n");

             }

The series of steps I executed was:

我执行的一系列步骤是:

$ ./bison.exe -dy comp.y
$ ./flex.exe comp.l
$ gcc -c -w lex.yy.c 
$ gcc -c -w comp.tab.c
$ gcc comp.tab.o lex.yy.o -o ex
comp.tab.o:comp.tab.c:(.text+0x4cd): undefined reference to `_yyerror'
comp.tab.o:comp.tab.c:(.text+0x61c): undefined reference to `_yyerror'
lex.yy.o:lex.yy.c:(.text+0x34a): undefined reference to `_strcopy'
lex.yy.o:lex.yy.c:(.text+0x362): undefined reference to `_yyerror'
/usr/lib/gcc/i686-pc-cygwin/3.4.4/../../../../i686-pc-cygwin/bin/ld: lex.yy.o: bad reloc address                0x828 in section `.rdata'
/usr/lib/gcc/i686-pc-cygwin/3.4.4/../../../../i686-pc-cygwin/bin/ld: final link failed: Invalid                operation
collect2: ld returned 1 exit status
$

Any advice as to what to declare and where cause there seems to be that I have declared something the wrong way!

关于该声明什么，以及在什么地方引起的任何建议，似乎我已经声明了错误的方式!

1 个解决方案

#1

It's not enough to declare yyerror. You must provide a definition.

仅仅声明yyerror是不够的。您必须提供一个定义。

The bison manual suggests the following as a minimal implementation:

bison手册建议将以下内容作为最小的实现:

 void yyerror (char const *s) {
   fprintf (stderr, "%s\n", s);
 }

The other problem you have is that you misspelled strcpy in your flex file.

另一个问题是在flex文件中拼写错误。

More accurately, the other problem revealed by the linker errors is the misspelled strcpy, because your copying code is incorrect. It does not account for the NUL byte which must terminate strings. strcpy will copy that byte, with the result that it will write a 0 in unallocated storage. You'll find it much simpler to use strdup. (And don't forget that you need to free the strings when you're finished with them.)

更准确地说，链接器错误显示的另一个问题是拼写错误的strcpy，因为您的复制代码是错误的。它不考虑必须终止字符串的NUL字节。strcpy将复制该字节，结果将在未分配的存储中写入0。您会发现使用strdup更简单。(别忘了，当你完成这些字符串时，你需要释放它们。)

#1