我正在尝试为迷你 Pascal 语言制作一个编译器。我为此使用了 Flex 和 Bison,并且出现了这个错误。
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;
}
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");
}
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
$
关于声明什么以及在哪里导致我声明某些内容的方式错误的任何建议!
仅仅声明还不够yyerror
。您必须提供定义。
The 野牛手册 http://www.gnu.org/software/bison/manual/html_node/Error-Reporting.html建议以下作为最低限度的实施:
void yyerror (char const *s) {
fprintf (stderr, "%s\n", s);
}
你遇到的另一个问题是你拼写错误strcpy
在你的 Flex 文件中。
更准确地说,链接器错误揭示的另一个问题是拼写错误strcpy
,因为您复制的代码不正确。它没有考虑到NUL
必须终止字符串的字节。strcpy
将复制该字节,结果它将写入0
在未分配的存储中。你会发现使用起来更加简单strdup
。 (不要忘记你需要free
当你用完琴弦后,再把它们拉出来。)
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