无法编译flex&野牛(找不到符号x86_64) [英] Can't compile flex & bison (Symbols not found x86_64)

问题描述

我正在尝试在Flex& amp;上编译一个简单的程序.运行优胜美地的Mac上的野牛，但出现以下错误:

I am trying to compile a simple program on Flex & Bison on my Mac running Yosemite but get the following error:

体系结构x86_64的未定义符号: "_yyerror"，引用自: pr1-19c182.o中的_yyparse ld:找不到架构x86_64的符号 clang:错误:链接器命令失败，退出代码为1(使用-v查看调用)

Undefined symbols for architecture x86_64: "_yyerror", referenced from: _yyparse in pr1-19c182.o ld: symbol(s) not found for architecture x86_64 clang: error: linker command failed with exit code 1 (use -v to see invocation)

我的两个文件看起来像这样，它们在我老师的Ubuntu安装中编译，但是我无法在Mac上运行它们:

My two files look like this, they compile on my teacher's Ubuntu installation but I can't get them to work on my Mac:

pr1.y

%{
    #include <stdio.h>
%}

%%

expr : expr '+' term {printf(" + ");}
    | term 
    ;

term : term '*' fact {printf(" * ");}
    | fact 
    ;

fact : "(" expr ")"
    | '0' {printf("0");}
    | '1' {printf("1");}
    | '2' {printf("2");}
    | '3' {printf("3");}
    | '4' {printf("4");}
    | '5' {printf("5");}
    | '6' {printf("6");}
    | '7' {printf("7");}
    | '8' {printf("8");}
    | '9' {printf("9");}

%%

pr1.l

%{
    #include "pr1.tab.h"
%}

%%

[0-9]   {return (yytext[0]);}
[+*()]  {return (yytext[0]);}
\n      {return (0);}
.       {}

%%

我使用以下命令编译所有内容:

I compile everything using the following commands:

bison -d pr1.y
flex pr1.l
gcc -o result lex.yy.c pr1.tab.c -lfl -std=gnu89

我使用-std标志的原因是因为默认值是c99，而flex和bison生成的代码会得到警告和错误.有什么想法吗?

The reason I use the -std flag is because the default is c99 and the code generated by flex and bison gets warnings and errors. Any ideas???

推荐答案

您需要在野牛输入文件(pr1.y)中定义yyerror.并且您需要声明yylex否则您将收到另一个警告.

You need to define yyerror in your bison input file (pr1.y). And you need to declare yylex or you will get another warning.

以下内容会很好:

%{
   #include <stdio.h>
   void yyerror(const char* msg) {
      fprintf(stderr, "%s\n", msg);
   }
   int yylex();
%}

我不知道没有老师的机器怎么工作.

I have no idea how it works without that on your teacher's machine.

此外，Mac OS X具有非常老的bison和flex版本.您可能要升级.

Also, Mac OS X has very old versions of bison and flex. You might want to upgrade.

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