bison和flex的分割错误

问题描述

我正在尝试使用oreilly书学习lex和yacc.我尝试了本书中的以下示例，但它给出了细分错误.

I was trying learn lex and yacc using the oreilly book. I tried following example from book, but it gives segmentation fault.

%{
 /**
  * A lexer for the basic grammar to use for recognizing English sentences.
  */

  #include <stdio.h>
  extern FILE *yyin;
%}

%token NOUN PRONOUN VERB ADVERB ADJECTIVE PREPOSITION CONJUNCTION

%%
sentence: subject VERB object{ printf("Sentence is valid.\n");}
 ;

subject: NOUN
 | PRONOUN
 ;
object:  NOUN
 ;
%%


main()
{
 while(!feof(yyin)) {
  yyparse();
 }

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

我正在使用flex和bison.在while循环中，我在主函数中遇到分段错误.它根本没有进入循环.

i'm using flex and bison.I'm getting segmentation fault in main function, in the while loop. It is not entering at all to the loop.

有什么想法吗?谢谢，罗伯特

Any thoughts?Thanks,Robert

推荐答案

yyin是否真的在某个地方给出了有意义的值?也许尝试分配它:

Is yyin actually given a meaningful value somewhere? Perhaps try assigning it:

yyin = stdin;

就在主循环之前.

并且可能尝试不将其定义为外部"，除非它实际上是在其他地方定义的.

and maybe try not defining it "extern" unless it's actually defined somewhere else.

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