Bison perhaps has a bug.

[Supervisor Root]

I used bison2.4.1, yacc1.9.1 and flex2.5.4 to create a simple parser under 
windows XP platform, but I found that yyparse return zero when syntax is error, 
this is or not a bug?

 

The parser's yacc grammar is as follows:

 

/*statement.flex*/
/*
*/

%{
#include <stdio.h>
#include "y.tab.h"
%}
%%
[ \t]+ ;
[\n]+ ;
if return IF;
else return ELSE;
print return PRINT;
true {yylval.value = 1; return TRUE;}
false {yylval.value = 1; return FALSE;}
[1-9][0-9]+ {yylval.value = atoi(yytext); return NUMBER;}
. return yytext[0];
%%
int yywrap(void)
{
 return 1;
}

 

/*
statement
*/
%{
#include <stdio.h>
%}
%union
{
 int value;
}

%token IF ELSE PRINT
%token <value> NUMBER TRUE FALSE
%type <value> condition
%%
program: statement_list
 ;

statement_list: statement_list statement
  |  statement

statement: IF condition statement 
   {
    printf("single if statement.\n");
   }
  |  IF condition statement ELSE statement 
   {
    printf("if else statement.\n");
   }
  |  PRINT NUMBER ';' 
   {
    printf("number = %d\n", $2);
   }
  | '{' statement_list '}'   
   {
    printf("compound statement.\n");
   }
  ;

condition: TRUE
 |  FALSE
 |  error {}
 ;

%%
extern FILE *yyin;
extern char *yytext;
int main(int argc, char *argv[])
{
 int nRet;
    if (argc < 2)
   return 1;
 yyin = fopen(argv[1], "r");
 nRet = yyparse();
 if (nRet == 0)
 {
  printf("This is a corrent program!\n");
 }
 else
 {
  printf("This is a incorrent program!\n");
 }
 return 0;
}
int yyerror(const char *str)
{
 fprintf(stdout, "yytext = %s, %s\n", yytext, str);
 return 0;
}

 

The parser's flex grammar is as follows:

 


/*
*/

%{
#include <stdio.h>
#include "y.tab.h"
%}
%%
[ \t]+ ;
[\n]+ ;
if return IF;
else return ELSE;
print return PRINT;
true {yylval.value = 1; return TRUE;}
false {yylval.value = 1; return FALSE;}
[1-9][0-9]+ {yylval.value = atoi(yytext); return NUMBER;}
. return yytext[0];
%%
int yywrap(void)
{
 return 1;
}

 

In addition, the parser runs normal under linux platform. (yyparse returns 
non-zero under linux platform, but yyparse return zero in windows xp platform, 
why? It it a bug?

 

Who can explain the cause?

 

Best regards,

 

2009-02-08
                                          
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