Unable to use error recovery with bison

f.tomassetti@gmail.com (Federico Tomassetti)
11 Apr 2005 00:15:41 -0400

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From: f.tomassetti@gmail.com (Federico Tomassetti)
Newsgroups: comp.compilers
Date: 11 Apr 2005 00:15:41 -0400
Organization: http://groups.google.com
Keywords: parse, yacc, errors

I spent the last days trying to make error recovery working but I
can't catch one and yyerror is always invoked:


I report a portion from the lex source, yacc source and file parsed.


I always obtain the message "syntax error, unexpected NEWLINE,
expecting SPACE"


I use bison 2.0 and flex 2.5.31


(I'm a bit frustrated so tryed to pollute my code with "error" to
solve the problem but seems it not worked...)


YACC SOURCE
-----------


start: /* empty */
| components
;


components:
| components component
| components voidspace
| error voidspace { printf("ERROR\n"); }
| error ENDOFFILE { printf("ERROR\n"); }
;


voidspace: SPACE | TAB | NEWLINE
;


component: class_decl
| error voidspace { printf("ERROR\n");}
| error NEWLINE { printf("ERROR\n"); }
| error ENDOFFILE { printf("ERROR\n"); }
;


class_decl: class_decl_header block_decls NEWLINE KWENDC
{
if (State::verbose_) {
print_pos();
printf("Exiting decl of class %s\n", $1);
}
}
| class_decl_header error KWENDC {printf("E\n");};
;


class_decl_header:
KWCLASS SPACE CLASSNAME
{
$$=$3;


if (State::verbose_) {
print_pos();
std::cout << "Entering decl of class " << $3 << std::endl;
}


try_start_class_decl( std::string( $3 ), pos_line, pos_char );
}
| KWCLASS error { printf("ciao\n");fflush(stdout);} NEWLINE
| error { printf("ciao\n");fflush(stdout);}
| KWCLASS error voidspace { printf("1a\n");}
| error voidspace { printf("1a\n");}
| error NEWLINE { printf("1a\n");}
| KWCLASS error NEWLINE { printf("1a\n");}
;




LEX SOURCE
----------


  /* Save the whole line */


  ^.*/\n {
char str[MAXLINELENGTH+30];
snprintf(str, MAXLINELENGTH+30, "LINE READ (%s)", yytext);
verbose_info( str );
strncpy(current_line,yytext,MAXLINELENGTH);
REJECT;
  }


  /* Comments */


"//".*\n {
// ignore comments
}


  /* Keywords */


"class" {
increment_len( strlen(yytext), 0 );
verbose_info("CLASS");
return KWCLASS;
}


"endc" {
increment_len( strlen(yytext), 0 );
verbose_info("ENDC");
return KWENDC;
}


"block" {
increment_len( strlen(yytext), 0 );
verbose_info("BLOCK");
return KWBLOCK;
}


[A-Z]+[_[A-Z]+]* {
char str[100];
increment_len( strlen(yytext), 0 );
snprintf( str, 100, "classname(%s)\n", yytext);
verbose_info( str );
yylval.string=strdup(yytext);
return CLASSNAME;
}


[a-z]+[_[a-z]+]* {
char str[100];
increment_len( strlen(yytext), 0 );
snprintf( str, 100, "methodname(%s)\n", yytext);
verbose_info( str );
yylval.string=strdup(yytext);
return METHODNAME;
}


"\n" {
increment_len( 0, 1 );
verbose_info( "NEWLINE" );
return NEWLINE;
}


\t {
increment_len( TABSIZE, 0 );
verbose_info("TAB");
return TAB;
}


\b {
   increment_len( strlen(yytext), 0 );
verbose_info("SPACE");
   return SPACE;
}


  <<EOF>> {
increment_len(0,0); /* causa aggiornamento posizione */
verbose_info( "ENDOFFILE" );
   return ENDOFFILE;
}


. {
char str[100];
   increment_len( strlen(yytext), 0 );
snprintf( str, 100, "unexpected char (%c)\n", yytext[0]);
verbose_info(str);
lex_error(str);
}


/* Example file */
------------------
class


class






class
------------------


Thanks in advance for the help you can give me,


Federico Tomassetti



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