glr & locations

[Claudia Hermann]

hi all,

i have a parser with glr activated and use the location tracking 
function. every things works fine as long as i don't use ambiguous rules 
where i have to choose between with '%dprec'. additionally i have an 
optional nonterminal at the beginning of the rule. in this special case 
i get undefined values for the optional nonterminal as well as for the 
whole rule. In all other rules an empty nonterminal gets the location 
from the previous node.

i compiled the attached example with bison 2.1 and gcc 3.4.2. my system 
is freebsd 5.3 on i386. previously i also tried to compile with bison 
2.0, but with the same result.

when i execute this program, i get the following column locations for 
the 3 nodes:
0/4 - 671435522/671435522 - 6/8

but i would expect following result:
0/4 - 4/4 - 6/8

is this a bison bug or is there only any error in my code?
if this is a bug, does there any patch exist?

regards,
claudia hermann

%{
  static void yyerror(const char *msg);
  int i = 0;
%}


%token T_CONSTANT
%token T_PORT
%token T_SIGNAL

%glr-parser

%%


PortClause      : T_PORT InterfaceDeclaration T_PORT
                { printf("%d/%d - %d/%d - %d/%d\n", @1.first_column, 
@1.last_column, @2.first_column, @2.last_column, @3.first_column, 
@3.last_column); }
        ;

InterfaceDeclaration    : OptConstantWord       %dprec 1
        | OptSignalWord %dprec 2
        ;

OptConstantWord : /* empty */
        | T_CONSTANT
        ;

OptSignalWord   : /* empty */
                { printf("empty: %d/%d\n", @$.first_column, @$.last_column); }
        | T_SIGNAL
        ;

%%

static void yyerror(const char *msg) {
  fprintf (stderr, "error\n");
}

int yylex() {
  if (i == 0) {
    yylloc.first_column = 0;
    yylloc.last_column = 4;
    i++;
    return T_PORT;
  }

  if (i == 1) {
    yylloc.first_column = 6;
    yylloc.last_column = 8;
    i++;
    return T_PORT;
  }

  return 0;
}


int main (int argc, const char *argv[]) {
  yyparse();
  return 0;
}