Multiple attributes in bison

Question

I am doing semantic analysis in bison and i want to use multiple attribute associated with a token. A related part of my code is:

%union semrec
{
    int Type;
    char *id;

}

%start prog

%token <id>  tIDENT

Here, i can only use the "id" attribute witht the tIDENT token. I also want to associate the "Type" attribute with tIDENT token. To do this, i tried the following:

 %token <id>  tIDENT
 %token <Type>  tIDENT

But it gives me a redeclaration warning for token tIDENT. I also tried the following:

 %token <id> <Type> tIDENT

It also did not work. What can i do? I think this is just a little syntactic problem.

Thank you.

Answer 1

You cannot do it this way: you have to define your %union in such a way that all the symbols that have multiple "attributes" have a struct to define all these "attributes". Something like

%union
{
  struct
  {
    int type;
    char *id;
  } type_id;
}
%type <type_id> tIDENT

and use $1.type or $1.id etc.

Note however that I very much doubt that you're doing the right thing. Chances are high that you will need an AST (Abstract Syntax Tree). You should look for information about that.