Question

I’m using ANTLR generated c parser in my C++ program and I wish to use my helper class in parser to write something like the following:

constant_declaration 
:   'const' type_specifier ID ('[' constant_expression ']')? '=' initializer
    {
        parserHelper->addConstant($type_specifier.text, $ID.text);
    }
;

Where parserHelper is my C++ helper object. But I’m stuck with passing this helper to the C parser. In object oriented languages the simple way is to use base parser class. It is not possible in C. The only solution I came for now is to define global variable in @members section and initialize it before parsing:

@members
{
    ParserHelper* parserHelper;
}

For some reasons this is inconvenient for me. Isn’t there a way to put this variable into C parser structure generated by ANTLR?

Answer 1

One possible solution is to use ANTLR named scopes instead of a global member section.

The following implementation should correspond to what you are looking for:

scope GlobalScope
{
    ParserHelper* parserHelper;
}

rootRule
scope GlobalScope
@init {
  // Initialize the scope attributes
  // Somehow retrieve or create a PointerHelper (you can eventually pass it by an argument of the rootRule)
  $GlobalScope::parserHelper = ...;
}
:
...
;

constant_declaration 
:   'const' type_specifier ID ('[' constant_expression ']')? '=' initializer
    {
        $GlobalScope::parserHelper->addConstant($type_specifier.text, $ID.text);
    }
;