Question

I am writing a front end for my C compiler, where in I am adding Type system currently. Previously I assumed everything was an int and hence the following rule worked fine.

declaration: datatype varList ';' { gTrace<<"declaration ";}

varList: IDENTIFIER { builder.addSymbol($1); }
    | varList',' IDENTIFIER { builder.addSymbol($3); }
    ;

But now I also add type to the symbol, and hence modified my rule like below:

 declaration: datatype { currentType = $1; } varList ';' { gTrace<<"declaration ";   currentType = -1; }

 varList: IDENTIFIER    { builder.addSymbol($1, getType(currentType)); }
    | varList',' IDENTIFIER { builder.addSymbol($3, getType(currentType)); }
    ;

I get a shift/reduce error when I do that, since the { currentType = $1; } is being considered as an empty rule. How do I go about this error? Is there a way to specify that it is just an action?

Attached below is a snippet from my y.output

32 $@6: /* empty */

33 declaration: datatype $@6 varList ';'

34 varList: IDENTIFIER
35        | varList ',' IDENTIFIER

Answer 1

I fixed the problem as below:

declaration: datatype varList ';' { gTrace<<"declaration "; currentType = -1; }

varList: IDENTIFIER { builder.addSymbol($1, getType(currentType)); }
    | varList',' IDENTIFIER { builder.addSymbol($3, getType(currentType)); }
    ;

datatype: INTEGER   { gTrace<<"int "; $$ = currentType = Type::IntegerTy; }
    | FLOAT     { gTrace<<"float "; $$ = currentType = Type::FloatTy; }
    | VOID      { gTrace<<"void "; $$ = currentType = Type::VoidTy; }
    ;

@sarnold, hope this helps!