Re: Getting a virtual functions VT lookup index

[Brendon Costa <brendon at christian dot net>]

Brendon Costa wrote:
> Hi all,
> 
> How can I find a FUNCTION_DECL node from a CALL_EXPR node for virtual
> function calls?
> 

Well I have managed to achieve this, though I don't know if it is the
best way to do so. For the sake of people that may find this question in
the list archives I will show how i did this.

>From a CALL_EXPR node, i get TREE_OPERAND(call_expr, 0). If this is a
OBJ_TYPE_REF then this is either a virtual function call or a function
pointer call to a class member (Maybe something else too but I cant
think what).





ref = TREE_OPERAND(call_expr, 0);
/* Get the INTEGER_CST node that contains the index to virtual function
lookup table */
virt_index = TREE_OPERAND(ref, 0);


/* Get the type of the class which this method belongs to */
pointer_type = TREE_TYPE(TREE_OPERAND(call_expr, 0));
method_type = TREE_TYPE(pointer_type);
class_type = TYPE_METHOD_BASETYPE(method_type);

virt_list = BINFO_VIRTUALS(TYPE_BINFO(class_type));
for (virt = virt_list; virt; virt = TREE_CHAIN(virt))
{
   fndecl = BV_FN(virt);
   index = DECL_VINDEX(fndecl);

   !! Now if index and virt_index are the same then fndecl is the
FUNCTION_DECL node for the virtual function being called. !!
}


I hope this might help someone. Also if anyone can see a major problem
in this code or a much better way of doing this I would love to hear it.

I discovered mostly through trial and error so there is a chance that it
could be completely incorrect.

Brendon.