On Fri, Mar 22, 2013 at 1:44 PM, Gabriel Dos Reis <[email protected]> wrote:
> Richard Biener <[email protected]> writes:
>
> [...]
>
> | > in the C++ front-end. identifier_p is effectively LANG_IDENTIFIER_CAST
> | > except that it returns a typed pointer instead of a boolean value.
> |
> | Hm? So you are replacing TREE_CODE (t) == IDENTIFIER_NODE
> | with kind-of dynamic_cast<identifier> (t) (in C++ terms)?
>
> It would be a mistake to name it dynamic_cast or anything like cast (I
> know it is popular in certain C++ circles to name everything xxx_cast),
> because dynamic_cast is an implementation detail. I should probably
> have called it
> "give_me_identifier_pointer_if_operand_points_to_a_cxx_identifier_object"
>
> | Then
> | naming it identifier_p is bad. We have is-a.h now, so please try to use
> | a single style of C++-style casting throughout GCC.
>
> I strongly agree with consistent style, On the other hand, isn't someone
> going
> to object that is_xxx has a predicate connotation therefore a bad naming
> because it isn't returning a bool?
>
> I think a naming that focuses too much on implementation detail is no good,
Neither is one that is confusing ;)
That said - your specific identifier case should be generalized. The cgraph
people had exactly the same issue, given a symtab * return a cgraph *
if the symbol is a function, otherwise NULL, combining the previous
if (symbol == function) fn = get-me-a-function (symbol)
And they invented is-a.h as we settled for a template approach which
more readily mimics what the C++ language provides (in form of
static_cast<>, dynamic_cast<>, etc.).
The tree node case is subtly different because we are not actually casting
anything (you are not returning a more specific type than tree) but still
you provide a more C++-ish form to the standard tree.h interfaces.
That is, plain use of is-a.h is possible for your case:
template <>
inline lang_identifier *
as_a (tree p)
{
if (TREE_CODE (p) == IDENTIFIER_NODE)
return (lang_identifier *)p;
return NULL;
}
following existing GCC style (and yes, we've bikeshedded over that
already).
Thus you'd write
as_a<lang_identifier> (id)
instead of your
identifier_p (id)
(which should have been lang_identifier_p instead).
Richard.
> -- Gaby
