On Tue, Apr 14, 2020 at 11:19:32AM -0700, Linus Torvalds wrote:
> On Tue, Apr 14, 2020 at 12:49 AM Luc Van Oostenryck
> <luc.vanoostenryck@xxxxxxxxx> wrote:
> >
> > The problem is that now normal labels use the new label_scope
> > but the ones declared with __label__ use block_scope and these
> > 2 scopes are kinda in a different namespace of scope.
>
> Oh, I forgot about the special __label__ thing that actually declares labels.
>
> That one has an interesting behavior, in that the _lifetime_ of the
> symbol is the block scope, but the *use* of the symbol must remain in
> label scope.
>
> The most obvious fix is probably something like the appended: make the
> 'sym->scope' remain the lifetime scope, but then attach a "must be
> used in this scope' thing to any NS_LABEL case.
>
> That fairly clearly separates the two issues.
Yes, I see the principle but ... it doesn't work yet for __label__
and the more I think about it, the more I think it can't work.
The problem is that the block scopes and the label scopes are
never comparable. At the syntax level the label scope is a subset
of the block levels, less fine grained but for sparse 'struct scope'
they are never the same, even for the same { }.
So, in your patch (with things removed for simplicity):
diff --git a/parse.c b/parse.c
index 8e238f59..b6109516 100644
--- a/parse.c
+++ b/parse.c
@@ -2541,13 +2542,14 @@ static struct token *statement(struct token *token, struct statement **tree)
- if (s->scope != label_scope) {
- sparse_error(stmt->pos, "label '%s' used outside label expression", show_ident(s->ident));
+ if (s->scope != s->declared_scope) {
This comparison can never succeed for labels declared with __label__
because s->scope is a block scope and s->declared_scope a label one.
I'm sure it's fixeable in some way and problably it's just me
having a kind of 'mental blocage' but I don't see how the
normal scoping with lookup_symbol() can be really useful for
labels without losing the conceptual simplicity or without going
to something like my previous solution.
-- Luc
