Re: A question about TYPE_ARG_TYPES

[Kazu Hirata <kazu at codesourcery dot com>]

Hi Ian,

> > I keep finding places in GCC sources that check whether a member of
> > TYPE_ARG_TYPES is 0.  For example,
> >
> >  for (link = TYPE_ARG_TYPES (function_or_method_type);
> >       link && TREE_VALUE (link);
> >       link = TREE_CHAIN (link))
> >    gen_type_die (TREE_VALUE (link), context_die);
> >
> > Notice that TREE_VALUE (link) is part of the loop condition.
> >
> > Now, do we ever allow a NULL in TYPE_ARG_TYPES?  If so, what does that
> > mean?  My guess is that soneone was trying to be cautious about
> > encountering a NULL in TYPE_ARG_TYPES.  (If that's the case, we should
> > be using gcc_assert instead.)
>
>
> Just guessing here, but what happens with an old-style function
> definition in C?
>
> void f();

AFAIK, that gets TYPE_ARG_TYPES (...) == NULL, so we don't even get to evaluate 
TREE_VALUE (TYPE_ARG_TYPES (...)).

On IRC, Daniel Berlin claims that there are some weird cases where TREE_VALUE 
(TYPE_ARG_TYPES (...)) is NULL.  I'll keep putting gcc_assert to see what happens.

Kazu Hirata