Re: [PATCH] uaccess: Fix build of scoped user access with const pointer

[Linus Torvalds]

On Sun, 1 Mar 2026 at 11:34, Christophe Leroy (CS GROUP)
<chleroy@xxxxxxxxxx> wrote:
>
> -       for (void __user *_tmpptr = __scoped_user_access_begin(mode, uptr, size, elbl); \
> +       for (void __user *_tmpptr = (void __user *)                                     \
> +                                   __scoped_user_access_begin(mode, uptr, size, elbl); \

Why are you casting this return value? Wouldn't it be a lot better to
just make the types be the CORRECT ones?

I didn't test this, so maybe I'm missing something, but why isn't that
just doing

        for (auto _tmpptr = __scoped_user_access_begin(mode, uptr,
size, elbl);         \

instead? No cast, just a "use the right type automatically".

That macro actually does something similar just a few lines later, in
that the innermost loop uses

         for (const typeof(uptr) uptr = _tmpptr; !done; done = true)

which picks up the type automatically from the argument (and then it
uses the argument both for the type and name, which is horrendously
confusing, but that's a separate thing).

Does that simple "auto" approach break something else?

                   Linus