From mboxrd@z Thu Jan  1 00:00:00 1970
From: Christopher Li <sparse@chrisli.org>
Subject: Re: [PATCH] Do not drop 'nocast' modifier when taking the address.
Date: Wed, 3 Feb 2016 12:09:16 +0800
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To: Luc Van Oostenryck <luc.vanoostenryck@gmail.com>
Cc: Fengguang Wu <fengguang.wu@intel.com>, Paolo Bonzini <pbonzini@redhat.com>, Roman Kagan <rkagan@virtuozzo.com>, "Denis V. Lunev" <den@openvz.org>, Andrey Smetanin <asmetanin@virtuozzo.com>, Linux-Sparse <linux-sparse@vger.kernel.org>, Linus Torvalds <torvalds@linux-foundation.org>, Martin Schwidefsky <schwidefsky@de.ibm.com>

On Wed, Feb 3, 2016 at 11:43 AM, Luc Van Oostenryck
<luc.vanoostenryck@gmail.com> wrote:
pped.
>
> The nocast mod is dropped and lost in the function create_pointer().
> In the example above, "cputime_t *" has type :
>         unsigned long [nocast] [usertype] *
> while &utime is just:
>         unsigned long *

That is my point. Why does "&utime" get drop but "cputime_t *" does not?
They both are pointer of a base type. They both create pointers.

It seems to me the bug is sparse not treating this two case consistently.

> So, for sparse and its extended notion of type, the type we get when
> taking the address of a [variable of some] type X is not the same as
> directly using a pointer to the type X.

In C language type system,  these two should be the same type. It is a
bug in sparse if they are not. I would rather get that bug fixed.

> Which is very fine, just that MOD_NOCAST is dropped while the example
> shows that it should not.

I think that is a separate issue weather MOD_NOCAST should be inherent
from pointer base type. Same with MOD_STORAGE.

Chris