From: Linus Torvalds <torvalds@linux-foundation.org>
To: Jon Mason <jdmason@kudzu.us>, Dan Carpenter <dan.carpenter@oracle.com>
Cc: Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
linux-ntb@googlegroups.com
Subject: Re: [GIT PULL] NTB bug fixes for v5.11
Date: Sun, 27 Dec 2020 09:42:06 -0800 [thread overview]
Message-ID: <CAHk-=wgdcA-gADjaqp5KZChRjwKGStOo_MVEu3MSi7HiRDGS9g@mail.gmail.com> (raw)
In-Reply-To: <CAHk-=wjxQzF3eWank1r7F6+EqSRsO+kvibPqDbzxjHv3wzZt0A@mail.gmail.com>
On Sun, Dec 27, 2020 at 9:38 AM Linus Torvalds
<torvalds@linux-foundation.org> wrote:
>
> The thing is, "PTR_ERR()" works just fine on a IS_ERR_OR_NULL pointer.
> It doesn't work on a _regular_ non-NULL and non-ERR pointer, and will
> return random garbage for those. But if you've tested for
> IS_ERR_OR_NULL(), then a regular PTR_ERR() is already fine.
Side note: no, standard C does not guarantee that a NULL pointer would
cast to the integer 0 (despite a cast of the constant 0 turning into
NULL), but the kernel very much does. And our ERR_PTR() games in
particular already violate all the standard C rules, and we very much
depend on the pointer bit patterns to begin with.
Linus
next prev parent reply other threads:[~2020-12-27 17:42 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-12-27 14:16 [GIT PULL] NTB bug fixes for v5.11 Jon Mason
2020-12-27 17:27 ` pr-tracker-bot
2020-12-27 17:38 ` Linus Torvalds
2020-12-27 17:42 ` Linus Torvalds [this message]
2021-01-04 8:29 ` Dan Carpenter
2021-01-04 15:41 ` Jon Mason
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