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From: Linus Torvalds <torvalds@linux-foundation.org>
To: Alexander Potapenko <glider@google.com>
Cc: Evgenii Stepanov <eugenis@google.com>,
	Kees Cook <keescook@chromium.org>, Marco Elver <elver@google.com>,
	Nathan Chancellor <nathan@kernel.org>,
	Nick Desaulniers <ndesaulniers@google.com>,
	Thomas Gleixner <tglx@linutronix.de>,
	Vitaly Buka <vitalybuka@google.com>,
	Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
	linux-toolchains <linux-toolchains@vger.kernel.org>
Subject: Re: [PATCH] [RFC] Initialization of unused function parameters
Date: Tue, 14 Jun 2022 11:30:47 -0700	[thread overview]
Message-ID: <CAHk-=whjz3wO8zD+itoerphWem+JZz4uS3myf6u1Wd6epGRgmQ@mail.gmail.com> (raw)
In-Reply-To: <CAG_fn=WEed5NJ8hdrrP_N8aQ_1Ad11VoJgdVxQheo3VfT_xyXQ@mail.gmail.com>

On Tue, Jun 14, 2022 at 11:08 AM Alexander Potapenko <glider@google.com> wrote:
>
> On Tue, Jun 14, 2022 at 6:48 PM Linus Torvalds
> >
> > I'm assuming you mean pass by reference.
>
> No, sorry for being unclear. I mean passing by value.

Pass-by-value most definitely should warn about uninitialized variables.

> In the given example the prototype of step_into looks as follows (see
> https://elixir.bootlin.com/linux/latest/source/fs/namei.c#L1846):
>
>   static const char *step_into(struct nameidata *nd, int flags, struct
> dentry *dentry, struct inode *inode, unsigned seq);
>
> , and the local variables `struct inode *inode` and `unsigned seq` are
> being passed to it by value, i.e. in certain cases the struct inode
> pointer and the unsigned seq are uninitialized.

Then those cases should warn. No question about it.

I assume the only reason they don't warn right now is that the
compiler doesn't see that they are uninitialized, possibly due to some
earlier pass-by-reference use.

             Linus

  reply	other threads:[~2022-06-14 18:31 UTC|newest]

Thread overview: 14+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-06-14 14:48 [PATCH] [RFC] Initialization of unused function parameters Alexander Potapenko
2022-06-14 16:48 ` Linus Torvalds
2022-06-14 17:11   ` Nick Desaulniers
2022-06-14 17:24     ` Linus Torvalds
2022-06-14 18:08       ` Nick Desaulniers
2022-06-14 22:27         ` Peter Zijlstra
2022-06-14 18:07   ` Alexander Potapenko
2022-06-14 18:30     ` Linus Torvalds [this message]
2022-06-14 20:19       ` Alexander Potapenko
2022-06-14 20:43         ` Linus Torvalds
2022-06-14 21:40         ` Segher Boessenkool
2022-06-14 22:08           ` Evgenii Stepanov
2022-06-15  8:30           ` Alexander Potapenko
2022-06-15 16:46             ` Segher Boessenkool

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