From: Arnd Bergmann <arnd@arndb.de>
To: Oleg Nesterov <oleg@redhat.com>
Cc: Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
Nick Desaulniers <ndesaulniers@google.com>,
"Eric W . Biederman" <ebiederm@xmission.com>,
Alexander Viro <viro@zeniv.linux.org.uk>,
linux-arch <linux-arch@vger.kernel.org>,
Ralf Baechle <ralf@linux-mips.org>,
Paul Burton <paul.burton@mips.com>,
James Hogan <jhogan@kernel.org>,
Andrew Morton <akpm@linux-foundation.org>,
Deepa Dinamani <deepa.kernel@gmail.com>,
Christian Brauner <christian@brauner.io>,
"Gustavo A. R. Silva" <gustavo@embeddedor.com>,
linux-mips@vger.kernel.org
Subject: Re: [PATCH] signal: fix building with clang
Date: Thu, 7 Mar 2019 16:37:42 +0100 [thread overview]
Message-ID: <CAK8P3a2fuD-UBJET_OBKekCxrTDpnAxb0Bpu2LCCXaVT3pXTMQ@mail.gmail.com> (raw)
In-Reply-To: <20190307152805.GA25101@redhat.com>
On Thu, Mar 7, 2019 at 4:28 PM Oleg Nesterov <oleg@redhat.com> wrote:
>
> On 03/07, Arnd Bergmann wrote:
> >
> > clang warns about the sigset_t manipulating functions (sigaddset, sigdelset,
> > sigisemptyset, ...) because it performs semantic analysis before discarding
> > dead code, unlike gcc that does this in the reverse order.
> >
> > The result is a long list of warnings like:
> >
> > In file included from arch/arm64/include/asm/ftrace.h:21:
> > include/linux/compat.h:489:10: error: array index 3 is past the end of the array (which contains 2 elements) [-Werror,-Warray-bounds]
> > case 2: v.sig[3] = (set->sig[1] >> 32); v.sig[2] = set->sig[1];
>
> stupid question... I have no idea if this can work or not, but may be we can just do
>
> --- x/Makefile
> +++ x/Makefile
> @@ -701,6 +701,7 @@ KBUILD_CPPFLAGS += $(call cc-option,-Qun
> KBUILD_CFLAGS += $(call cc-disable-warning, format-invalid-specifier)
> KBUILD_CFLAGS += $(call cc-disable-warning, gnu)
> KBUILD_CFLAGS += $(call cc-disable-warning, address-of-packed-member)
> +KBUILD_CFLAGS += $(call cc-disable-warning, array-bounds)
> # Quiet clang warning: comparison of unsigned expression < 0 is always false
> KBUILD_CFLAGS += $(call cc-disable-warning, tautological-compare)
> # CLANG uses a _MergedGlobals as optimization, but this breaks modpost, as the
>
> ?
I would definitely not go that far, since the warning is generally
rather useful,
but we could try something more localized
__diag_push();
__diag_ignore(clang, 7, "-Warray-bounds");
...
__diag_pop();
> > I turn the nice switch()/case statements
> > into preprocessor conditionals, and where that is not possible, use the
> > '%' operator
>
> I can't say what looks worse... to me it would be either use ifdef's or %'s
> everywhere in signal.h, with this patch the code doesn't look consistent.
> But I won't insist.
I tried using just #ifdefs, but that did not work inside of macros.
We could use % everywhere, or possible wrap it inside of another
macro.
Arnd
next prev parent reply other threads:[~2019-03-07 15:38 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-03-07 9:11 [PATCH] signal: fix building with clang Arnd Bergmann
2019-03-07 10:03 ` Christian Brauner
2019-03-07 15:28 ` Oleg Nesterov
2019-03-07 15:37 ` Arnd Bergmann [this message]
2019-03-07 16:46 ` Oleg Nesterov
2019-03-07 18:41 ` Nick Desaulniers
2019-03-07 21:45 ` Arnd Bergmann
2019-03-08 0:22 ` Nick Desaulniers
2019-03-08 0:27 ` Joe Perches
2019-03-08 21:09 ` Nick Desaulniers
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