From: Petr Mladek <pmladek@suse.com>
To: Rasmus Villemoes <linux@rasmusvillemoes.dk>
Cc: "Arnd Bergmann" <arnd@kernel.org>,
"Andrew Morton" <akpm@linux-foundation.org>,
"Uwe Kleine-König" <uwe@kleine-koenig.org>,
"Andy Shevchenko" <andy.shevchenko@gmail.com>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH] printf: fix Woverride-init warning for EDEADLK errno
Date: Tue, 27 Oct 2020 13:03:30 +0100 [thread overview]
Message-ID: <20201027120330.GD31882@alley> (raw)
In-Reply-To: <13d87c71-66b2-2abb-825d-6e8e2e47d22a@rasmusvillemoes.dk>
On Tue 2020-10-27 11:55:56, Rasmus Villemoes wrote:
> On 27/10/2020 10.12, Petr Mladek wrote:
> > On Tue 2020-10-27 09:46:28, Arnd Bergmann wrote:
> >> On Tue, Oct 27, 2020 at 8:23 AM Rasmus Villemoes
> >> <linux@rasmusvillemoes.dk> wrote:
> >>> On 26/10/2020 22.49, Arnd Bergmann wrote:
> >>>> From: Arnd Bergmann <arnd@arndb.de>
> >>>
> >>> NAK. That would end up using the "EDEADLOCK" string for the value 35 on
> >>> those architectures where they are the same, despite EDEADLK being the
> >>> by far the most used symbol. See the comments and original commit log,
> >>> the placement of these is deliberate.
> >
> > Good point.
> >
> >> Ok, I see.
> >>
> >>> How about we do this instead?
> >>>
> >>> when building with W=1. As the use of multiple initializers for the
> >>> same entry here is quite deliberate, explicitly disable that warning
> >>> for errname.o.
> >>>
> >>> diff --git a/lib/Makefile b/lib/Makefile
> >>> index ce45af50983a2a5e3582..a98119519e100103818d 100644
> >>> --- a/lib/Makefile
> >>> +++ b/lib/Makefile
> >>> @@ -224,6 +224,7 @@ obj-$(CONFIG_HAVE_ARCH_TRACEHOOK) += syscall.o
> >>>
> >>> obj-$(CONFIG_DYNAMIC_DEBUG_CORE) += dynamic_debug.o
> >>> obj-$(CONFIG_SYMBOLIC_ERRNAME) += errname.o
> >>> +CFLAGS_errname.o += $(call cc-disable-warning, override-init)
> >>>
> >>
> >> This works, but it disables a potentially useful warning in case we
> >> get another conflict in this file, so I'd prefer to find a way to
> >> avoid the warning rather than force-disabling it.
> >
> > Yeah, I think that it is better to explicitely disable the less used
> > variant in the code than hiding the double initialization. It will
> > be clear what is going on.
> >
> >
> >> How about adding the #ifdef around the EDEADLOCK line
> >> instead of the EDEADLK one? Something like
> >>
> >> diff --git a/lib/errname.c b/lib/errname.c
> >> index 0c4d3e66170e..93043fb960cc 100644
> >> --- a/lib/errname.c
> >> +++ b/lib/errname.c
> >> @@ -38,7 +38,10 @@ static const char *names_0[] = {
> >> E(ECOMM),
> >> E(ECONNABORTED),
> >> E(ECONNRESET),
> >> + E(EDEADLK), /* EDEADLOCK */
> >> +#if EDEADLK != EDEADLOCK /* mips, sparc, powerpc */
> >> E(EDEADLOCK),
> >> +#endif
> >> E(EDESTADDRREQ),
> >> E(EDOM),
> >> E(EDOTDOT),
> >> @@ -169,7 +172,6 @@ static const char *names_0[] = {
> >> E(ECANCELED), /* ECANCELLED */
> >> E(EAGAIN), /* EWOULDBLOCK */
> >> E(ECONNREFUSED), /* EREFUSED */
> >> - E(EDEADLK), /* EDEADLOCK */
> >
> > This should stay :-)
> >
>
> No, Arnd moved it next to EDEADLOCK, which is fine (it can lose the
> comment /* EDEADLOCK */, though; the comment on the ifdef is
> sufficient). Especially when:
>
> > And we should remove the ECANCELLED definition. It is always the same
> > as ECANCELED and replaced. We do not define EWOULDBLOCK and
> > EREFUSED either.
>
> Yes, I'm not sure why I elided EWOULDBLOCK and EREFUSED but not
> ECANCELLED. So let's move EAGAIN, ECONNREFUSED and ECANCELED to their
> proper alphabetic place. But I also want to add a check that the things
> we've elided match some value that we do handle. So add something like
>
> #ifdef EREFUSED /* parisc */
> static_assert(EREFUSED == ECONNREFUSED);
> #endif
>
> #ifdef ECANCELLED /* parisc */
> static_assert(ECANCELLED == ECANCELED);
> #endif
>
> static_assert(EAGAIN == EWOULDBLOCK); /* everywhere */
>
> so that if we ever import some arch that defines EREFUSED to something
> other than ECONNREFUSED, it would be caught. Essentially, errname.c
> should mention every #define E* that appears in any errno*.h.
Sounds like a good plan.
Arnd, are you going to take care of this or should we clean up it ourself?
Best Regards,
Petr
prev parent reply other threads:[~2020-10-27 12:03 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-10-26 21:49 [PATCH] printf: fix Woverride-init warning for EDEADLK errno Arnd Bergmann
2020-10-27 6:55 ` Uwe Kleine-König
2020-10-27 8:41 ` Arnd Bergmann
2020-10-27 7:23 ` Rasmus Villemoes
2020-10-27 7:25 ` Rasmus Villemoes
2020-10-27 8:46 ` Arnd Bergmann
2020-10-27 9:12 ` Petr Mladek
2020-10-27 10:55 ` Rasmus Villemoes
2020-10-27 12:03 ` Petr Mladek [this message]
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