linux-kernel - Re: [PATCH] printf: fix Woverride-init warning for EDEADLK errno

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Date:   Tue, 27 Oct 2020 10:12:18 +0100
From:   Petr Mladek <pmladek@...e.com>
To:     Arnd Bergmann <arnd@...nel.org>
Cc:     Rasmus Villemoes <linux@...musvillemoes.dk>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Uwe Kleine-König <uwe@...ine-koenig.org>,
        Andy Shevchenko <andy.shevchenko@...il.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] printf: fix Woverride-init warning for EDEADLK errno

On Tue 2020-10-27 09:46:28, Arnd Bergmann wrote:
> On Tue, Oct 27, 2020 at 8:23 AM Rasmus Villemoes
> <linux@...musvillemoes.dk> wrote:
> > On 26/10/2020 22.49, Arnd Bergmann wrote:
> > > From: Arnd Bergmann <arnd@...db.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 :-)

And we should remove the ECANCELLED definition. It is always the same
as ECANCELED and replaced. We do not define EWOULDBLOCK and
EREFUSED either.

Best Regards,
Petr