Re: Lots of new warnings with gcc-7.1.1

From: Linus Torvalds <torvalds@linux-foundation.org>
To: Guenter Roeck <linux@roeck-us.net>
Cc: "linux-fbdev@vger.kernel.org" <linux-fbdev@vger.kernel.org>,
	Jean Delvare <jdelvare@suse.com>,
	"James E.J. Bottomley" <jejb@linux.vnet.ibm.com>,
	Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com>,
	Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	Sathya Prakash <sathya.prakash@broadcom.com>,
	the arch/x86 maintainers <x86@kernel.org>,
	linux-block <linux-block@vger.kernel.org>,
	IDE-ML <linux-ide@vger.kernel.org>,
	Network Development <netdev@vger.kernel.org>,
	Tejun Heo <tj@kernel.org>,
	xen-devel <xen-devel@lists.xenproject.org>,
	Linux Media Mailing List <linux-media@vger.kernel.org>
Subject: Re: Lots of new warnings with gcc-7.1.1
Date: Tue, 11 Jul 2017 20:41:09 -0700	[thread overview]
Message-ID: <CA+55aFx5mCk+nzDG+gGzDUqE4gzJVERL_oO+PN-PA6oKaUhCpg__24428.7612069913$1499830936$gmane$org@mail.gmail.com> (raw)
In-Reply-To: <CA+55aFyKpezj3oHwtBShyf9x-DJNAGQhrq55iVGM42eWKQtP3w@mail.gmail.com>

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On Tue, Jul 11, 2017 at 8:17 PM, Linus Torvalds
<torvalds@linux-foundation.org> wrote:
>
> If that's the case, I'd prefer just turning off the format-truncation
> (but not overflow) warning with '-Wno-format-trunction".

Doing

 KBUILD_CFLAGS  += $(call cc-disable-warning, format-truncation)

in the main Makefile certainly cuts down on the warnings.

We still have some overflow warnings, including the crazy one where
gcc doesn't see that the number of max7315 boards is very limited.

But those could easily be converted to just snprintf() instead, and
then the truncation warning disabling takes care of it. Maybe that's
the right answer.

We also have about a bazillion

    warning: ‘*’ in boolean context, suggest ‘&&’ instead

warnings in drivers/ata/libata-core.c, all due to a single macro that
uses a pattern that gcc-7.1.1 doesn't like. The warning looks a bit
debatable, but I suspect the macro could easily be changed too.

Tejun, would you hate just moving the "multiply by 1000" part _into_
that EZ() macro? Something like the attached (UNTESTED!) patch?

              Linus

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 drivers/ata/libata-core.c | 20 ++++++++++----------
 1 file changed, 10 insertions(+), 10 deletions(-)

diff --git a/drivers/ata/libata-core.c b/drivers/ata/libata-core.c
index 8453f9a4682f..4c7d5a138495 100644
--- a/drivers/ata/libata-core.c
+++ b/drivers/ata/libata-core.c
@@ -3231,19 +3231,19 @@ static const struct ata_timing ata_timing[] = {
 };
 
 #define ENOUGH(v, unit)		(((v)-1)/(unit)+1)
-#define EZ(v, unit)		((v)?ENOUGH(v, unit):0)
+#define EZ(v, unit)		((v)?ENOUGH((v)*1000, unit):0)
 
 static void ata_timing_quantize(const struct ata_timing *t, struct ata_timing *q, int T, int UT)
 {
-	q->setup	= EZ(t->setup      * 1000,  T);
-	q->act8b	= EZ(t->act8b      * 1000,  T);
-	q->rec8b	= EZ(t->rec8b      * 1000,  T);
-	q->cyc8b	= EZ(t->cyc8b      * 1000,  T);
-	q->active	= EZ(t->active     * 1000,  T);
-	q->recover	= EZ(t->recover    * 1000,  T);
-	q->dmack_hold	= EZ(t->dmack_hold * 1000,  T);
-	q->cycle	= EZ(t->cycle      * 1000,  T);
-	q->udma		= EZ(t->udma       * 1000, UT);
+	q->setup	= EZ(t->setup,      T);
+	q->act8b	= EZ(t->act8b,      T);
+	q->rec8b	= EZ(t->rec8b,      T);
+	q->cyc8b	= EZ(t->cyc8b,      T);
+	q->active	= EZ(t->active,     T);
+	q->recover	= EZ(t->recover,    T);
+	q->dmack_hold	= EZ(t->dmack_hold, T);
+	q->cycle	= EZ(t->cycle,      T);
+	q->udma		= EZ(t->udma,       UT);
 }
 
 void ata_timing_merge(const struct ata_timing *a, const struct ata_timing *b,

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