linux-kernel - Re: [PATCH] ARC: build: Turn off -Wmaybe-uninitialized for ARC gcc 4.8

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Date:	Fri, 18 Mar 2016 16:13:28 +0530
From:	Vineet Gupta <Vineet.Gupta1@...opsys.com>
To:	Arnd Bergmann <arnd@...db.de>
CC:	<linux-snps-arc@...ts.infradead.org>,
	Claudiu Zissulescu <Claudiu.Zissulescu@...opsys.com>,
	Michal Marek <mmarek@...e.cz>,
	"Geert Uytterhoeven" <geert@...ux-m68k.org>,
	<linux-kbuild@...r.kernel.org>, <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] ARC: build: Turn off -Wmaybe-uninitialized for ARC gcc
 4.8

On Friday 18 March 2016 03:59 PM, Arnd Bergmann wrote:
> On Friday 18 March 2016 15:50:11 Vineet Gupta wrote:
>> Sure, but I prefer this to be only for gcc 4.8 as this warning seems to be
>> healthy in small doses  At least it keeps the door open for future discussion
>> with gcc guys !
> 
> FWIW, testing on ARM with gcc-6.0 -O3, I also get tons of maybe-uninitialized
> warnings. It's unlikely that this is architecture specific or fixed in newer
> compiler versions.

So we disable this for good just like -Os.
What a shame - seemed like a reasonable safety net for programming errors.

>> The following nested construct actually works - does that look OK to you ?
>>
>> ARCH_CFLAGS += -O3 $(call cc-ifversion, -lt, 0408, $(call cc-disable-warning,maybe-uninitialized,))
> 
> Yes, that seems ok.

There was typo actually -lt needed to be -eq

> I don't really understand why -O3 is needed though, maybe it's better to
> assume that it won't be needed in future gcc versions and do

Not sure what you mean, -O3 for triggering the warnings or -O3 in ARC makefile at all.
Assuming it's latter, this is how its been forever and was added consciously as
performance seemed better with -O3 than the default -O2.


> 
> ARCH_CFLAGS += $(call cc-ifversion, -lt, 0408, -O3 $(call cc-disable-warning,maybe-uninitialized,))
> 
> 	Arnd
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