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From: David Daney <ddaney@caviumnetworks.com>
To: Geert Uytterhoeven <geert@linux-m68k.org>
Cc: Michael Buesch <mb@bu3sch.de>,
	linuxppc-dev@lists.ozlabs.org, torvalds@linux-foundation.org,
	akpm@linux-foundation.org, linux-mips@linux-mips.org,
	Heiko Carstens <heiko.carstens@de.ibm.com>,
	linuxppc-dev@ozlabs.org, Paul Mackerras <paulus@samba.org>,
	"H. Peter Anvin" <hpa@zytor.com>,
	linux-s390@vger.kernel.org, linux-am33-list@redhat.com,
	Helge Deller <deller@gmx.de>,
	x86@kernel.org, Ingo Molnar <mingo@redhat.com>,
	Mike Frysinger <vapier@gentoo.org>,
	Ivan Kokshaysky <ink@jurassic.park.msu.ru>,
	uclinux-dist-devel@blackfin.uclinux.org,
	Thomas Gleixner <tglx@linutronix.de>,
	Richard Henderson <rth@twiddle.net>,
	Haavard Skinnemoen <hskinnemoen@atmel.com>,
	linux-parisc@vger.kernel.org, linux-kernel@vger.kernel.org,
	ralf@linux-mips.org, Kyle McMartin <kyle@mcmartin.ca>,
	linux-alpha@vger.kernel.org,
	Martin Schwidefsky <schwidefsky@de.ibm.com>,
	linux390@de.ibm.com, Koichi Y
Subject: Re: [PATCH 01/10] Add support for GCC-4.5's __builtin_unreachable() to compiler.h
Date: Mon, 14 Sep 2009 08:40:23 -0700	[thread overview]
Message-ID: <4AAE63E7.90909@caviumnetworks.com> (raw)
In-Reply-To: <10f740e80909120022m72ad5ea7t692fba93cd3114e9@mail.gmail.com>

Geert Uytterhoeven wrote:
> On Fri, Sep 11, 2009 at 17:58, David Daney<ddaney@caviumnetworks.com> wrote:
>> Michael Buesch wrote:
>>> On Friday 11 September 2009 01:56:42 David Daney wrote:
>>>> +/* Unreachable code */
>>>> +#ifndef unreachable
>>>> +# define unreachable() do { for (;;) ; } while (0)
>>>> +#endif
>>> # define unreachable() do { } while (1)
>>>
>>> ? :)
>> Clearly I was not thinking clearly when I wrote that part.  RTH noted the
>> same thing.  I will fix it.
> 
> However, people are so used to seeing the `do { } while (0)' idiom,
> that they might miss
> there's a `1' here, not a `0'.
> 
> So perhaps it's better to use plain `for (;;)' for infinite loops?
> 

I don't think so.  The only valid token that can follow 'do { } while 
(1)' is ';', any statement may follow 'for (;;)', so there is a greater 
possibility to silently screw things up with the for(;;) form.

David Daney


WARNING: multiple messages have this Message-ID (diff)
From: David Daney <ddaney@caviumnetworks.com>
To: Geert Uytterhoeven <geert@linux-m68k.org>
Cc: Michael Buesch <mb@bu3sch.de>,
	linuxppc-dev@lists.ozlabs.org, torvalds@linux-foundation.org,
	akpm@linux-foundation.org, linux-mips@linux-mips.org,
	Heiko Carstens <heiko.carstens@de.ibm.com>,
	linuxppc-dev@ozlabs.org, Paul Mackerras <paulus@samba.org>,
	"H. Peter Anvin" <hpa@zytor.com>,
	linux-s390@vger.kernel.org, linux-am33-list@redhat.com,
	Helge Deller <deller@gmx.de>,
	x86@kernel.org, Ingo Molnar <mingo@redhat.com>,
	Mike Frysinger <vapier@gentoo.org>,
	Ivan Kokshaysky <ink@jurassic.park.msu.ru>,
	uclinux-dist-devel@blackfin.uclinux.org,
	Thomas Gleixner <tglx@linutronix.de>,
	Richard Henderson <rth@twiddle.net>,
	Haavard Skinnemoen <hskinnemoen@atmel.com>,
	linux-parisc@vger.kernel.org, linux-kernel@vger.kernel.org,
	ralf@linux-mips.org, Kyle McMartin <kyle@mcmartin.ca>,
	linux-alpha@vger.kernel.org,
	Martin Schwidefsky <schwidefsky@de.ibm.com>,
	linux390@de.ibm.com,
	Koichi Yasutake <yasutake.koichi@jp.panasonic.com>
Subject: Re: [PATCH 01/10] Add support for GCC-4.5's __builtin_unreachable() to compiler.h
Date: Mon, 14 Sep 2009 08:40:23 -0700	[thread overview]
Message-ID: <4AAE63E7.90909@caviumnetworks.com> (raw)
In-Reply-To: <10f740e80909120022m72ad5ea7t692fba93cd3114e9@mail.gmail.com>

Geert Uytterhoeven wrote:
> On Fri, Sep 11, 2009 at 17:58, David Daney<ddaney@caviumnetworks.com> wrote:
>> Michael Buesch wrote:
>>> On Friday 11 September 2009 01:56:42 David Daney wrote:
>>>> +/* Unreachable code */
>>>> +#ifndef unreachable
>>>> +# define unreachable() do { for (;;) ; } while (0)
>>>> +#endif
>>> # define unreachable() do { } while (1)
>>>
>>> ? :)
>> Clearly I was not thinking clearly when I wrote that part.  RTH noted the
>> same thing.  I will fix it.
> 
> However, people are so used to seeing the `do { } while (0)' idiom,
> that they might miss
> there's a `1' here, not a `0'.
> 
> So perhaps it's better to use plain `for (;;)' for infinite loops?
> 

I don't think so.  The only valid token that can follow 'do { } while 
(1)' is ';', any statement may follow 'for (;;)', so there is a greater 
possibility to silently screw things up with the for(;;) form.

David Daney


WARNING: multiple messages have this Message-ID (diff)
From: David Daney <ddaney@caviumnetworks.com>
To: Geert Uytterhoeven <geert@linux-m68k.org>
Cc: Michael Buesch <mb@bu3sch.de>,
	linuxppc-dev@lists.ozlabs.org, torvalds@linux-foundation.org,
	akpm@linux-foundation.org, linux-mips@linux-mips.org,
	Heiko Carstens <heiko.carstens@de.ibm.com>,
	linuxppc-dev@ozlabs.org, Paul Mackerras <paulus@samba.org>,
	"H. Peter Anvin" <hpa@zytor.com>,
	linux-s390@vger.kernel.org, linux-am33-list@redhat.com,
	Helge Deller <deller@gmx.de>,
	x86@kernel.org, Ingo Molnar <mingo@redhat.com>,
	Mike Frysinger <vapier@gentoo.org>,
	Ivan Kokshaysky <ink@jurassic.park.msu.ru>,
	uclinux-dist-devel@blackfin.uclinux.org,
	Thomas Gleixner <tglx@linutronix.de>,
	Richard Henderson <rth@twiddle.net>,
	Haavard Skinnemoen <hskinnemoen@atmel.com>,
	linux-parisc@vger.kernel.org, linux-kernel@vger.kernel.org,
	ralf@linux-mips.org, Kyle McMartin <kyle@mcmartin.ca>,
	linux-alpha@vger.kernel.org,
	Martin Schwidefsky <schwidefsky@de.ibm.com>,
	linux390@de.ibm.com, Koichi
Subject: Re: [PATCH 01/10] Add support for GCC-4.5's __builtin_unreachable() to compiler.h
Date: Mon, 14 Sep 2009 08:40:23 -0700	[thread overview]
Message-ID: <4AAE63E7.90909@caviumnetworks.com> (raw)
In-Reply-To: <10f740e80909120022m72ad5ea7t692fba93cd3114e9@mail.gmail.com>

Geert Uytterhoeven wrote:
> On Fri, Sep 11, 2009 at 17:58, David Daney<ddaney@caviumnetworks.com> wrote:
>> Michael Buesch wrote:
>>> On Friday 11 September 2009 01:56:42 David Daney wrote:
>>>> +/* Unreachable code */
>>>> +#ifndef unreachable
>>>> +# define unreachable() do { for (;;) ; } while (0)
>>>> +#endif
>>> # define unreachable() do { } while (1)
>>>
>>> ? :)
>> Clearly I was not thinking clearly when I wrote that part.  RTH noted the
>> same thing.  I will fix it.
> 
> However, people are so used to seeing the `do { } while (0)' idiom,
> that they might miss
> there's a `1' here, not a `0'.
> 
> So perhaps it's better to use plain `for (;;)' for infinite loops?
> 

I don't think so.  The only valid token that can follow 'do { } while 
(1)' is ';', any statement may follow 'for (;;)', so there is a greater 
possibility to silently screw things up with the for(;;) form.

David Daney

WARNING: multiple messages have this Message-ID (diff)
From: David Daney <ddaney@caviumnetworks.com>
To: Geert Uytterhoeven <geert@linux-m68k.org>
Cc: linux-mips@linux-mips.org,
	Heiko Carstens <heiko.carstens@de.ibm.com>,
	linuxppc-dev@ozlabs.org, Paul Mackerras <paulus@samba.org>,
	"H. Peter Anvin" <hpa@zytor.com>,
	linux-s390@vger.kernel.org, linux-am33-list@redhat.com,
	Helge Deller <deller@gmx.de>,
	x86@kernel.org, Ingo Molnar <mingo@redhat.com>,
	Mike Frysinger <vapier@gentoo.org>,
	Ivan Kokshaysky <ink@jurassic.park.msu.ru>,
	linux390@de.ibm.com, Thomas Gleixner <tglx@linutronix.de>,
	Richard Henderson <rth@twiddle.net>,
	Haavard Skinnemoen <hskinnemoen@atmel.com>,
	linux-parisc@vger.kernel.org, torvalds@linux-foundation.org,
	linux-kernel@vger.kernel.org, ralf@linux-mips.org,
	Kyle McMartin <kyle@mcmartin.ca>,
	linux-alpha@vger.kernel.org,
	Martin Schwidefsky <schwidefsky@de.ibm.com>,
	uclinux-dist-devel@blackfin.uclinux.org,
	akpm@linux-foundation.org,
	Koichi Yasutake <yasutake.koichi@jp.panasonic.com>,
	linuxppc-dev@lists.ozlabs.org
Subject: Re: [PATCH 01/10] Add support for GCC-4.5's __builtin_unreachable() to compiler.h
Date: Mon, 14 Sep 2009 08:40:23 -0700	[thread overview]
Message-ID: <4AAE63E7.90909@caviumnetworks.com> (raw)
In-Reply-To: <10f740e80909120022m72ad5ea7t692fba93cd3114e9@mail.gmail.com>

Geert Uytterhoeven wrote:
> On Fri, Sep 11, 2009 at 17:58, David Daney<ddaney@caviumnetworks.com> wrote:
>> Michael Buesch wrote:
>>> On Friday 11 September 2009 01:56:42 David Daney wrote:
>>>> +/* Unreachable code */
>>>> +#ifndef unreachable
>>>> +# define unreachable() do { for (;;) ; } while (0)
>>>> +#endif
>>> # define unreachable() do { } while (1)
>>>
>>> ? :)
>> Clearly I was not thinking clearly when I wrote that part.  RTH noted the
>> same thing.  I will fix it.
> 
> However, people are so used to seeing the `do { } while (0)' idiom,
> that they might miss
> there's a `1' here, not a `0'.
> 
> So perhaps it's better to use plain `for (;;)' for infinite loops?
> 

I don't think so.  The only valid token that can follow 'do { } while 
(1)' is ';', any statement may follow 'for (;;)', so there is a greater 
possibility to silently screw things up with the for(;;) form.

David Daney

  reply	other threads:[~2009-09-14 15:40 UTC|newest]

Thread overview: 50+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2009-09-10 23:54 [PATCH 00/10] Add support for GCC's __builtin_unreachable() and use it in BUG David Daney
2009-09-10 23:54 ` David Daney
2009-09-10 23:56 ` [PATCH 01/10] Add support for GCC-4.5's __builtin_unreachable() to compiler.h David Daney
2009-09-10 23:56   ` David Daney
2009-09-10 23:56   ` David Daney
2009-09-10 23:56   ` David Daney
2009-09-11  0:14   ` Richard Henderson
2009-09-11  0:14     ` Richard Henderson
2009-09-11  0:14     ` Richard Henderson
2009-09-11 14:32   ` Michael Buesch
2009-09-11 14:32     ` Michael Buesch
2009-09-11 14:32     ` Michael Buesch
2009-09-11 15:58     ` David Daney
2009-09-11 15:58       ` David Daney
2009-09-11 15:58       ` David Daney
2009-09-11 15:58       ` David Daney
2009-09-12  7:22       ` Geert Uytterhoeven
2009-09-12  7:22         ` Geert Uytterhoeven
2009-09-12  7:22         ` Geert Uytterhoeven
2009-09-12  7:22         ` Geert Uytterhoeven
2009-09-12  7:22         ` Geert Uytterhoeven
2009-09-12  7:22         ` Geert Uytterhoeven
2009-09-14 15:40         ` David Daney [this message]
2009-09-14 15:40           ` David Daney
2009-09-14 15:40           ` David Daney
2009-09-14 15:40           ` David Daney
2009-09-10 23:56 ` [PATCH 02/10] x86: Convert BUG() to use unreachable() David Daney
2009-09-11  0:56   ` H. Peter Anvin
2009-09-11  1:09     ` Roland McGrath
2009-09-11  1:13     ` Linus Torvalds
2009-09-11  1:33       ` H. Peter Anvin
2009-09-11  1:37       ` Roland McGrath
2009-09-11  1:42         ` H. Peter Anvin
2009-09-11  6:07       ` Ingo Molnar
2009-09-11 15:55         ` David Daney
2009-09-13 20:12           ` H. Peter Anvin
2009-09-10 23:56 ` [PATCH 03/10] MIPS: " David Daney
2009-09-10 23:56 ` [PATCH 04/10] s390: " David Daney
2009-09-11 12:18   ` Martin Schwidefsky
2009-09-11 12:18     ` Martin Schwidefsky
2009-09-10 23:56 ` [PATCH 05/10] mn10300: " David Daney
2009-09-10 23:56 ` [PATCH 06/10] parisc: " David Daney
2009-09-28  3:20   ` Kyle McMartin
2009-09-10 23:56 ` [PATCH 07/10] powerpc: " David Daney
2009-09-10 23:56   ` David Daney
2009-09-10 23:56 ` [PATCH 08/10] alpha: " David Daney
2009-09-10 23:56 ` [PATCH 09/10] avr32: " David Daney
2009-09-11  7:31   ` Haavard Skinnemoen
2009-09-10 23:56 ` [PATCH 10/10] blackfin: " David Daney
2009-09-24  3:37 ` [PATCH 00/10] Add support for GCC's __builtin_unreachable() and use it in BUG Benjamin Herrenschmidt

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