From: Julia Lawall <julia@diku.dk> To: "Peter Hüwe" <PeterHuewe@gmx.de> Cc: Mauro Carvalho Chehab <mchehab@infradead.org>, linux-media@vger.kernel.org, linux-kernel@vger.kernel.org, kernel-janitors@vger.kernel.org, Steven Toth <stoth@kernellabs.com>, Tejun Heo <tj@kernel.org>, Dan Carpenter <error27@gmail.com> Subject: Re: [PATCH] video/saa7164: Fix sparse warning: Using plain integer as NULL pointer Date: Wed, 26 Jan 2011 06:59:39 +0100 (CET) [thread overview] Message-ID: <Pine.LNX.4.64.1101260653450.18314@ask.diku.dk> (raw) In-Reply-To: <201101252354.31217.PeterHuewe@gmx.de> [-- Attachment #1: Type: TEXT/PLAIN, Size: 1800 bytes --] On Tue, 25 Jan 2011, Peter Hüwe wrote: > Am Dienstag 25 Januar 2011, 23:20:44 schrieb Julia Lawall: > > On Tue, 25 Jan 2011, Peter Huewe wrote: > > > This patch fixes the warning "Using plain integer as NULL pointer", > > > generated by sparse, by replacing the offending 0s with NULL. > > > > I recall (a number of years ago) being told that for things like kmalloc, > > the proper test was !x, not x == NULL. > > > > julia > > > > > Hi Julia, > > thanks for your input. > So do I understand you correctly if I say > if(!x) is better than if(x==NULL) in any case? No. > Or only for the kmalloc family? > > Do you remember the reason why !x should be preferred? Because it is a function call, and NULL represents failure of that function, not an actual NULL value. Here is an email that explains that: http://lkml.org/lkml/2007/7/27/103 Here is the beginning of the thread: http://lkml.org/lkml/2007/7/27/75 julia > In Documentation/CodingStyle , Chapter 7: Centralized exiting of functions > there is a function fun with looks like this: > int fun(int a) > { > int result = 0; > char *buffer = kmalloc(SIZE); > > if (buffer == NULL) > return -ENOMEM; > > if (condition1) { > while (loop1) { > ... > } > result = 1; > goto out; > } > ... > out: > kfree(buffer); > return result; > } > > > --> So if (buffer == NULL) is in the official CodingStyle - maybe we should > add a paragraph there as well ;) > > > Don't get me wrong, I just want to learn ;) > > > Thanks, > Peter > > -- > To unsubscribe from this list: send the line "unsubscribe kernel-janitors" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html >
WARNING: multiple messages have this Message-ID (diff)
From: Julia Lawall <julia@diku.dk> To: "Peter Hüwe" <PeterHuewe@gmx.de> Cc: Mauro Carvalho Chehab <mchehab@infradead.org>, linux-media@vger.kernel.org, linux-kernel@vger.kernel.org, kernel-janitors@vger.kernel.org, Steven Toth <stoth@kernellabs.com>, Tejun Heo <tj@kernel.org>, Dan Carpenter <error27@gmail.com> Subject: Re: [PATCH] video/saa7164: Fix sparse warning: Using plain integer Date: Wed, 26 Jan 2011 05:59:39 +0000 [thread overview] Message-ID: <Pine.LNX.4.64.1101260653450.18314@ask.diku.dk> (raw) In-Reply-To: <201101252354.31217.PeterHuewe@gmx.de> [-- Attachment #1: Type: TEXT/PLAIN, Size: 1877 bytes --] On Tue, 25 Jan 2011, Peter Hüwe wrote: > Am Dienstag 25 Januar 2011, 23:20:44 schrieb Julia Lawall: > > On Tue, 25 Jan 2011, Peter Huewe wrote: > > > This patch fixes the warning "Using plain integer as NULL pointer", > > > generated by sparse, by replacing the offending 0s with NULL. > > > > I recall (a number of years ago) being told that for things like kmalloc, > > the proper test was !x, not x == NULL. > > > > julia > > > > > Hi Julia, > > thanks for your input. > So do I understand you correctly if I say > if(!x) is better than if(x==NULL) in any case? No. > Or only for the kmalloc family? > > Do you remember the reason why !x should be preferred? Because it is a function call, and NULL represents failure of that function, not an actual NULL value. Here is an email that explains that: http://lkml.org/lkml/2007/7/27/103 Here is the beginning of the thread: http://lkml.org/lkml/2007/7/27/75 julia > In Documentation/CodingStyle , Chapter 7: Centralized exiting of functions > there is a function fun with looks like this: > int fun(int a) > { > int result = 0; > char *buffer = kmalloc(SIZE); > > if (buffer == NULL) > return -ENOMEM; > > if (condition1) { > while (loop1) { > ... > } > result = 1; > goto out; > } > ... > out: > kfree(buffer); > return result; > } > > > --> So if (buffer == NULL) is in the official CodingStyle - maybe we should > add a paragraph there as well ;) > > > Don't get me wrong, I just want to learn ;) > > > Thanks, > Peter > > -- > To unsubscribe from this list: send the line "unsubscribe kernel-janitors" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html >
next prev parent reply other threads:[~2011-01-26 5:59 UTC|newest] Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top 2011-01-25 20:54 [PATCH] video/saa7164: Fix sparse warning: Using plain integer as NULL pointer Peter Huewe 2011-01-25 20:54 ` Peter Huewe 2011-01-25 22:20 ` Julia Lawall 2011-01-25 22:20 ` [PATCH] video/saa7164: Fix sparse warning: Using plain integer Julia Lawall 2011-01-25 22:54 ` [PATCH] video/saa7164: Fix sparse warning: Using plain integer as NULL pointer Peter Hüwe 2011-01-25 22:54 ` Peter Hüwe 2011-01-25 23:05 ` Devin Heitmueller 2011-01-25 23:05 ` [PATCH] video/saa7164: Fix sparse warning: Using plain integer as Devin Heitmueller 2011-01-26 0:30 ` [PATCH] video/saa7164: Fix sparse warning: Using plain integer as NULL pointer Andy Walls 2011-01-26 0:30 ` [PATCH] video/saa7164: Fix sparse warning: Using plain integer Andy Walls 2011-01-26 5:59 ` Julia Lawall [this message] 2011-01-26 5:59 ` Julia Lawall 2011-01-26 9:29 ` [PATCH] video/saa7164: Fix sparse warning: Using plain integer as NULL pointer Mauro Carvalho Chehab 2011-01-26 9:29 ` [PATCH] video/saa7164: Fix sparse warning: Using plain integer Mauro Carvalho Chehab 2011-01-30 19:33 ` [PATCH v2] video/saa7164: Fix sparse warning: Using plain integer as NULL pointer Peter Huewe 2011-01-30 19:33 ` Peter Huewe 2011-01-30 20:02 ` Devin Heitmueller 2011-01-30 20:02 ` [PATCH v2] video/saa7164: Fix sparse warning: Using plain integer Devin Heitmueller 2011-01-26 4:25 ` [PATCH] video/saa7164: Fix sparse warning: Using plain integer as NULL pointer Dan Carpenter 2011-01-26 4:25 ` [PATCH] video/saa7164: Fix sparse warning: Using plain integer Dan Carpenter
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