linux-kernel - Re: Make checkpatch warn about pointless casting of kalloc returns.

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Message-ID: <46C03166.1000301@shadowen.org>
Date:	Mon, 13 Aug 2007 11:24:38 +0100
From:	Andy Whitcroft <apw@...dowen.org>
To:	Dave Jones <davej@...hat.com>
CC:	jschopp <jschopp@...tin.ibm.com>, rdunlap@...otime.net,
	Linux Kernel <linux-kernel@...r.kernel.org>
Subject: Re: Make checkpatch warn about pointless casting of kalloc returns.

jschopp wrote:
>> +# check for pointless casting of kmalloc return
>> +        if ($rawline =~ /\*\)[ ]k[czm]alloc/) {
> 
> It looks to me like this will catch
> 
> foo = (char *) kmalloc(512);
> 
> but not
> 
> for = (char* )kmalloc(512);
> 
> I haven't tried it but how about something like:
> 
> if($rawline =~/\(.*\)\s*k[czm]alloc/){
> 
> which if I got it right should match the typecast with any combination
> of spacing.
> 
>> +            WARN("No need to cast return value.\n");
> 
> Could the warning be more descriptive?  This describes what, but it
> should also describe why; after all if somebody made this error they may
> not know they why.

Yes there are a few problems with the match, plus it needs to be on the
processed line to avoid false matches in strings (however unlikely).  I
ended up with the following:

                if ($line =~ /\*\s*\)\s*k[czm]alloc\b/) {
                        WARN("unnecessary cast may hide bugs, see
http://c-faq.com/malloc/mallocnocast.html\n" . $herecurr);
                }

Which just fits on the line :).

Thanks for the patch.  Will be in 0.10 coming to an -mm near you soon.

-apw
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