linux-kernel - Re: [PATCH] Fix pointer cast for 32 bits arch

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Date:	Mon, 13 Apr 2015 13:25:15 +0200
From:	Peter Senna Tschudin <peter.senna@...il.com>
To:	Geert Uytterhoeven <geert@...ux-m68k.org>
Cc:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Loic Pefferkorn <loic@...cp.eu>, Alan <alan@...ux.intel.com>,
	Jun Tian <jun.j.tian@...el.com>,
	Octavian Purdila <octavian.purdila@...el.com>,
	Garret Kelly <garret.kelly@...il.com>,
	Kristina Martšenko <kristina.martsenko@...il.com>,
	Nick Kralevich <nnk@...gle.com>,
	driverdevel <devel@...verdev.osuosl.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] Fix pointer cast for 32 bits arch

Line 4677 of http://pastebin.com/2bi9Dg7k looks like a bug

diff -u -p a/arch/powerpc/kernel/signal_32.c b/arch/powerpc/kernel/signal_32.c
-       regs->nip = (unsigned long) (unsigned long)ksig->ka.sa.sa_handler;

On Mon, Apr 13, 2015 at 1:21 PM, Geert Uytterhoeven
<geert@...ux-m68k.org> wrote:
> Hi Peter,
>
> On Mon, Apr 13, 2015 at 1:14 PM, Peter Senna Tschudin
> <peter.senna@...il.com> wrote:
>>> Perhaps checkpatch should complain about casts outside header files?
>> Cocinelle found 664 double casts:
>> http://pastebin.com/2bi9Dg7k
>>
>> and 9 triple casts:
>> http://pastebin.com/RkJhPTTV
>
> I think double casts are only needed when casting between integers
> and pointers of different sizes:
>   1. One cast to make the sizes match,
>   2. One cast to convert between pointer and integer.
>
> I think triple casts can always be simplified.
> Or am I missing some use cases?
>
>> Those are 'not' patches, just the output of Coccinelle for analysis.
>> The .cocci for triple cast:
>> @@
>> expression e1, e2;
>> type t1, t2, t3;
>> @@
>> e1 =
>> - (t1)(t2)(t3)
>> e2
>>
>> So if there are cast patterns known to be wrong, it is easy to find
>> and probably fix them with Coccinelle.
>
> It depends on the original type and on the destination type.
>
> Gr{oetje,eeting}s,
>
>                         Geert
>
> --
> Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@...ux-m68k.org
>
> In personal conversations with technical people, I call myself a hacker. But
> when I'm talking to journalists I just say "programmer" or something like that.
>                                 -- Linus Torvalds



-- 
Peter
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