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

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Message-ID: <CAMuHMdWrPpqqhmF+0PQwNtKObYPa94J7FuoSrE-Uysy08goV4g@mail.gmail.com>
Date:	Mon, 13 Apr 2015 13:21:40 +0200
From:	Geert Uytterhoeven <geert@...ux-m68k.org>
To:	Peter Senna Tschudin <peter.senna@...il.com>
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

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
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