linux-kernel - Re: [PATCH] HID: roccat: Drop cast

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Date:	Sun, 29 Jun 2014 18:34:14 +0200 (CEST)
From:	Julia Lawall <julia.lawall@...6.fr>
To:	Joe Perches <joe@...ches.com>
cc:	Himangi Saraogi <himangi774@...il.com>,
	Stefan Achatz <erazor_de@...rs.sourceforge.net>,
	Jiri Kosina <jkosina@...e.cz>, linux-input@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] HID: roccat: Drop cast



On Thu, 26 Jun 2014, Joe Perches wrote:

> On Fri, 2014-06-27 at 07:29 +0200, Julia Lawall wrote:
> > On Thu, 26 Jun 2014, Joe Perches wrote:
> > > The cast of a const void * to a void * was odd.
> > > 
> > > Maybe a mechanism to verify appropriateness of
> > > loss of constness for any pointer might be useful.
> > 
> > I tried the following, but didn't find anything interesting:
> > 
> > @disable drop_cast@
> > type T;
> > const T e;
> > @@
> > 
> > * (T)e
> 
> What code does this match?
> Do you have an example match?
> 
> This doesn't find a cast of a void type like:
> 
> void func(const void * const p)
> {
> 	char *p2 = p;
> 
> 	p2[0] = 1;
> }

Is this a real example?  Because gcc complains about this sort of problem.  
I made a semantic patch that detects this, but since gcc does the same 
thing, it doesn't seem very interesting.  Coccinelle gives a few false 
positives due to lack of type information.

julia
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