linux-kernel - Re: coccinelle: generalized removal of unnecessary pointer casts?

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Message-ID: <alpine.DEB.2.02.1603142136490.2040@localhost6.localdomain6>
Date:	Mon, 14 Mar 2016 21:43:48 +0100 (CET)
From:	Julia Lawall <julia.lawall@...6.fr>
To:	Joe Perches <joe@...ches.com>
cc:	cocci <cocci@...teme.lip6.fr>, LKML <linux-kernel@...r.kernel.org>,
	Dan Carpenter <error27@...il.com>,
	kernel-janitors <kernel-janitors@...r.kernel.org>
Subject: Re: coccinelle: generalized removal of unnecessary pointer casts?



On Mon, 14 Mar 2016, Joe Perches wrote:

> I wrote a little cocci script to remove unnecessary
> casts for memset and memcpy (below) and tested it on
> linux kernel's drivers/staging/ directory.
> 
> For instance, when dst and src are already pointers:
> 
> -	memcpy((u8 *)dst, (u8 *)src, r8712_get_wlan_bssid_ex_sz(src));
> +	memcpy(dst, src, r8712_get_wlan_bssid_ex_sz(src));
> 
> It works ok, (it doesn't remove unnecessary parentheses
> around the pointers) but it makes me wonder if there's a
> generalized spatch mechanism to remove casts when an
> arbitrary function takes a void * in any argument
> position and a call to that function uses a cast of a
> pointer to any pointer type for that argument.
> 
> $ cat remove_mem_casts.cocci 
> @@
> type t;
> t *p;
> type v;
> expression e1;
> expression e2;
> @@
> 
> -	memset((v*)p, e1, e2)
> +	memset(p, e1, e2)
> 
> @@
> type t;
> t *p;
> type v;
> expression e1;
> expression e2;
> @@
> 
> -	memcpy((v*)p, e1, e2)
> +	memcpy(p, e1, e2)
> 
> @@
> type t;
> t *p;
> type v;
> expression e1;
> expression e2;
> @@
> 
> -	memcpy(e1, (v*)p, e2)
> +	memcpy(e1, p, e2)
> 
> @@
> type t1;
> type t2;
> t1 *p1;
> t2 *p2;
> type v1;
> type v2;
> expression e1;
> @@
> 
> -	memcpy((v1*)p1, (v2*)p2, e1)
> +	memcpy(p1, p2, e1)

This should do everything:

@@
identifier f;
expression *e;
type T;
@@

f(...,
- (T *)(
  e
- )
  ,...)

@@
identifier f;
expression *e;
type T;
@@

f(...,
- (T *)
  e
  ,...)

julia