* void* arithmnetic
@ 2007-11-29 0:05 J.A. Magallón
2007-11-29 0:22 ` Arnaldo Carvalho de Melo
2007-11-29 0:39 ` Jan Engelhardt
0 siblings, 2 replies; 7+ messages in thread
From: J.A. Magallón @ 2007-11-29 0:05 UTC (permalink / raw)
To: Linux-Kernel,
Hi all...
Since begin of the ages the build of the nvidia driver says things like
this:
include/asm/compat.h:210: warning: pointer of type 'void *' used in arithmetic
There are several of this warnings. The code in question for this example
is:
static __inline__ void __user *compat_alloc_user_space(long len)
{
struct pt_regs *regs = task_pt_regs(current);
return (void __user *)regs->rsp - len;
}
As this is dealing with mem blocks, I suppose it's counting in bytes, so
we could do something like:
return (void __user *)((u8*)regs->rsp - len);
so the arithmetic knows how to inc/dec for each unity...
I think the warning is correct and that void* arithmetic is undefined in C,
isn't it ?
TIA
--
J.A. Magallon <jamagallon()ono!com> \ Software is like sex:
\ It's better when it's free
Mandriva Linux release 2008.1 (Cooker) for i586
Linux 2.6.23-jam01 (gcc 4.2.2 20070909 (4.2.2-0.RC.1mdv2008.0)) SMP PREEMPT
09 F9 11 02 9D 74 E3 5B D8 41 56 C5 63 56 88 C0
^ permalink raw reply [flat|nested] 7+ messages in thread
* Re: void* arithmnetic
2007-11-29 0:05 void* arithmnetic J.A. Magallón
@ 2007-11-29 0:22 ` Arnaldo Carvalho de Melo
2007-11-29 0:39 ` Jan Engelhardt
1 sibling, 0 replies; 7+ messages in thread
From: Arnaldo Carvalho de Melo @ 2007-11-29 0:22 UTC (permalink / raw)
To: J.A. Magallón; +Cc: linux-kernel
Em Thu, Nov 29, 2007 at 01:05:31AM +0100, J.A. Magallón escreveu:
> Hi all...
>
> Since begin of the ages the build of the nvidia driver says things like
> this:
>
> include/asm/compat.h:210: warning: pointer of type 'void *' used in arithmetic
>
> There are several of this warnings. The code in question for this example
> is:
>
> static __inline__ void __user *compat_alloc_user_space(long len)
> {
> struct pt_regs *regs = task_pt_regs(current);
> return (void __user *)regs->rsp - len;
> }
>
> As this is dealing with mem blocks, I suppose it's counting in bytes, so
> we could do something like:
>
> return (void __user *)((u8*)regs->rsp - len);
>
> so the arithmetic knows how to inc/dec for each unity...
> I think the warning is correct and that void* arithmetic is undefined in C,
> isn't it ?
Yes, but not in gcc, the language the kernel is written 8)
It is allowed and the size of a void is 1. -Wpointer-arith disables
this.
[acme@doppio ~]$ cat voidptr.c
#include <stdio.h>
int main(int argc, char *argv[])
{
void *ptr = argv[argc - 1];
puts(ptr + 4);
return 0;
}
[acme@doppio ~]$ gcc -Wall voidptr.c -o voidptr
[acme@doppio ~]$ ./a Magallón
llón
[acme@doppio ~]$ gcc -Wall -Wpointer-arith voidptr.c -o voidptr
voidptr.c: In function ‘main’:
voidptr.c:7: warning: pointer of type ‘void *’ used in arithmetic
[acme@doppio ~]$ ./a Magallón
llón
[acme@doppio ~]$
- Arnaldo
^ permalink raw reply [flat|nested] 7+ messages in thread
* Re: void* arithmnetic
2007-11-29 0:05 void* arithmnetic J.A. Magallón
2007-11-29 0:22 ` Arnaldo Carvalho de Melo
@ 2007-11-29 0:39 ` Jan Engelhardt
2007-11-29 1:19 ` Ming Lei
1 sibling, 1 reply; 7+ messages in thread
From: Jan Engelhardt @ 2007-11-29 0:39 UTC (permalink / raw)
To: J.A. Magallón; +Cc: Linux-Kernel,
On Nov 29 2007 01:05, J.A. Magallón wrote:
>
>Since begin of the ages the build of the nvidia driver says things like
>this:
>
Explicitly adding -Wpointer-arith to ones own Makefile is like
admitting the code might be problematic. :->
I think sizeof(void *) == 1 is taken as granted as sizeof(int) >= 4
these days. Sigh.
^ permalink raw reply [flat|nested] 7+ messages in thread
* Re: void* arithmnetic
2007-11-29 0:39 ` Jan Engelhardt
@ 2007-11-29 1:19 ` Ming Lei
2007-11-29 7:38 ` Benny Halevy
0 siblings, 1 reply; 7+ messages in thread
From: Ming Lei @ 2007-11-29 1:19 UTC (permalink / raw)
To: Jan Engelhardt; +Cc: J.A. Magallón, Linux-Kernel,
2007/11/29, Jan Engelhardt <jengelh@computergmbh.de>:
>
> On Nov 29 2007 01:05, J.A. Magallón wrote:
> >
> >Since begin of the ages the build of the nvidia driver says things like
> >this:
> >
>
> Explicitly adding -Wpointer-arith to ones own Makefile is like
> admitting the code might be problematic. :->
>
>
> I think sizeof(void *) == 1 is taken as granted as sizeof(int) >= 4
> these days. Sigh.
sizeof(void *) == 4, sizeof(void)==1, :)
> -
> To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
> the body of a message to majordomo@vger.kernel.org
> More majordomo info at http://vger.kernel.org/majordomo-info.html
> Please read the FAQ at http://www.tux.org/lkml/
>
^ permalink raw reply [flat|nested] 7+ messages in thread
* Re: void* arithmnetic
2007-11-29 1:19 ` Ming Lei
@ 2007-11-29 7:38 ` Benny Halevy
2007-11-29 12:31 ` WANG Cong
0 siblings, 1 reply; 7+ messages in thread
From: Benny Halevy @ 2007-11-29 7:38 UTC (permalink / raw)
To: Ming Lei; +Cc: Jan Engelhardt, "J.A. Magallón", Linux-Kernel,
On Nov. 29, 2007, 3:19 +0200, "Ming Lei" <tom.leiming@gmail.com> wrote:
> 2007/11/29, Jan Engelhardt <jengelh@computergmbh.de>:
>> On Nov 29 2007 01:05, J.A. Magallón wrote:
>>> Since begin of the ages the build of the nvidia driver says things like
>>> this:
>>>
>> Explicitly adding -Wpointer-arith to ones own Makefile is like
>> admitting the code might be problematic. :->
>>
>>
>> I think sizeof(void *) == 1 is taken as granted as sizeof(int) >= 4
>> these days. Sigh.
> sizeof(void *) == 4, sizeof(void)==1, :)
well, sizeof(void *) == sizeof(unsigned long) maybe :)
>> -
>> To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
>> the body of a message to majordomo@vger.kernel.org
>> More majordomo info at http://vger.kernel.org/majordomo-info.html
>> Please read the FAQ at http://www.tux.org/lkml/
>>
> -
> To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
> the body of a message to majordomo@vger.kernel.org
> More majordomo info at http://vger.kernel.org/majordomo-info.html
> Please read the FAQ at http://www.tux.org/lkml/
>
^ permalink raw reply [flat|nested] 7+ messages in thread
* Re: void* arithmnetic
2007-11-29 7:38 ` Benny Halevy
@ 2007-11-29 12:31 ` WANG Cong
2007-11-30 11:38 ` Geert Uytterhoeven
0 siblings, 1 reply; 7+ messages in thread
From: WANG Cong @ 2007-11-29 12:31 UTC (permalink / raw)
To: Benny Halevy
Cc: Ming Lei, Jan Engelhardt, "J.A. Magallón", Linux-Kernel,
On Thu, Nov 29, 2007 at 09:38:46AM +0200, Benny Halevy wrote:
>On Nov. 29, 2007, 3:19 +0200, "Ming Lei" <tom.leiming@gmail.com> wrote:
>> 2007/11/29, Jan Engelhardt <jengelh@computergmbh.de>:
>>> On Nov 29 2007 01:05, J.A. Magallón wrote:
>>>> Since begin of the ages the build of the nvidia driver says things like
>>>> this:
>>>>
>>> Explicitly adding -Wpointer-arith to ones own Makefile is like
>>> admitting the code might be problematic. :->
>>>
>>>
>>> I think sizeof(void *) == 1 is taken as granted as sizeof(int) >= 4
>>> these days. Sigh.
>> sizeof(void *) == 4, sizeof(void)==1, :)
>well, sizeof(void *) == sizeof(unsigned long) maybe :)
I *heard* that on Win64 sizeof(void *) > sizeof(long). But it's off-topic
here. ;-)
^ permalink raw reply [flat|nested] 7+ messages in thread
* Re: void* arithmnetic
2007-11-29 12:31 ` WANG Cong
@ 2007-11-30 11:38 ` Geert Uytterhoeven
0 siblings, 0 replies; 7+ messages in thread
From: Geert Uytterhoeven @ 2007-11-30 11:38 UTC (permalink / raw)
To: WANG Cong
Cc: Benny Halevy, Ming Lei, Jan Engelhardt,
"J.A. Magallón", Linux-Kernel,
[-- Attachment #1: Type: TEXT/PLAIN, Size: 1192 bytes --]
On Thu, 29 Nov 2007, WANG Cong wrote:
> On Thu, Nov 29, 2007 at 09:38:46AM +0200, Benny Halevy wrote:
> >On Nov. 29, 2007, 3:19 +0200, "Ming Lei" <tom.leiming@gmail.com> wrote:
> >> 2007/11/29, Jan Engelhardt <jengelh@computergmbh.de>:
> >>> On Nov 29 2007 01:05, J.A. Magallón wrote:
> >>>> Since begin of the ages the build of the nvidia driver says things like
> >>>> this:
> >>>>
> >>> Explicitly adding -Wpointer-arith to ones own Makefile is like
> >>> admitting the code might be problematic. :->
> >>>
> >>>
> >>> I think sizeof(void *) == 1 is taken as granted as sizeof(int) >= 4
> >>> these days. Sigh.
> >> sizeof(void *) == 4, sizeof(void)==1, :)
> >well, sizeof(void *) == sizeof(unsigned long) maybe :)
>
> I *heard* that on Win64 sizeof(void *) > sizeof(long). But it's off-topic
> here. ;-)
Yes, Win64 is P64, to make sure it's incompatible with the rest of the
world.
Gr{oetje,eeting}s,
Geert
--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-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
^ permalink raw reply [flat|nested] 7+ messages in thread
end of thread, other threads:[~2007-11-30 11:38 UTC | newest]
Thread overview: 7+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2007-11-29 0:05 void* arithmnetic J.A. Magallón
2007-11-29 0:22 ` Arnaldo Carvalho de Melo
2007-11-29 0:39 ` Jan Engelhardt
2007-11-29 1:19 ` Ming Lei
2007-11-29 7:38 ` Benny Halevy
2007-11-29 12:31 ` WANG Cong
2007-11-30 11:38 ` Geert Uytterhoeven
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).