linux-kernel - Re: idio{,ma}tic typos (was Re: + fix-vm_can_nonlinear-check-in-sys_remap_file

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Date:	Thu, 11 Oct 2007 09:27:21 -0700
From:	Josh Triplett <josh@...edesktop.org>
To:	Alexey Dobriyan <adobriyan@...ru>
CC:	Al Viro <viro@....linux.org.uk>, linux-kernel@...r.kernel.org,
	davej@...emonkey.org.uk, Pierre Ossman <drzeus@...eus.cx>,
	akpm@...l.org, linux-sparse@...r.kernel.org
Subject: Re: idio{,ma}tic typos (was Re: + fix-vm_can_nonlinear-check-in-sys_remap_file_pages.patch
 added to -mm tree)

Alexey Dobriyan wrote:
> On Wed, Oct 10, 2007 at 04:45:46AM -0700, Josh Triplett wrote:
>> Alexey Dobriyan wrote:
>>> ["if (!x & y)" patch from yanzheng@]
>>> ["if (!x & y)" patch from adobriyan@]
>>> ["if (!x & y)" patches from viro@]
>>>
>>> While we're at it, below is somewhat ugly sparse patch for detecting
>>> "&& 0x" typos.
>> Excellent idea!  I think it applies to || as well.
> 
> Sadly, yes.
> 
> [PATCH] smctr: fix "|| 0x" typo
> 
> IBM_PASS_SOURCE_ADDR is 1, so logically ORing it with status bits is
> pretty useless. Do bitwise OR, instead.
> 
> Signed-off-by: Alexey Dobriyan <adobriyan@...ru>
> ---
> 
>  drivers/net/tokenring/smctr.c |    2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> --- a/drivers/net/tokenring/smctr.c
> +++ b/drivers/net/tokenring/smctr.c
> @@ -3413,7 +3413,7 @@ static int smctr_make_tx_status_code(struct net_device *dev,
>          tsv->svi = TRANSMIT_STATUS_CODE;
>          tsv->svl = S_TRANSMIT_STATUS_CODE;
>  
> -        tsv->svv[0] = ((tx_fstatus & 0x0100 >> 6) || IBM_PASS_SOURCE_ADDR);
> +        tsv->svv[0] = ((tx_fstatus & 0x0100 >> 6) | IBM_PASS_SOURCE_ADDR);
>  
>          /* Stripped frame status of Transmitted Frame */
>          tsv->svv[1] = tx_fstatus & 0xff;

Nice catch.  I agree with Kyle, though, that fixing it may require
some care to make sure it doesn't break things relying on the bug.

>> I'll most likely
>> add a -Wboolean-logic-on-bit-constant to turn this warning on.
> 
> Ewww, more options. :-(

With heuristic warnings like this, people need a way to turn them off.

>> Any reason why this wouldn't apply to octal constants or to GCC's new
>> binary constants?  I can trivially modify this patch to handle those
>> as well, just by dropping the check for an 'x' or 'X', and renaming the
>> flag.
> 
> OK, let me try too.

Go for it.  I look forward to your next patch.

Thanks,
Josh Triplett
-
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