&array[0] vs array

&array[0] vs array

[Tobin C. Harding]

Does the kernel community have a preference when using the address of
the first element of an an array?

1. addr = &array[0]
2. addr = array;

$ grep '\&.*\[0\]' | wc -l
10077

style (1) is clearly used, I was not able to grep for instances where
style (2) is used.

thanks,
Tobin.

&array[0] vs array

[Ruben Safir]

On 03/29/2017 08:30 PM, Tobin C. Harding wrote:
> Does the kernel community have a preference when using the address of
> the first element of an an array?
> 
> 1. addr = &array[0]
> 2. addr = array;
> 
> $ grep '\&.*\[0\]' | wc -l
> 10077
> 
> style (1) is clearly used, I was not able to grep for instances where
> style (2) is used.

maybe there is a another reason why 2 is not used.

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&array[0] vs array

[Nicholas Mc Guire]

On Thu, Mar 30, 2017 at 09:04:35AM -0400, Ruben Safir wrote:
> On 03/29/2017 08:30 PM, Tobin C. Harding wrote:
> > Does the kernel community have a preference when using the address of
> > the first element of an an array?
> > 
> > 1. addr = &array[0]
> > 2. addr = array;
> > 
> > $ grep '\&.*\[0\]' | wc -l
> > 10077
> > 
> > style (1) is clearly used, I was not able to grep for instances where
> > style (2) is used.
> 
> maybe there is a another reason why 2 is not used.
>
the second form is used - just not quite as often  
with the below quick (and probably incomplete) coccinelle script you 
can find a few hundred occurences of the second form in linux-next 

<snip>
virtual report

@v2@
identifier array,addr;
type T;
position p;
@@

(
* T array[];
|
* T array[] = ...;
)
 ...
* addr = array at p
 
@script:python@
p << v2.p;
@@
print "%s:%s" % (p[0].file,p[0].line)
<snip>

If its really obvious that its an array that you are manipulating
maybe the second version is fine - if its not so obvious the
first version makes it clear - and as readability is a key issue
for any complex code I suspect that readability explains the preference.

thx!
hofrat

&array[0] vs array

[Tobin C. Harding]

On Thu, Mar 30, 2017 at 04:05:51PM +0000, Nicholas Mc Guire wrote:
> On Thu, Mar 30, 2017 at 09:04:35AM -0400, Ruben Safir wrote:
> > On 03/29/2017 08:30 PM, Tobin C. Harding wrote:
> > > Does the kernel community have a preference when using the address of
> > > the first element of an an array?
> > > 
> > > 1. addr = &array[0]
> > > 2. addr = array;
> > > 
> > > $ grep '\&.*\[0\]' | wc -l
> > > 10077
> > > 
> > > style (1) is clearly used, I was not able to grep for instances where
> > > style (2) is used.
> > 
> > maybe there is a another reason why 2 is not used.
> >
> the second form is used - just not quite as often  
> with the below quick (and probably incomplete) coccinelle script you 
> can find a few hundred occurences of the second form in linux-next 
> 
> <snip>
> virtual report
> 
> @v2@
> identifier array,addr;
> type T;
> position p;
> @@
> 
> (
> * T array[];
> |
> * T array[] = ...;
> )
>  ...
> * addr = array at p
>  
> @script:python@
> p << v2.p;
> @@
> print "%s:%s" % (p[0].file,p[0].line)
> <snip>
> 
> If its really obvious that its an array that you are manipulating
> maybe the second version is fine - if its not so obvious the
> first version makes it clear - and as readability is a key issue
> for any complex code I suspect that readability explains the preference.

Got it, readability over brevity.

thanks,
Tobin.