linux-kernel - Re: [PATCH] CodingStyle: delete "kmalloc(sizeof(*var))" as preferred allocation form

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Date:   Mon, 22 May 2017 14:49:16 -0700
From:   Randy Dunlap <rdunlap@...radead.org>
To:     Joe Perches <joe@...ches.com>,
        Alexey Dobriyan <adobriyan@...il.com>,
        akpm@...ux-foundation.org
Cc:     linux-kernel@...r.kernel.org
Subject: Re: [PATCH] CodingStyle: delete "kmalloc(sizeof(*var))" as preferred
 allocation form

On 05/22/17 14:43, Joe Perches wrote:
> On Tue, 2017-05-23 at 00:38 +0300, Alexey Dobriyan wrote:
>> There are valid reasons for
>>
>> 	malloc(sizeof(struct S))
>>
>> form:
>>
>> * struct S acts as an anchor for ctags quickly reminding which type is
>>   in focus
>>
>> * argument re changing name prevents bugs is semi bogus:
>>   such changes are rare,
>>   "void *" cast gives both forms equal opportunity to be screwed up
>>
>> * proper way to fix those rare misallocation bugs (which indeed happened)
>>   is type safe allocation macros (see tmalloc from Samba).
>>
>>   However amount of disruption will be so high so it may never be done.
>>
>> * ratio of allocation styles is ~6400:12000 which is about 1:2
>>   so the amount of churn to maintain this rule is pretty high in theory.
>>
>> The winning move is to not play and not encourage people send trivial stuff.
>>
>> Signed-off-by: Alexey Dobriyan <adobriyan@...il.com>
>> ---
>>
>>  Documentation/process/coding-style.rst |   10 ----------
>>  1 file changed, 10 deletions(-)
>>
>> --- a/Documentation/process/coding-style.rst
>> +++ b/Documentation/process/coding-style.rst
>> @@ -808,16 +808,6 @@ kmalloc(), kzalloc(), kmalloc_array(), kcalloc(), vmalloc(), and
>>  vzalloc().  Please refer to the API documentation for further information
>>  about them.
>>  
>> -The preferred form for passing a size of a struct is the following:
>> -
>> -.. code-block:: c
>> -
>> -	p = kmalloc(sizeof(*p), ...);
>> -
>> -The alternative form where struct name is spelled out hurts readability and
>> -introduces an opportunity for a bug when the pointer variable type is changed
>> -but the corresponding sizeof that is passed to a memory allocator is not.
>> -
>>  Casting the return value which is a void pointer is redundant. The conversion
>>  from void pointer to any other pointer type is guaranteed by the C programming
>>  language.
> 
> Thanks.  I agree with this deletion.
> 

Acked-by: Randy Dunlap <rdunlap@...radead.org>

Thanks.


-- 
~Randy