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Message-ID: <1ca80eb8-c095-ad74-de29-5924a0624e1f@infradead.org>
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
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