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

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Date:   Mon, 22 May 2017 15:41:42 -0700
From:   Joe Perches <joe@...ches.com>
To:     Andrew Morton <akpm@...ux-foundation.org>
Cc:     Alexey Dobriyan <adobriyan@...il.com>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] CodingStyle: delete "kmalloc(sizeof(*var))" as
 preferred allocation form

On Mon, 2017-05-22 at 15:22 -0700, Andrew Morton wrote:
> On Mon, 22 May 2017 14:43:18 -0700 Joe Perches <joe@...ches.com> wrote:
> > On Tue, 2017-05-23 at 00:38 +0300, Alexey Dobriyan wrote:
> > > * 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.

I got:

$ git grep -E "alloc.*\bsizeof\s*\(\s*[^\*]" | wc -l
8114
$ git grep -E "alloc.*\bsizeof\s*\(\s*[\*]" | wc -l
12198

> > > -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.
> > > -
> > 
> > Thanks.  I agree with this deletion.
> 
> I don't.  Every damn time I see a p = kmalloc(sizeof struct foo) I have
> to hunt around to check the type of p.  And I review a lot of code!

Yeah, I read a lot of patches with you.
But there are real reasons to use sizeof(type) too.
And changing existing uses is pretty pointless.