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SubjectRe: [PATCH] CodingStyle: delete "kmalloc(sizeof(*var))" as preferred allocation form
On Mon, 22 May 2017 14:43:18 -0700 Joe Perches <joe@perches.com> 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@gmail.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.

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!

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