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

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Message-ID: <20170522213837.GA13861@avx2>
Date:   Tue, 23 May 2017 00:38:37 +0300
From:   Alexey Dobriyan <adobriyan@...il.com>
To:     akpm@...ux-foundation.org
Cc:     linux-kernel@...r.kernel.org
Subject: [PATCH] CodingStyle: delete "kmalloc(sizeof(*var))" as preferred
 allocation form

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.