linux-kernel - Re: [PATCH] ath9k: remove useless if-before-kfree; correct misleading indentation

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Date:	Sat, 23 Aug 2008 13:28:51 +0200
From:	Jim Meyering <jim@...ering.net>
To:	Marcel Holtmann <holtmann@...ux.intel.com>
Cc:	linux-kernel@...r.kernel.org, Sujith.Manoharan@...eros.com,
	linville@...driver.com
Subject: Re: [PATCH] ath9k: remove useless if-before-kfree; correct misleading indentation

Marcel Holtmann <holtmann@...ux.intel.com> wrote:
>> >> Alternatively, you could remove the nowadays-useless
>> >> "if-before-kfree" test and leave the sometimes-redundant
>> >> assignment as-is: unconditional.
>> >
>> > actually the later one is preferred. Just remove the NULL check.
>>
>> I prefer it, too, but the indentation suggested that
>> adding braces would match the author's intent.
>>
>> In case anyone is interested, I have been maintaining a patch
>> that removes *all* useless if-before-kfree tests.  I have not
>> posted it because such changes have a reputation for provoking
>> flames on this list, but now you've provoked me ;-)
>>
>>     http://meyering.net/code/remove-useless-if-before-kfree.patch
>>      74 files changed, 127 insertions(+), 250 deletions(-)
>
> I am all for this patch.
>
> Even the Glibc free() function will do an "if-before-free" :)

Hi Marcel,

Thanks for the support.

Yes, with glibc, free(NULL) is a no-op, and POSIX has required that
behavior for long enough that *all* implementations of free on reasonable
porting targets are NULL-safe these days.  There has been plenty of
discussion as I've helped a few projects clean up in this regard, e.g.,

  http://thread.gmane.org/gmane.comp.version-control.git/74187
  http://thread.gmane.org/gmane.emacs.devel/98144
  http://thread.gmane.org/gmane.comp.lib.gnulib.bugs/12712

Here are most of the projects that have endured this janitorial work:
    git
    emacs
    glibc
    gnulib
    coreutils
    freeIPA
    libvirt
    util-linux-ng
    idutils

There's even a tool to help ensure that no new useless if-before-kfree
tests sneak back in later.

    http://git.sv.gnu.org/gitweb/?p=gnulib.git;a=blob_plain;f=build-aux/useless-if-before-free
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