From: Jakub Jelinek <jakub@redhat.com>
To: Jim Meyering <jim@meyering.net>
Cc: Janne Blomqvist <blomqvist.janne@gmail.com>,
"Joseph S. Myers" <joseph@codesourcery.com>,
gcc-patches@gcc.gnu.org, java-patches@gcc.gnu.org,
fortran@gcc.gnu.org
Subject: Re: [PATCH gcc/fortran] get rid of gfc_free
Date: Tue, 15 Mar 2011 10:08:00 -0000 [thread overview]
Message-ID: <20110315100826.GV30899@tyan-ft48-01.lab.bos.redhat.com> (raw)
In-Reply-To: <87zkow3dmp.fsf_-_@rho.meyering.net>
On Tue, Mar 15, 2011 at 11:02:38AM +0100, Jim Meyering wrote:
> > Instead of "please let us know", maybe recommend using
> > __builtin_expect instead? E.g. something like
> >
> > if (__builtin_expect (ptr != NULL, 0))
> > free (ptr);
>
> Good idea. Thanks.
> Though how about avoiding the double negative?
>
> if (__builtin_expect (ptr == NULL, 1))
> free (ptr);
What double negative? if (__builtin_expect (ptr != NULL, 0)) free (ptr);
is certainly correct, the latter is wrong, it will leak memory.
It will call free only if ptr is NULL, i.e. do a useless free (NULL),
if it is non-NULL, it will not do anything.
You could do
if (!__builtin_expect (ptr == NULL, 1))
free (ptr);
but that doesn't seem to be nicer or clearer than
if (__builtin_expect (ptr != NULL, 0))
free (ptr);
Jakub
next prev parent reply other threads:[~2011-03-15 10:08 UTC|newest]
Thread overview: 31+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <87zkp9zmq0.fsf@rho.meyering.net>
2011-03-05 19:16 ` avoid useless if-before-free tests Joseph S. Myers
2011-03-07 19:52 ` Dr Andrew John Hughes
2011-03-07 22:47 ` Joseph S. Myers
2011-03-08 16:57 ` Dr Andrew John Hughes
2011-03-08 17:07 ` Andrew Haley
2011-03-08 17:17 ` Jim Meyering
2011-03-08 10:45 ` Jim Meyering
2011-03-08 14:21 ` [PATCH v2] " Jim Meyering
2011-03-08 14:30 ` Rainer Orth
2011-03-08 15:28 ` Ian Lance Taylor
2011-03-08 15:36 ` Jakub Jelinek
2011-03-08 17:03 ` Jim Meyering
2011-03-08 18:45 ` Rainer Orth
2011-03-08 19:13 ` Jim Meyering
2011-03-08 19:20 ` Rainer Orth
2011-03-08 19:39 ` Jakub Jelinek
2011-03-08 17:54 ` [PATCH v3] " Jim Meyering
2011-03-08 19:34 ` DJ Delorie
2011-03-15 9:19 ` Janne Blomqvist
2011-03-15 10:03 ` [PATCH gcc/fortran] get rid of gfc_free Jim Meyering
2011-03-15 10:08 ` Jakub Jelinek [this message]
2011-03-15 10:27 ` Jim Meyering
2011-03-15 14:18 ` Janne Blomqvist
2011-03-15 18:21 ` Jim Meyering
2011-03-24 16:51 ` [PATCH v3] Re: avoid useless if-before-free tests Jim Meyering
2011-04-15 7:26 ` Janne Blomqvist
2011-04-15 7:54 ` Jim Meyering
2011-04-15 8:20 ` Janne Blomqvist
2011-04-15 8:23 ` Jim Meyering
2011-04-15 13:20 ` Tom Tromey
2011-04-15 17:52 ` Jim Meyering
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