Date: Mon, 17 Oct 2005 13:53:11 -0400 From: John Baldwin <jhb@freebsd.org> To: freebsd-doc@freebsd.org Cc: freebsd-gnats-submit@freebsd.org, David Leppik <dleppik@vocalabs.com> Subject: Re: docs/87548: LIST_*, TAILQ_* man pages include memory leak in sample code Message-ID: <200510171353.12772.jhb@freebsd.org> In-Reply-To: <200510162150.j9GLoCAt040327@www.freebsd.org> References: <200510162150.j9GLoCAt040327@www.freebsd.org>
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On Sunday 16 October 2005 05:50 pm, David Leppik wrote:
> >Number: 87548
> >Category: docs
> >Synopsis: LIST_*, TAILQ_* man pages include memory leak in sample
> > code Confidential: no
> >Severity: non-critical
> >Priority: low
> >Responsible: freebsd-doc
> >State: open
> >Quarter:
> >Keywords:
> >Date-Required:
> >Class: doc-bug
> >Submitter-Id: current-users
> >Arrival-Date: Sun Oct 16 22:00:27 GMT 2005
> >Closed-Date:
> >Last-Modified:
> >Originator: David Leppik
> >Release: None (old BSD code--see below)
> >Organization:
>
> Vocal Laboratories
>
> >Environment:
> >Description:
>
> I've seen this on Mac OS X and Linux, so this probably affects FreeBSD as
> well.
>
> The man page for TAILQ_INSERT, TAILQ_REMOVE, etc. have the following sample
> code:
>
> while (head.tqh_first != NULL)
> TAILQ_REMOVE(&head, head.tqh_first, entries);
>
> I was so shocked that I checked queue.h and sure enough, TAILQ_REMOVE does
> not deallocate the queue entry (nor should it.) The same is true for the
> other structures mentioned in this man page.
>
> >How-To-Repeat:
> >
> >Fix:
>
> I'm just a lowly Java programmer, but I think the fix is:
>
> while (head.tqh_first != NULL) {
> np = head.tqh_first;
> TAILQ_REMOVE(&head, np, entries);
> free(np);
> }
>
Well, it should be something like:
while (!TAILQ_EMPTY(&head)) {
np = TAILQ_FIRST(&head);
TAILQ_REMOVE(&head, np, entries);
free(np);
}
And actually, on my machine here running current this is what the examples
look like:
/* TailQ Deletion. */
while (!TAILQ_EMPTY(&head)) {
n1 = TAILQ_FIRST(&head);
TAILQ_REMOVE(&head, n1, entries);
free(n1);
}
/* Faster TailQ Deletion. */
n1 = TAILQ_FIRST(&head);
while (n1 != NULL) {
n2 = TAILQ_NEXT(n1, entries);
free(n1);
n1 = n2;
}
TAILQ_INIT(&head);
Which version of FreeBSD are you seeing the memory leak in?
--
John Baldwin <jhb@FreeBSD.org> <>< http://www.FreeBSD.org/~jhb/
"Power Users Use the Power to Serve" = http://www.FreeBSD.org
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