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Date: Thu, 20 Aug 2009 13:19:55 +0200
From: Corinna Vinschen <corinna-cygwin AT cygwin DOT com>
To: cygwin AT cygwin DOT com
Subject: Re: find(1) memory leak in cygheap
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On Aug 20 18:23, Haojun Bao wrote:
> On Thu, Aug 20, 2009 at 4:39 PM, Corinna
> Vinschen<corinna-cygwin AT cygwin DOT com> wrote:
> > On Aug 20 14:09, Haojun Bao wrote:
> >> I have done some debugging, and the culprit should be dup(2) syscall.
> >> Here's another test case, this time written in C.
> >>
> >> Note that the cygheap_start and cygheap_max value will be very likely
> >> different on your computer, so you should use gdb to take a peek into
> >> cygwin1.dll to get your value. Or else you should remove the reference
> >> to these memory location.
> >>
> >> The test case will show cygheap is always growing, and at the end it will print
> >>   1 [main] a 3560 Q:\a.exe: *** fatal error - cmalloc would have returned NULL
> >
> > Thanks for the testcase!  It was pretty easy to find the culprit with
> > it.  Deep in dup(), the strings for the filenames of the new file
> > descriptor were allocated twice.  While I was at it, I also found two
> > other potential memory leaks, which would just show up much less
> > frequent.
> >
> > This fixes your find testcase as well, and probably (hopefully?) also
> > the problem reported in http://cygwin.com/ml/cygwin/2009-08/msg00620.html
> >
> > I applied a patch to CVS and will upload a -60 release asap.
> >
> >
> > Thanks again,
> > Corinna
> >
> Great. In fact, I also found this code myself might cause problem in path.h:
> (we should test if path is NULL, and free it before the memcpy, and
> other member pointers should also be checked and free-ed first, is it
> about right?:-)

Yes and no.  It might look cleaner to free the pointers at this point
if they are non-NULL, but in fact the operator= is called after the
path_conv content has been memcpy'ed to another fhandler.  So, if you
free the pointers, you free the pointers of another file descriptor.
SEGV's galore!


Corinna

-- 
Corinna Vinschen                  Please, send mails regarding Cygwin to
Cygwin Project Co-Leader          cygwin AT cygwin DOT com
Red Hat

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