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Date: Tue, 10 Dec 2002 17:36:45 +0100
From: Corinna Vinschen <corinna-cygwin AT cygwin DOT com>
To: cygwin AT cygwin DOT com
Subject: Re: cygwin 1.3.17-1 gethostbyname() leak
Message-ID: <20021210173645.D26891@cygbert.vinschen.de>
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References: <01a001c2a029$0d9950d0$3492fea9 AT NOELG> <Pine DOT GSO DOT 4 DOT 44 DOT 0212101024110 DOT 12239-100000 AT slinky DOT cs DOT nyu DOT edu>
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On Tue, Dec 10, 2002 at 10:36:04AM -0500, Igor Pechtchanski wrote:
> On Tue, 10 Dec 2002, Noel Gordon wrote:
> 
> > Anyone else confirm that the following program compiled under
> > gcc 3.2, cygwin 1.3.17-1, on Win2k leaks memory?

Confirmed.  I found the missing free().

> >From http://www.opengroup.org/onlinepubs/007904975/functions/gethostbyaddr.html :
> 
>       The gethostbyaddr() and gethostbyname() functions *may* return
>       pointers to static data, which may be overwritten by subsequent
>       calls to any of these functions.
> 
> The "may" above (emphasis is mine) means that the implementation is free
> to malloc a data structure and require the user to free it.  Since you
> don't free the returned data structure in your program, it's quite
> possible that there's a leak.  Also, Cygwin uses the gethostbyname from
> wsock32.dll, which may have different implementations on different
> systems.  Thus, your best bet is to look up gethostbyname on MSDN for
> implementation details.

Ignore MSDN.  It's using an internal per-thread buffer which collides with
the fork/exec mechanism of Cygwin so Cygwin duplicates the buffer to
another Cygwin-thread specific allocated buffer.  The deallocation of
the buffer is Cygwin internal so hands off please.

Thanks for the report, I've checked in a patch,
Corinna

-- 
Corinna Vinschen                  Please, send mails regarding Cygwin to
Cygwin Developer                                mailto:cygwin AT cygwin DOT com
Red Hat, Inc.

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