X-Recipient: archive-cygwin AT delorie DOT com
DomainKey-Signature: a=rsa-sha1; c=nofws; d=sourceware.org; h=list-id
	:list-unsubscribe:list-subscribe:list-archive:list-post
	:list-help:sender:date:from:to:subject:message-id:reply-to
	:references:mime-version:content-type:in-reply-to; q=dns; s=
	default; b=ArzBM3O0NrwE5pKHERIxbBzUlv/KwjOXa4TfIuNc0LPVsY4225DWM
	FyaACn27tGAzVIcyaBGLADi9nXRg+DXVq/qQaeMUctwujRQp/NdsN3F00LrbWDTr
	5RAUbkifs90IisyVfpfeEwovW1RfjRkTe0v+d3RAe06PzQlCZVkqk8=
DKIM-Signature: v=1; a=rsa-sha1; c=relaxed; d=sourceware.org; h=list-id
	:list-unsubscribe:list-subscribe:list-archive:list-post
	:list-help:sender:date:from:to:subject:message-id:reply-to
	:references:mime-version:content-type:in-reply-to; s=default;
	 bh=AzAmnR2yagVIylAOwdWIXJ6vssM=; b=f3wRcrHVztL+hI4xK5SpwHnK1MXF
	uSeqfW2kxK/tIOFxSBAtnevBrariu48rnNB7nIyhVFgxvsn8jKUk1Soz3bFtYlfq
	efU/aZmtXnqepXRwx/yC4rbOylG7ZI8k0Z0vQsozxJDtpdzaXVUlVsefFxJWBXnF
	NYsWo5h16Ix3fLU=
Mailing-List: contact cygwin-help AT cygwin DOT com; run by ezmlm
List-Id: <cygwin.cygwin.com>
List-Subscribe: <mailto:cygwin-subscribe AT cygwin DOT com>
List-Archive: <http://sourceware.org/ml/cygwin/>
List-Post: <mailto:cygwin AT cygwin DOT com>
List-Help: <mailto:cygwin-help AT cygwin DOT com>, <http://sourceware.org/ml/#faqs>
Sender: cygwin-owner AT cygwin DOT com
Mail-Followup-To: cygwin AT cygwin DOT com
Delivered-To: mailing list cygwin AT cygwin DOT com
Authentication-Results: sourceware.org; auth=none
X-Virus-Found: No
X-Spam-SWARE-Status: No, score=-5.9 required=5.0 tests=AWL,BAYES_00 autolearn=ham version=3.3.2
X-HELO: calimero.vinschen.de
Date: Wed, 19 Feb 2014 19:46:48 +0100
From: Corinna Vinschen <corinna-cygwin AT cygwin DOT com>
To: cygwin AT cygwin DOT com
Subject: Re: Bug with dlopen() and fork()
Message-ID: <20140219184648.GW2246@calimero.vinschen.de>
Reply-To: cygwin AT cygwin DOT com
Mail-Followup-To: cygwin AT cygwin DOT com
References: <CAMzR4E63GYJPeNx27vpX5kBAFbrXDtS0k81pi5=SfKAV8fQteA AT mail DOT gmail DOT com> <CAMzR4E4jeO45W5wn4ehdwTaZ_gSKPrrEV49OjnfWwjAj3k0ZDg AT mail DOT gmail DOT com>
MIME-Version: 1.0
Content-Type: multipart/signed; micalg=pgp-sha1;	protocol="application/pgp-signature"; boundary="8MWQa5Xlpje7WrDu"
Content-Disposition: inline
In-Reply-To: <CAMzR4E4jeO45W5wn4ehdwTaZ_gSKPrrEV49OjnfWwjAj3k0ZDg@mail.gmail.com>
User-Agent: Mutt/1.5.21 (2010-09-15)

--8MWQa5Xlpje7WrDu
Content-Type: text/plain; charset=utf-8
Content-Disposition: inline
Content-Transfer-Encoding: quoted-printable

On Feb 19 14:38, Jaime Fabregas Fernandez wrote:
> Library references loaded by a process using dlopen() and dlsym() are
> no more valid in child processes after running a fork(). Calls from
> child process will never return.
>=20
> I've searched for a similar problem in the mailing lists and found
> this unanswered thread from 2001:
>=20
> http://cygwin.com/ml/cygwin/2001-02/msg01225.html
>=20
>=20
> I'm running cygwin64. This behaviour can be checked with the following
> test program:
>=20
> =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=
=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=
=3D=3D=3D=3D=3D=3D=3D
> #include <stdio.h>
> #include <dlfcn.h>
>=20
> int (*myopen)(const char *);
>=20
> main(){
>         void *handle;
>         int ret;
>         handle =3D dlopen("my_lib.dll", RTLD_LAZY);
>         myopen =3D dlsym(handle, "mylib_open");
>=20
>         if( ! fork() ){
>                 ret =3D myopen("");
>                 printf("This printf never shows, call to myopen will
> block for ever\n");
>         }
>         else{
>                 ret =3D myopen("");
>                 printf("%i\n", ret);
>                 sleep(1);
>         }
> }
> =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=
=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=
=3D=3D=3D=3D=3D=3D=3D
>=20
> Same program runs correctly (showing the two printf's) in a Linux environ=
ment.

Works for me with 64 bit Cygwin.  I used this as DLL:

  $ cat > my_lib.c <<EOF
  int
  mylib_open (const char *foo)
  {
    return 1;
  }
  $ gcc -shared -o my_lib.dll my_lib.c
  $ gcc -g -o my_tst my_tst.c		<- That's your above testcase
  $ uname -a
  CYGWIN_NT-6.3 vmbert8164 1.7.28(0.271/5/3) 2014-02-04 16:01 x86_64 Cygwin
  $ ./my_tst
  1
  This printf never shows, call to myopen will block for ever
  $


Corinna

--=20
Corinna Vinschen                  Please, send mails regarding Cygwin to
Cygwin Maintainer                 cygwin AT cygwin DOT com
Red Hat

--8MWQa5Xlpje7WrDu
Content-Type: application/pgp-signature

-----BEGIN PGP SIGNATURE-----
Version: GnuPG v1
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=ajF3
-----END PGP SIGNATURE-----

--8MWQa5Xlpje7WrDu--