From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([208.118.235.92]:36657) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1TPG3r-0002qr-VA for qemu-devel@nongnu.org; Fri, 19 Oct 2012 13:08:44 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1TPG3q-0007e2-21 for qemu-devel@nongnu.org; Fri, 19 Oct 2012 13:08:39 -0400 Received: from mx1.redhat.com ([209.132.183.28]:23485) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1TPG3p-0007dr-OS for qemu-devel@nongnu.org; Fri, 19 Oct 2012 13:08:37 -0400 Message-ID: <50818909.50102@redhat.com> Date: Fri, 19 Oct 2012 11:08:25 -0600 From: Eric Blake MIME-Version: 1.0 References: <1350391578-1191-1-git-send-email-alex@alex.org.uk> <507EC493.2090308@redhat.com> <508183E0.3000106@redhat.com> In-Reply-To: <508183E0.3000106@redhat.com> Content-Type: multipart/signed; micalg=pgp-sha256; protocol="application/pgp-signature"; boundary="------------enig430FF80C1370D917E4BB97A3" Subject: Re: [Qemu-devel] [PATCHv4] qemu-img rebase: use empty string to rebase without backing file List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Kevin Wolf Cc: qemu-devel@nongnu.org, Alex Bligh This is an OpenPGP/MIME signed message (RFC 2440 and 3156) --------------enig430FF80C1370D917E4BB97A3 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: quoted-printable On 10/19/2012 10:46 AM, Kevin Wolf wrote: >> As it happens, we despite what Eric Blake said, we couldn't get an uns= afe >> rebase to no backing file to work with the existing code (with our wit= hout >> our patch). The second option may fix this bug. Reading line 1497, is = this >> because the semantic is not 'an empty string', but 'omit -b entirely'?= >> This behaviour is undocumented in the manpage which specifies -b as a >> compulsory option. If so, that's a bit unfortunate as we now have diff= erent >> semantics with and without -u. Note if no -b parameter is supplied, th= ere >> is also a possible null pointer exception at line 1693 (null passed to= >> error_report). >=20 > Right. I think not passing -b at all or passing an empty string should > have the same meaning, namely removing the backing file reference. I > won't try to modify this patch to do this, though, we can do it on top.= Agreed - a future patch that makes -b optional rather than mandatory, where '-b ""' and omitting the argument have the same semantics whether or not -u is present, would be nice. --=20 Eric Blake eblake@redhat.com +1-919-301-3266 Libvirt virtualization library http://libvirt.org --------------enig430FF80C1370D917E4BB97A3 Content-Type: application/pgp-signature; name="signature.asc" Content-Description: OpenPGP digital signature Content-Disposition: attachment; filename="signature.asc" -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.12 (GNU/Linux) Comment: Public key at http://people.redhat.com/eblake/eblake.gpg Comment: Using GnuPG with Mozilla - http://www.enigmail.net/ iQEcBAEBCAAGBQJQgYkKAAoJEKeha0olJ0NqXnIH/3TbOT++uO4TzzuekjDigXXf Flnyl0/vWKbNlHL1aznLndCW+nnjdEUqZXn6Lv9/C9tAAEouUQncrKfiA7ek/u88 bST3nSSNKF9OVcqZLfbbDgUe5iqMO4AKwolhVfQcFokMbfA6j4i2fAKK/sqr0eAt lZbszD1iF3iLgPP/5oy/yepxRZslTvycl+ly8EFhZe/ZQz8+N8e/msaIqvLBq8gj zhpZZuCA5sPB8c5eo+fLeURiQ9j899ZQ704Kba4o5owTQZpXPRA8QQTdDXA+CmoT FjeC1xltthNVBzgUzgpTDfdYDFUuPuuyHRLxoZZ7GI1DgjoRp5iOzAP/oZks4DQ= =wdi0 -----END PGP SIGNATURE----- --------------enig430FF80C1370D917E4BB97A3--