From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jeff King Subject: Re: [PATCH 4/4] transport: drop "int cmp = cmp" hack Date: Mon, 25 Mar 2013 17:06:25 -0400 Message-ID: <20130325210625.GA16386@sigill.intra.peff.net> References: <20130321110338.GA18552@sigill.intra.peff.net> <20130321111333.GD18819@sigill.intra.peff.net> <20130324093212.GA28234@sigill.intra.peff.net> <7vfvzjxnq9.fsf@alter.siamese.dyndns.org> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Cc: git@vger.kernel.org To: Junio C Hamano X-From: git-owner@vger.kernel.org Mon Mar 25 22:06:59 2013 Return-path: Envelope-to: gcvg-git-2@plane.gmane.org Received: from vger.kernel.org ([209.132.180.67]) by plane.gmane.org with esmtp (Exim 4.69) (envelope-from ) id 1UKEbZ-0007Dd-TA for gcvg-git-2@plane.gmane.org; Mon, 25 Mar 2013 22:06:58 +0100 Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758671Ab3CYVG3 (ORCPT ); Mon, 25 Mar 2013 17:06:29 -0400 Received: from 75-15-5-89.uvs.iplsin.sbcglobal.net ([75.15.5.89]:39395 "EHLO peff.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751600Ab3CYVG2 (ORCPT ); Mon, 25 Mar 2013 17:06:28 -0400 Received: (qmail 28357 invoked by uid 107); 25 Mar 2013 21:08:14 -0000 Received: from sigill.intra.peff.net (HELO sigill.intra.peff.net) (10.0.0.7) (smtp-auth username relayok, mechanism cram-md5) by peff.net (qpsmtpd/0.84) with ESMTPA; Mon, 25 Mar 2013 17:08:14 -0400 Received: by sigill.intra.peff.net (sSMTP sendmail emulation); Mon, 25 Mar 2013 17:06:25 -0400 Content-Disposition: inline In-Reply-To: <7vfvzjxnq9.fsf@alter.siamese.dyndns.org> Sender: git-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: git@vger.kernel.org Archived-At: On Mon, Mar 25, 2013 at 12:50:54PM -0700, Junio C Hamano wrote: > >> transport.c: In function 'get_refs_via_rsync': > >> transport.c:127:29: error: 'cmp' may be used uninitialized in this > >> function [-Werror=uninitialized] > >> transport.c:109:7: note: 'cmp' was declared here > >> > >> gcc (Ubuntu/Linaro 4.6.3-1ubuntu5) 4.6.3 > > > > Right, that's the same version I noted above. Is 4.6.3 the default > > compiler under a particular release of Ubuntu, or did you use their > > gcc-4.6 package? > > I'll check later with one of my VMs. The copy of U 12.04 I happened > to have handy has that version installed. Ah, if you didn't explicitly run "gcc-4.6", then it was probably the default version in 12.04 (as it was for a while in Debian testing, but they never actually made a release with it, so everybody is now on 4.7 by default). > By the way, I find this piece of code less than pleasant: > > * It uses "struct ref dummy = { NULL }, *tail = &dummy", and then > accumulates things by appending to "&tail" and then returns > dummy.next. Why doesn't it do > > struct ref *retval = NULL, **tail = &retval; > > and pass tail around to append things, like everybody else? Is > this another instance of "People do not understand linked list" > problem? Perhaps fixing that may unconfuse the compiler? Ugh, that is horrible. At first I thought it was even wrong, as we pass &tail and not &dummy.next to read_loose_refs. But two wrongs _do_ make a right, because read_loose_refs, rather than do: *tail = new; tail = &new->next; does: (*tail)->next = new; *tail = new; > Later, the tail of the same list is passed to insert_packed_refs(), > which does in-place merging of this list and the contents of the > packed_refs file. These two data sources have to be sorted the > same way for this merge to work correctly, but there is no > validating the order of the entries it reads from the packed-refs > file. At least, it should barf when the file is not sorted. It > could be lenient and accept a mal-sorted input, but I do not think > that is advisable. Actually, it is the head of the loose list (though it is hard to realize, because it is called tail!). > I'll apply the attached on 'maint' for now, as rsync is not worth > spending too many cycles on worrying about; I need to go to the > bathroom to wash my eyes after staring this code for 20 minutes X-<. Yeah, it's quite ugly. I really wonder if it is time to drop rsync support. I'd be really surprised if anybody is actively using it. I wonder, though, what made you look at this. It did not come up in my list of -Wuninitialized warnings. Did it get triggered by one of the other gcc versions? > diff --git a/transport.c b/transport.c > index 87b8f14..e6f9346 100644 > --- a/transport.c > +++ b/transport.c > @@ -106,7 +106,8 @@ static void insert_packed_refs(const char *packed_refs, struct ref **list) > return; > > for (;;) { > - int cmp, len; > + int cmp = 0; /* assigned before used */ > + int len; > > if (!fgets(buffer, sizeof(buffer), f)) { > fclose(f); I think that's fine. -Peff