From mboxrd@z Thu Jan 1 00:00:00 1970 From: Junio C Hamano Subject: Re: [PATCH 1/2] sideband.c: Use xmalloc() instead of variable-sized arrays. Date: Tue, 08 Jan 2008 12:13:13 -0800 Message-ID: <7v7iikrs86.fsf@gitster.siamese.dyndns.org> References: <4783A3B2.3060801@viscovery.net> <7v4pdotdtl.fsf@gitster.siamese.dyndns.org> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: Johannes Sixt , Git Mailing List To: Nicolas Pitre X-From: git-owner@vger.kernel.org Tue Jan 08 21:13:56 2008 Return-path: Envelope-to: gcvg-git-2@gmane.org Received: from vger.kernel.org ([209.132.176.167]) by lo.gmane.org with esmtp (Exim 4.50) id 1JCKpc-00025E-GR for gcvg-git-2@gmane.org; Tue, 08 Jan 2008 21:13:52 +0100 Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751987AbYAHUNZ (ORCPT ); Tue, 8 Jan 2008 15:13:25 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752020AbYAHUNZ (ORCPT ); Tue, 8 Jan 2008 15:13:25 -0500 Received: from a-sasl-quonix.sasl.smtp.pobox.com ([208.72.237.25]:39008 "EHLO sasl.smtp.pobox.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751746AbYAHUNY (ORCPT ); Tue, 8 Jan 2008 15:13:24 -0500 Received: from a-sasl-quonix (localhost [127.0.0.1]) by a-sasl-quonix.pobox.com (Postfix) with ESMTP id 4BED6C1E0; Tue, 8 Jan 2008 15:13:21 -0500 (EST) Received: from pobox.com (ip68-225-240-77.oc.oc.cox.net [68.225.240.77]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) by a-sasl-quonix.pobox.com (Postfix) with ESMTP id 9AC15C1DC; Tue, 8 Jan 2008 15:13:16 -0500 (EST) In-Reply-To: (Nicolas Pitre's message of "Tue, 08 Jan 2008 14:59:20 -0500 (EST)") User-Agent: Gnus/5.110006 (No Gnus v0.6) Emacs/21.4 (gnu/linux) Sender: git-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: git@vger.kernel.org Archived-At: Nicolas Pitre writes: > On Tue, 8 Jan 2008, Junio C Hamano wrote: > >> Johannes Sixt writes: >> >> > From: Johannes Sixt >> > >> > How come we got along with this not very portable construct for so long? >> > Probably because the array sizes were computed from the results of >> > strlen() of string constants. Anyway, a follow-up patch will make the >> > lengths really non-constant. >> > >> > Signed-off-by: Johannes Sixt >> > --- >> > sideband.c | 14 ++++++++++++-- >> > 1 files changed, 12 insertions(+), 2 deletions(-) >> > >> > diff --git a/sideband.c b/sideband.c >> > index 756bbc2..513d7b3 100644 >> > --- a/sideband.c >> > +++ b/sideband.c >> > @@ -19,7 +19,10 @@ int recv_sideband(const char *me, int in_stream, int out, int err) >> > { >> > unsigned pf = strlen(PREFIX); >> > unsigned sf = strlen(SUFFIX); >> > - char buf[pf + LARGE_PACKET_MAX + sf + 1]; >> > + char *buf, *save; >> > + >> > + save = xmalloc(sf); >> > + buf = xmalloc(pf + LARGE_PACKET_MAX + sf + 1); >> >> I have to wonder if the malloc() overhead is small enough >> compared to the network bandwidth to make a two malloc-free >> pairs per packet a non-issue... > > Eeek. Overhead might be insignificant, but it still doesn't feel right. > > What about using alloca() instead? This is not like if we are doing > funky things with the allocated memory anyway. That's double Eek as I recall AIX is not dead. How about using a constant large enough slop? It is not like PREFIX and SUFFIX are different vastly between calls.