From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on dcvr.yhbt.net X-Spam-Level: X-Spam-ASN: AS31976 209.132.180.0/23 X-Spam-Status: No, score=-9.1 required=3.0 tests=AWL,BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,RCVD_IN_DNSWL_HI, RP_MATCHES_RCVD shortcircuit=no autolearn=ham autolearn_force=no version=3.4.0 Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by dcvr.yhbt.net (Postfix) with ESMTP id 1AE591FEAA for ; Fri, 24 Jun 2016 22:41:55 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751305AbcFXWlw (ORCPT ); Fri, 24 Jun 2016 18:41:52 -0400 Received: from pb-smtp2.pobox.com ([64.147.108.71]:51086 "EHLO sasl.smtp.pobox.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1751019AbcFXWlw (ORCPT ); Fri, 24 Jun 2016 18:41:52 -0400 Received: from sasl.smtp.pobox.com (unknown [127.0.0.1]) by pb-smtp2.pobox.com (Postfix) with ESMTP id 98A9526D08; Fri, 24 Jun 2016 18:41:50 -0400 (EDT) DKIM-Signature: v=1; a=rsa-sha1; c=relaxed; d=pobox.com; h=from:to:cc :subject:references:date:in-reply-to:message-id:mime-version :content-type; s=sasl; bh=1Kidl4kbdSBo6HghTHH7HUcYRDM=; b=F7g69c zB2Jsn17EAGIrEsAhukLeGlnDxjtYtOW8nRCUtuTCpQzVwlieHK7mjMYqya1tgKc dxa9JSubdIXEw+n2mlN9OX29f1m3/hecAnJHrPhZaGXmD0ebZQjtCmQhcIKHbZZL s2t2wAmbxWSS8j543sg4aN/sky0GKmNDaVgc4= DomainKey-Signature: a=rsa-sha1; c=nofws; d=pobox.com; h=from:to:cc :subject:references:date:in-reply-to:message-id:mime-version :content-type; q=dns; s=sasl; b=DjY1/rgZbOb5hATbERwdi4lS3HoyaoEE 75NBnr88hziCIi1imiCjatNTyj8CN7AGXA6aIXJs9NKOhvkjs9kzuHAcslNXRTso 7pgEr9TJA36GVwljAahiO6XbA0U55glfLjzv1T+331w4SP0KGnJ4Y/ArLkRC1LNC qz6AnNO1X4Q= Received: from pb-smtp2.nyi.icgroup.com (unknown [127.0.0.1]) by pb-smtp2.pobox.com (Postfix) with ESMTP id 922A326D06; Fri, 24 Jun 2016 18:41:50 -0400 (EDT) Received: from pobox.com (unknown [104.132.0.95]) (using TLSv1.2 with cipher DHE-RSA-AES128-SHA (128/128 bits)) (No client certificate requested) by pb-smtp2.pobox.com (Postfix) with ESMTPSA id 1C2C626D04; Fri, 24 Jun 2016 18:41:50 -0400 (EDT) From: Junio C Hamano To: Jeff King Cc: git@vger.kernel.org, =?utf-8?Q?Ren=C3=A9?= Scharfe , "Robin H. Johnson" Subject: Re: [PATCH v3 1/4] t5000: test tar files that overflow ustar headers References: <20160623231512.GA27683@sigill.intra.peff.net> <20160623232041.GA3668@sigill.intra.peff.net> <20160624190744.GA32118@sigill.intra.peff.net> <20160624205858.GA23315@sigill.intra.peff.net> Date: Fri, 24 Jun 2016 15:41:47 -0700 In-Reply-To: <20160624205858.GA23315@sigill.intra.peff.net> (Jeff King's message of "Fri, 24 Jun 2016 16:58:58 -0400") Message-ID: User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/24.3 (gnu/linux) MIME-Version: 1.0 Content-Type: text/plain X-Pobox-Relay-ID: D715A616-3A5C-11E6-831A-EE617A1B28F4-77302942!pb-smtp2.pobox.com Sender: git-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: git@vger.kernel.org Jeff King writes: > The difference in time between the two is measurable on my system, but > it's only a few milliseconds (for 4096 bytes). So maybe it's not worth > worrying about (though as a general technique, it does make me worry > that it's easy to get wrong in a way that will fail racily). Yeah, GNU dd has iflag=fullblock, but if we assume GNU, we can safely assume "head -c", so I do not think of a way to do this portably enough.