From mboxrd@z Thu Jan 1 00:00:00 1970 From: Ramsay Jones Subject: Re: [PATCH] bisect: save heap memory. allocate only the required amount Date: Tue, 26 Aug 2014 13:59:52 +0100 Message-ID: <53FC84C8.1020300@ramsay1.demon.co.uk> References: <1408889844-5407-1-git-send-email-arjun024@gmail.com> <53FA0054.5060808@gmail.com> <20140825130732.GD17288@peff.net> <20140826110303.GA25736@peff.net> <53FC7621.7090102@ramsay1.demon.co.uk> <20140826121359.GA29180@peff.net> <53FC7F98.5070204@ramsay1.demon.co.uk> <20140826124344.GF29180@peff.net> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit Cc: Junio C Hamano , Stefan Beller , Arjun Sreedharan , Git Mailing List , Christian Couder , =?UTF-8?B?Tmd1eeG7hW4gVGjDoWk=?= =?UTF-8?B?IE5n4buNYyBEdXk=?= To: Jeff King X-From: git-owner@vger.kernel.org Tue Aug 26 15:00:11 2014 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 1XMGM4-0006TT-H7 for gcvg-git-2@plane.gmane.org; Tue, 26 Aug 2014 15:00:08 +0200 Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758023AbaHZM77 (ORCPT ); Tue, 26 Aug 2014 08:59:59 -0400 Received: from mdfmta004.mxout.tch.inty.net ([91.221.169.45]:39309 "EHLO smtp.demon.co.uk" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1755091AbaHZM75 (ORCPT ); Tue, 26 Aug 2014 08:59:57 -0400 Received: from mdfmta004.tch.inty.net (unknown [127.0.0.1]) by mdfmta004.tch.inty.net (Postfix) with ESMTP id 5094FAC40BE; Tue, 26 Aug 2014 13:59:55 +0100 (BST) Received: from mdfmta004.tch.inty.net (unknown [127.0.0.1]) by mdfmta004.tch.inty.net (Postfix) with ESMTP id 0AACDAC40B7; Tue, 26 Aug 2014 13:59:55 +0100 (BST) Received: from [10.0.2.15] (unknown [80.176.147.220]) (using TLSv1 with cipher DHE-RSA-AES128-SHA (128/128 bits)) (No client certificate requested) by mdfmta004.tch.inty.net (Postfix) with ESMTP; Tue, 26 Aug 2014 13:59:54 +0100 (BST) User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:31.0) Gecko/20100101 Thunderbird/31.0 In-Reply-To: <20140826124344.GF29180@peff.net> X-MDF-HostID: 17 Sender: git-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: git@vger.kernel.org Archived-At: On 26/08/14 13:43, Jeff King wrote: > On Tue, Aug 26, 2014 at 01:37:44PM +0100, Ramsay Jones wrote: > >>> On my 64-bit system using gcc, sizeof() returns 16; it has to pad the >>> whole thing to 64-bit alignment in case I put two of them in an array. >>> But offsetof(name) is 12, since the array of char does not need the same >>> alignment; it can go right after the type and make use of the padding >>> bits. >> >> Hmm, interesting. I must re-read the standard. I was convinced that the >> standard *requires* any alignment padding to come *before* the name field. >> (how would you put a, non-trivial, variable data structure into an array?) > > I think you don't. How would you compute a[1] if a[0] has a variable > size? > > You can put a flex-array structure into an array, but then each element > has the flex member as zero-size (and you should not access it, of > course). Exactly. ;-) ATB, Ramsay Jones