From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail191.messagelabs.com (mail191.messagelabs.com [216.82.242.19]) by kanga.kvack.org (Postfix) with ESMTP id 6AA0B900086 for ; Fri, 15 Apr 2011 12:32:54 -0400 (EDT) Date: Fri, 15 Apr 2011 19:28:24 +0300 From: Phil Carmody Subject: Re: [PATCH 0/1] mm: make read-only accessors take const pointer parameters Message-ID: <20110415162824.GF7112@esdhcp04044.research.nokia.com> References: <1302861377-8048-1-git-send-email-ext-phil.2.carmody@nokia.com> <20110415145133.GO15707@random.random> <20110415155916.GD7112@esdhcp04044.research.nokia.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: Sender: owner-linux-mm@kvack.org List-ID: To: ext Michal Nazarewicz Cc: ext Andrea Arcangeli , akpm@linux-foundation.org, cl@linux-foundation.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org On 15/04/11 18:12 +0200, ext Michal Nazarewicz wrote: > On Fri, 15 Apr 2011 17:59:16 +0200, Phil Carmody wrote: >> I'm just glad this wasn't an insta-nack, as I am quite a fan of >> consts, and hopefully something can be worked out. > > I feel you man. Unfortunately, I think that const, since it's an > after-thought, is not very usable in C. > > For instance, as you've pointed in your patch, the "_ro" suffix > is sort of dumb, but without it compound_head would have to take > const and return non-const (like strchr() does) which is kinda > stupid as well. > > What's more, because of lack of encapsulation, a??const struct pagea?? > only means that the object is const but thighs it points to aren't. > As such, const does not really play that well with structs anyway. I'm very glad you've mentioned that point, I forgot to. I've taken the view that in the absense of inside knowledge, const should be inherited down all pointers. So not only will I not change you, but I will not change anything you point to. No hidden side effects of any kind. That reduces where it can be used, but is a much stronger statement when it can be made. > const is, in my opinion, one of those things C++ actually got > right (or close to right). I shouldn't be seen to agree with you on that, lest any fellow Nokians notice that I've implied something positive about C++ after my rant on our core chat channel a few days back. ;-) Cheers, Phil -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/ Don't email: email@kvack.org