From owner-svn-src-head@freebsd.org Fri May 5 16:32:35 2017 Return-Path: Delivered-To: svn-src-head@mailman.ysv.freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:1900:2254:206a::19:1]) by mailman.ysv.freebsd.org (Postfix) with ESMTP id C9980D5FC0B; Fri, 5 May 2017 16:32:35 +0000 (UTC) (envelope-from brde@optusnet.com.au) Received: from mail108.syd.optusnet.com.au (mail108.syd.optusnet.com.au [211.29.132.59]) by mx1.freebsd.org (Postfix) with ESMTP id 8F3D51135; Fri, 5 May 2017 16:32:34 +0000 (UTC) (envelope-from brde@optusnet.com.au) Received: from besplex.bde.org (c122-106-153-191.carlnfd1.nsw.optusnet.com.au [122.106.153.191]) by mail108.syd.optusnet.com.au (Postfix) with ESMTPS id 8E4E21A73DB; Sat, 6 May 2017 02:32:25 +1000 (AEST) Date: Sat, 6 May 2017 02:32:22 +1000 (EST) From: Bruce Evans X-X-Sender: bde@besplex.bde.org To: Ed Maste cc: Konstantin Belousov , Bruce Evans , "src-committers@freebsd.org" , "svn-src-all@freebsd.org" , "svn-src-head@freebsd.org" Subject: Re: svn commit: r317809 - head/share/man/man7 In-Reply-To: Message-ID: <20170506020904.P2496@besplex.bde.org> References: <201705042131.v44LVokb076951@repo.freebsd.org> <20170505174957.B875@besplex.bde.org> <20170505094601.GW1622@kib.kiev.ua> <20170505222702.Y1875@besplex.bde.org> <20170505143147.GX1622@kib.kiev.ua> MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII; format=flowed X-Optus-CM-Score: 0 X-Optus-CM-Analysis: v=2.2 cv=VbSHBBh9 c=1 sm=1 tr=0 a=Tj3pCpwHnMupdyZSltBt7Q==:117 a=Tj3pCpwHnMupdyZSltBt7Q==:17 a=kj9zAlcOel0A:10 a=pGLkceISAAAA:8 a=OpMgnD7Atq4i_23W64QA:9 a=G7YTQpE6ddUxrw_3:21 a=GkVXHrhHzGPYDDt4:21 a=CjuIK1q_8ugA:10 a=6kGIvZw6iX1k4Y-7sg4_:22 X-BeenThere: svn-src-head@freebsd.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: SVN commit messages for the src tree for head/-current List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Fri, 05 May 2017 16:32:35 -0000 On Fri, 5 May 2017, Ed Maste wrote: > On 5 May 2017 at 10:31, Konstantin Belousov wrote: >> On Fri, May 05, 2017 at 11:39:23PM +1000, Bruce Evans wrote: >>> >>> Change "size" to "representation" if you want to allow for more than the >>> size changing. >> I suggest you to negotiate a formulation with brooks@, who provided the >> existing note. > > If it's really undesirable to mention pointer integrity here, I think > the main point can still be made with a phrase like Bruce proposed > (but I think it's fine as it exists now). No one except Cheri developers would know the Cheri meaning of "integrity mechanism". "Representation" is a general term that is fuzzy enough to work here. The representation can be almost anything, so using this term reduces the statement to a warning that it should not be assumed that pointers have the same [binary] representation as unsigned long, although the previous paragraph says that they [currently] do. > What about "In order to maximize compatibility with future changes in > pointer size or representation, manipulation..."? Or just remove the statement that pointers have the same representation as unsigned long, so that FreeBSD gurantees nothing more than the C standard for pointers, or emphasize this. > Very briefly (to give some context), in CheriBSD and the CHERI CPU > pointers are 128 or 256 bits wide, and have a base address, length, > permissions, and other fields. Thus the size differs from existing > standard integer types, and a pointer's representation and even the > essence of what a pointer is differs from pointers in existing FreeBSD > architectures. How does it restore the extra information when converting back from intptr_t? Bruce