Date: Sat, 6 May 2017 02:32:22 +1000 (EST) From: Bruce Evans <brde@optusnet.com.au> To: Ed Maste <emaste@freebsd.org> Cc: Konstantin Belousov <kostikbel@gmail.com>, Bruce Evans <brde@optusnet.com.au>, "src-committers@freebsd.org" <src-committers@freebsd.org>, "svn-src-all@freebsd.org" <svn-src-all@freebsd.org>, "svn-src-head@freebsd.org" <svn-src-head@freebsd.org> Subject: Re: svn commit: r317809 - head/share/man/man7 Message-ID: <20170506020904.P2496@besplex.bde.org> In-Reply-To: <CAPyFy2BX0T6OhwD5DE0DmunCBjN4XODKow_eECwk-6uYKynsfA@mail.gmail.com> 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> <CAPyFy2BX0T6OhwD5DE0DmunCBjN4XODKow_eECwk-6uYKynsfA@mail.gmail.com>
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On Fri, 5 May 2017, Ed Maste wrote: > On 5 May 2017 at 10:31, Konstantin Belousov <kostikbel@gmail.com> 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
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