From mboxrd@z Thu Jan 1 00:00:00 1970 Path: news.gmane.org!not-for-mail From: Stefan Monnier Newsgroups: gmane.emacs.devel Subject: Re: Dumper problems and a possible solutions Date: Wed, 25 Jun 2014 19:05:14 -0400 Message-ID: References: <20140624171955.GS179@brightrain.aerifal.cx> <53AB0EF8.4090608@yandex.ru> <831tucrguf.fsf@gnu.org> <20140625183241.GW179@brightrain.aerifal.cx> <83wqc4q0xl.fsf@gnu.org> <20140625190333.GZ179@brightrain.aerifal.cx> <20140625202403.GB179@brightrain.aerifal.cx> <20140625220758.GE179@brightrain.aerifal.cx> NNTP-Posting-Host: plane.gmane.org Mime-Version: 1.0 Content-Type: text/plain X-Trace: ger.gmane.org 1403737555 26245 80.91.229.3 (25 Jun 2014 23:05:55 GMT) X-Complaints-To: usenet@ger.gmane.org NNTP-Posting-Date: Wed, 25 Jun 2014 23:05:55 +0000 (UTC) Cc: Eli Zaretskii , dmantipov@yandex.ru, emacs-devel@gnu.org To: Rich Felker Original-X-From: emacs-devel-bounces+ged-emacs-devel=m.gmane.org@gnu.org Thu Jun 26 01:05:48 2014 Return-path: Envelope-to: ged-emacs-devel@m.gmane.org Original-Received: from lists.gnu.org ([208.118.235.17]) by plane.gmane.org with esmtp (Exim 4.69) (envelope-from ) id 1WzwGA-0008VU-3H for ged-emacs-devel@m.gmane.org; Thu, 26 Jun 2014 01:05:46 +0200 Original-Received: from localhost ([::1]:41451 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1WzwG9-0000X4-Lu for ged-emacs-devel@m.gmane.org; Wed, 25 Jun 2014 19:05:45 -0400 Original-Received: from eggs.gnu.org ([2001:4830:134:3::10]:33124) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1WzwFv-0000W5-0U for emacs-devel@gnu.org; Wed, 25 Jun 2014 19:05:38 -0400 Original-Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1WzwFn-0006Iq-Ah for emacs-devel@gnu.org; Wed, 25 Jun 2014 19:05:30 -0400 Original-Received: from ironport2-out.teksavvy.com ([206.248.154.181]:27080) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1WzwFf-0006Hl-G2; Wed, 25 Jun 2014 19:05:15 -0400 X-IronPort-Anti-Spam-Filtered: true X-IronPort-Anti-Spam-Result: ArUGAIDvNVNLd+D9/2dsb2JhbABZgwaDSsA9gRcXdIIlAQEBAQIBJy8jBQsLDiYSFBgNJC6HVgjSGReOegeEOASpGYFqg0wh X-IPAS-Result: ArUGAIDvNVNLd+D9/2dsb2JhbABZgwaDSsA9gRcXdIIlAQEBAQIBJy8jBQsLDiYSFBgNJC6HVgjSGReOegeEOASpGYFqg0wh X-IronPort-AV: E=Sophos;i="4.97,753,1389762000"; d="scan'208";a="69568389" Original-Received: from 75-119-224-253.dsl.teksavvy.com (HELO ceviche.home) ([75.119.224.253]) by ironport2-out.teksavvy.com with ESMTP/TLS/ADH-AES256-SHA; 25 Jun 2014 19:05:14 -0400 Original-Received: by ceviche.home (Postfix, from userid 20848) id 5A80766302; Wed, 25 Jun 2014 19:05:14 -0400 (EDT) In-Reply-To: <20140625220758.GE179@brightrain.aerifal.cx> (Rich Felker's message of "Wed, 25 Jun 2014 18:07:58 -0400") User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/24.4.50 (gnu/linux) X-detected-operating-system: by eggs.gnu.org: Genre and OS details not recognized. X-Received-From: 206.248.154.181 X-BeenThere: emacs-devel@gnu.org X-Mailman-Version: 2.1.14 Precedence: list List-Id: "Emacs development discussions." List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: emacs-devel-bounces+ged-emacs-devel=m.gmane.org@gnu.org Original-Sender: emacs-devel-bounces+ged-emacs-devel=m.gmane.org@gnu.org Xref: news.gmane.org gmane.emacs.devel:172735 Archived-At: >> - we're still talking about performing relocation of all heap references >> during startup (not that it's a problem, of course). Maybe we don't >> need to do it ourselves, but it still has to happen. > Indeed. The difference is just between having to write non-portable > code that does it manually, and having it happen automatically as > consequences of the requirements of the C language. The manual code would be fairly normal C code, very similar to the mark_object routine. It shouldn't be noticeably less portable than the current pointer<->int conversions we use for tagging purposes. Of course, it's always nice when we can use someone else's code, but I get the impression that to get the right behavior from the compiler/linker/loader we may have to generate a fairly enormous C file which will generate an enormous .o file and the resulting binary will end up with a humongous relocation table. Of course, only time will tell. > My understanding is that the tagged references are using the low bits > of otherwise-aligned pointers as flags. Is this correct? If so, then > these are just constant offsets applied to an address, and thus they > are still valid C address constant expressions, so they have to be > supported. Indeed, it might work. Stefan