From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 70501 invoked by alias); 17 Apr 2018 20:03:00 -0000 Mailing-List: contact libc-alpha-help@sourceware.org; run by ezmlm Precedence: bulk List-Id: List-Subscribe: List-Archive: List-Post: List-Help: , Sender: libc-alpha-owner@sourceware.org Received: (qmail 70127 invoked by uid 89); 17 Apr 2018 20:03:00 -0000 Authentication-Results: sourceware.org; auth=none X-Virus-Found: No X-Spam-SWARE-Status: No, score=-2.0 required=5.0 tests=AWL,BAYES_00,RCVD_IN_DNSWL_NONE,SPF_PASS,URIBL_RED autolearn=ham version=3.3.2 spammy=HCC:D*de, increasing X-HELO: relay1.mentorg.com Date: Tue, 17 Apr 2018 20:03:00 -0000 From: Joseph Myers To: "H.J. Lu" CC: Carlos O'Donell , Florian Weimer , "Tsimbalist, Igor V" , GNU C Library Subject: Re: [PATCH] x86: Use pad in pthread_unwind_buf to preserve shadow stack register In-Reply-To: Message-ID: References: <61a5b452-e59e-dfef-4530-a94a60480961@redhat.com> User-Agent: Alpine 2.20 (DEB 67 2015-01-07) MIME-Version: 1.0 Content-Type: text/plain; charset="US-ASCII" X-ClientProxiedBy: svr-ies-mbx-01.mgc.mentorg.com (139.181.222.1) To svr-ies-mbx-01.mgc.mentorg.com (139.181.222.1) X-SW-Source: 2018-04/txt/msg00282.txt.bz2 On Fri, 6 Apr 2018, H.J. Lu wrote: > https://github.com/hjl-tools/glibc/commit/9bf6aefa8fb45f8df140d42ce9cf890bb24076e1 > > It should be binary backward compatible. I will investigate if there is a way Increasing the size of a public type is always dangerous, because you can end up with one part of a program expecting the new, larger size but another part only allocating the old, smaller size. It might in some cases be compatible to the extent that existing linked programs and shared libraries work with new glibc, if new glibc will never try to write into the unallocated part of such objects allocated by an existing linked program or shared library. However, any such change would need a careful analysis of how the type gets written to, and to what extent external libraries have interfaces that depend on the size of the type, and would need a NEWS entry explaining the change and discussing the compatibility issues with it. -- Joseph S. Myers joseph@codesourcery.com