From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 122078 invoked by alias); 5 Mar 2018 22:00:48 -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 121841 invoked by uid 89); 5 Mar 2018 22:00:35 -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= X-HELO: relay1.mentorg.com Date: Mon, 05 Mar 2018 22:00:00 -0000 From: Joseph Myers To: Helmut Grohne CC: Subject: Re: state of the install-bootstrap-headers patch In-Reply-To: <20180305203511.GA25373@alf.mars> Message-ID: References: <20180305203511.GA25373@alf.mars> 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-02.mgc.mentorg.com (139.181.222.2) To SVR-IES-MBX-03.mgc.mentorg.com (139.181.222.3) X-SW-Source: 2018-03/txt/msg00131.txt.bz2 On Mon, 5 Mar 2018, Helmut Grohne wrote: > I'm wondering about the state of a patch that adds a flag > "install-bootstrap-headers" to the Makefile. Let me first try to > summarize the problem, then the solutions taken by various Linux > distributions and then proceed to asking how to move forward. install-bootstrap-headers was part of an obsolete process for bootstrapping cross toolchains including glibc, which involved three GCC builds (a first static-only build with inhibit_libc which was used to configure glibc to install bootstrap headers, crt*.o and a dummy libc.so, which allowed a second build including shared libgcc, which could be used to build and install a full glibc and so allow building the third GCC including support for non-C languages). The conclusion of the discussion of install-bootstrap-headers was to obsolete that process by enabling a two-GCC process: that is, enabling the initial static-only C-only GCC to build a complete glibc, with the installed stripped glibc binaries being byte-for-byte identical to those you get from a longer alternating sequence of GCC and glibc builds (in particular, with no dependence on the existence of libgcc_s.so at the time glibc is built). As of glibc 2.16 and GCC 4.9 this is fully supported. (For some configurations you need the --with-glibc-version configure option to be passed when configuring the static-only GCC so that it knows what glibc version to expect to be used; in particular, this is required for configurations where GCC has architecture-specific SSP support. For ia64 you may need GCC 5 for inhibit_libc builds to work at all.) This modern bootstrap process is illustrated by what the build-many-glibcs.py script does. > The patches are in circulation since around 2007 and were reposted in > 2012: https://sourceware.org/ml/libc-alpha/2012-03/msg00237.html The > later discussion wound down figuring whether gcc or glibc should deal > with it and it ended in some dreaming at: > https://sourceware.org/ml/libc-alpha/2012-03/msg00960.html While not everything there (which would allow just *one* GCC build in such a bootstrap case) has been implemented, enough has been implemented to obsolete the three-GCC-build process, and thus to obsolete install-bootstrap-headers. -- Joseph S. Myers joseph@codesourcery.com