From mboxrd@z Thu Jan 1 00:00:00 1970 X-Msuck: nntp://news.gmane.org/gmane.linux.lib.musl.general/4948 Path: news.gmane.org!not-for-mail From: "writeonce@midipix.org" Newsgroups: gmane.linux.lib.musl.general Subject: Re: musl-llvm and crtbegin/crtend Date: Wed, 23 Apr 2014 04:47:55 -0400 Message-ID: <53577E3B.9080902@midipix.org> References: <5356E4CA.7060907@midipix.org> <20140422223811.GM26358@brightrain.aerifal.cx> Reply-To: musl@lists.openwall.com NNTP-Posting-Host: plane.gmane.org Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit X-Trace: ger.gmane.org 1398242896 5397 80.91.229.3 (23 Apr 2014 08:48:16 GMT) X-Complaints-To: usenet@ger.gmane.org NNTP-Posting-Date: Wed, 23 Apr 2014 08:48:16 +0000 (UTC) To: musl@lists.openwall.com Original-X-From: musl-return-4952-gllmg-musl=m.gmane.org@lists.openwall.com Wed Apr 23 10:48:11 2014 Return-path: Envelope-to: gllmg-musl@plane.gmane.org Original-Received: from mother.openwall.net ([195.42.179.200]) by plane.gmane.org with smtp (Exim 4.69) (envelope-from ) id 1Wcsqf-0003Qg-PU for gllmg-musl@plane.gmane.org; Wed, 23 Apr 2014 10:48:09 +0200 Original-Received: (qmail 9971 invoked by uid 550); 23 Apr 2014 08:48:07 -0000 Mailing-List: contact musl-help@lists.openwall.com; run by ezmlm Precedence: bulk List-Post: List-Help: List-Unsubscribe: List-Subscribe: Original-Received: (qmail 9963 invoked from network); 23 Apr 2014 08:48:07 -0000 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:24.0) Gecko/20100101 Thunderbird/24.4.0 In-Reply-To: <20140422223811.GM26358@brightrain.aerifal.cx> Xref: news.gmane.org gmane.linux.lib.musl.general:4948 Archived-At: On 04/22/2014 06:38 PM, Rich Felker wrote: > On Tue, Apr 22, 2014 at 05:53:14PM -0400, writeonce@midipix.org wrote: >> Greetings, >> >> First issue, and probably an easy fix, is the link to crtbegin.S and >> crtend.S on the musl wiki page entitled BuildingLLVM. The current >> links are broken, and should (probably) point to >> http://cvsweb.netbsd.org/bsdweb.cgi/src/lib/csu/ (the actual files >> are under arch/{$ARCH} >> >> More importantly, though: from very recent communication on the >> clang developer list, it is my understanding that the NetBSD >> crtbegin/crtend are the _de facto_ standard for self-hosting clang >> toolchains. If that is the case, does anyone know of a special >> license exception pertaining to these files? If I read the license >> correctly, then every binary containing the resulting crtbegin.o and >> crtend.o would have to include a copy of the license with its >> documentation. If there is such exception, then I'd suggest that >> the wiki page includes a link to it. > I'm not aware of this, but you might want to check and see if this > junk is even needed. My understanding is that these files do nothing > useful whatsoever unless you're using the old _init/_fini based > ctor/dtor system. GCC at least has switched to generating __init_array > and __fini_array which are much saner and I would guess clang has too. > > Note that these files aren't needed at all for pure C code anyway, > only for C++, GNU C, or other langs with static ctors/dtors. > > Rich > > Thanks, Rich. From the sources of gcc (4.6 -- 4.8) and llvm/clang (3.4 -- trunk) it appears that gcc introduced __init_array in version 4.7; when used, __do_global_ctors_aux is absent, however the implementation of __do_global_dtors_aux is still there (in crtbegin.o). When clang invokes the linker, it asks for crtbegin.o and crtend.o to be included regardless of the executable type (c/c++), which might be worth a patch (clang/lib/Driver/Tools.cpp). On the other hand, it does support __init_array (by default, I believe, and also through -fuse-init-array), and there are also relevant bits in the code for llvm's native linker (lld). Given that clang also supports the old ctor/dtor system (through -fno-use-init-array), the status of crtbegin/crtend seems to be still relevant. zg