From: "writeonce@midipix.org" <writeonce@midipix.org>
To: musl@lists.openwall.com
Subject: Re: musl-llvm and crtbegin/crtend
Date: Wed, 23 Apr 2014 04:47:55 -0400 [thread overview]
Message-ID: <53577E3B.9080902@midipix.org> (raw)
In-Reply-To: <20140422223811.GM26358@brightrain.aerifal.cx>
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
next prev parent reply other threads:[~2014-04-23 8:47 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-04-22 21:53 writeonce
2014-04-22 22:38 ` Rich Felker
2014-04-23 8:47 ` writeonce [this message]
2014-04-23 14:47 ` Rich Felker
2014-04-23 15:46 ` writeonce
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=53577E3B.9080902@midipix.org \
--to=writeonce@midipix.org \
--cc=musl@lists.openwall.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
Code repositories for project(s) associated with this public inbox
https://git.vuxu.org/mirror/musl/
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).