mailing list of musl libc
 help / color / mirror / code / Atom feed
From: Florian Weimer <fweimer@redhat.com>
To: musl@lists.openwall.com
Subject: Re: Symbol versioning approximation trips on compat symbols
Date: Thu, 24 Jan 2019 12:18:12 +0100	[thread overview]
Message-ID: <87sgxi718r.fsf@oldenburg2.str.redhat.com> (raw)
In-Reply-To: <20190124110931.GU21289@port70.net> (Szabolcs Nagy's message of "Thu, 24 Jan 2019 12:09:32 +0100")

* Szabolcs Nagy:

> but it turned out to be broken (ifunc resolvers may run before
> relocations for the extern object are processed), so the symbol
> was removed (moved to libgcc.a), but a compat symbol (@) was
> kept around and the ctor of libgcc_s.so.1 still references it.

I assume we cannot use a hidden alias to eliminate the symbolic
reference because it is a data symbol, so copy relocations are a
possibility and with the hidden alias, the constructor would update the
wrong object?

> i wonder what is the use-case for using a compat symbol without
> introducing a new default version for the symbol in general?

A compat symbol can be implemented by a different library, and
applications can link to the symbol and get it from the new library.

Mostly it is just for documenting intent, marking the symbol as
deprecated.  It's still relatively easy to link to the symbol from new
binaries (even without resorting to dlvsym).

Thanks,
Florian


  reply	other threads:[~2019-01-24 11:18 UTC|newest]

Thread overview: 26+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-01-21 17:57 Florian Weimer
2019-01-24  1:43 ` Rich Felker
2019-01-24  9:28   ` u-uy74
2019-01-24 10:11     ` Florian Weimer
2019-01-24 11:09   ` Szabolcs Nagy
2019-01-24 11:18     ` Florian Weimer [this message]
2019-01-27  4:04       ` Rich Felker
2019-01-27  9:36         ` u-uy74
2019-01-28  6:34           ` Florian Weimer
2019-01-28  9:17             ` Timo Teras
2019-01-28 11:33               ` Szabolcs Nagy
2019-01-28 12:40             ` Szabolcs Nagy
2019-01-28 13:08             ` (OT?) Re: [musl] " u-uy74
2019-01-28 15:22               ` Markus Wichmann
2019-01-28 15:34                 ` Rich Felker
2019-01-28 15:29               ` Rich Felker
2019-01-29 17:13                 ` u-uy74
2019-01-30 14:57                   ` Rich Felker
2019-01-28 21:57             ` A. Wilcox
2019-01-28 22:52               ` Matias Fonzo
2019-01-28 23:12                 ` Zach van Rijn
2019-01-28 23:41                   ` A. Wilcox
2019-01-28 23:47                     ` Rich Felker
2019-01-29  3:22                       ` A. Wilcox
2019-01-29 19:40                         ` Matias Fonzo
2019-01-29 19:31                   ` Matias Fonzo

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=87sgxi718r.fsf@oldenburg2.str.redhat.com \
    --to=fweimer@redhat.com \
    --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).