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Date: Sun, 10 May 2015 11:53:10 +0700
From: Рысь <lynx@...server.ru>
To: musl@...ts.openwall.com
Subject: Re: Should we support (not use, support) symbol versioning?

On Sat, 9 May 2015 22:18:38 -0400
Rich Felker <dalias@...c.org> wrote:

> On Sat, May 09, 2015 at 09:03:59PM -0400, Rich Felker wrote:
> > What we could possibly do, however, is honor the version requested
> > whenever the library being searched has version information. This
> > would allow third-party libraries that want to use versioning to do
> > so while also allowing unversioned libraries to satisfy any program
> > or library using them (and work correctly as long as it's using the
> > latest version API, just like now). However I'm mildly concerned
> > that symbol version tables could get introduced into libraries that
> > don't want them (including into libc.so) which would then horribly
> > break things, e.g. if any of libgcc.a's symbols were versioned (in
> > principle this should not happen, because they're all supposed to
> > be hidden, but I'm not really happy relying on that).
> 
> This risk is eliminated just by adding ldso.versym=0; after
> decode_dyn(&ldso) in the dynamic linker code, to ensure that any
> version tables that happen to creep into libc.so/ldso are ignored.
> 
> Rich

Symbol versions were so evil that enforced me to get rid all of them by
patching binutils' ld not to support them anymore and every package
which fails to build without them. I even have a small base of patches
for every package that happen to enforce them. And there are not many
of them. No breackage occured in this area after changes.

With glibc binaries however not such a nice picture. Simple ones which
rely not on glibc's internals probably are worked fine. An advanced ones
I happen to work with (nvidia drivers are example) crashed at end when
program called exit(), working fine before that. For that little time I
instead used another strategy: moved all glibc legacy runtime into
chroot with glibc. Now I cannot reproduce this anymore: no such system
exists today.

I rather think you should not even try to support these. Maybe musl can
became the competing libc which will force such recovery changes
someday.

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