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Date: Tue, 9 Apr 2013 13:19:12 -0400
From: Rich Felker <>
Subject: Re: Pending issues for next release

On Thu, Apr 04, 2013 at 07:04:04PM -0400, Rich Felker wrote:
> On Wed, Apr 03, 2013 at 09:00:00PM -0700, Isaac Dunham wrote:
> > On Mon, 1 Apr 2013 19:31:44 -0400
> > Rich Felker <> wrote:
> > 
> > > Here's a quick list of open issues that we might want to take care of
> > > before another release:
> > >
> > (snipping several interesting improvements) 
> > > - switching symlink direction
> > 
> > Does this patch look suitable?
> > I know it does work, including in the DESTDIR=./.../ case.
> I can't say it's wrong, but seeing this patch reminds me why I didn't
> do it before...
> > diff --git a/Makefile b/Makefile
> > index 997c5bb..478e698 100644
> > --- a/Makefile
> > +++ b/Makefile
> > @@ -118,7 +118,10 @@ tools/musl-gcc: config.mak
> >  $(DESTDIR)$(bindir)/%: tools/%
> >  	install -D $< $@
> >  
> > -$(DESTDIR)$(libdir)/ lib/
> > +$(DESTDIR)$(libdir)/ $(DESTDIR)$(LDSO_PATHNAME)
> > +	ln -sf $(LDSO_PATHNAME) $@
> > +
> >  	install -D -m 755 $< $@
> >  
> >  $(DESTDIR)$(libdir)/%: lib/%
> > @@ -127,12 +130,6 @@ $(DESTDIR)$(libdir)/%: lib/%
> >  $(DESTDIR)$(includedir)/%: include/%
> >  	install -D -m 644 $< $@
> >  
> > -$(DESTDIR)$(LDSO_PATHNAME): $(DESTDIR)$(syslibdir)
> > -	ln -sf $(libdir)/ $@ || true
> > -
> > -$(DESTDIR)$(syslibdir):
> > -	install -d -m 755 $(DESTDIR)$(syslibdir)
> > -
> Unfortunately, this makes it impossible to run "make install" without
> a DESTDIR unless you're root. Before, the ||true in the dynamic-linker
> installation allowed you to "make install" without root as long as you
> have permissions to the prefix, and the resulting install could be
> used for everything except _running_ dynamic-linked programs. (Also,
> if root added a single symlink for you, it would be fully functional.)
> I don't want to reject the patch, because I think this change is
> mostly correct, but I would like to discuss and see if there's any way
> we can get back the old level of functionality while making this
> change. In particular, users should be able to install musl with
> --prefix=$HOME/musl and build binaries which will run on any system
> with the musl loader in /lib.

Do you have any good ideas for what we should do here? Some folks on
IRC have also been asking about the motivations for the change. The
ones I recall are:

1. (not a valid reason) Debian policy. As long as a Debian package for
musl is making its own lib dir (e.g. /usr/musl/lib or whatever) I
think it's exempt from policy on library versioning, just like firefox
or something that has package-local .so files.

2. Versioning. It's impossible to have multiple versions installed
simultaneously. However, I don't see how the proposed change would
help. /lib/ld-musl-$(ARCH).so.1 is not versioned either. The ".1" is
not a version that will change (unless we had a major new ABI) but
rather a silly convention. So I don't think this is a valid reason for
the change anyway, though it could be a valid reason for _alternate_

3. Performance. Having the PT_INTERP be a symbolic link adds a
symbolic link dereference in each exec() syscall for a dynamic linked
program. In theory, avoiding that should shave some time off exec().

4. Allowing $(libdir) on non-root partition.

The alternate change I came up with that would address issue 2, but
not 3 or 4, is making the real file be $(libdir)/musl-$(VERSION).so or
similar, and having both and ld-musl be symlinks to it.
However this also has the negative aspect of requiring the symlink in
$(syslibdir) to change with each upgrade, which is frustrating if
you're trying to allow a single user to upgrade musl without write
permission to /lib.

If there are no good solutions right now, I think it may be best to
leave this issue alone for the time being. But if a change is going to
be made, I want it to happen as far away from 1.0 as possible, so
please start thinking about good ideas for how this should work! :)


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