Bug#888073: glibc: Support amd64 systems without /lib64

[Michael Matz <matz@suse.de>]

Hi,

On Tue, 30 Jan 2018, Javier Serrano Polo wrote:

> El dl 29 de 01 de 2018 a les 16:24 +0000, Michael Matz va escriure:
> > Is does, but draft means many things, and for the psABI doesn't include 
> > "making backward incompatible changes is okay".
> 
> I am asking people to be nice, not requiring them to modify their
> systems. Let me try a new proposal:
> 
>         5.2.1
>         Systems conforming to the AMD64 ABI may want to support
>         the /lib/ld-linux-x86-64.so.2 path name, which is preferred in
>         multiarch.
> 
>         Appendix A.1
>         Systems conforming to the AMD64 ABI may want to support
>         lib/x86_64-linux-gnu subdirectories for the libraries, which are
>         preferred in multiarch.
> 
> This way, people that want to help will not be frowned upon.
> Could you do another assessment?

I think the addition to A.1 along the above lines would be fine.

But the change of 5.2.1 really can't be done.  Yes, the above wording 
makes it optional, so it sounds harmless, but it isn't, for the reasons I 
already called out: as soon as we allow executables with 
/lib/ld-linux-x86-64.so.2 as PT_INTERP to be conforming (even optionally) 
we split the world (into those that do support it, as allowed, and those 
that don't, as also allowed).  That must not happen.  We could fix that 
split by not only allowing, but instead _requiring_ that new name to exist 
on all conforming implementations.  Then the world won't be split, but it 
entails changes for everyone wanting to conform to the (newest version of 
the) psABI for dubious benefit, and so isn't something we would want 
either.

Perhaps we still can do something about the x32 program interpreter 
(currently defined to sit in /libx32/ld-linux-x32.so.2).  That is a 
relatively young addition and not many people use x32, so that could be 
moved to /lib to not repeat the problem of forcing a /libx32 directory on 
everyone even if they have other mechanisms.

But I fear for /lib64/ld-linux-x86-64.so.2 it's too late, it'd create 
larger problems (conforming programs not starting everywhere conforming) 
than it fixes (the cosmetic problem of a mostly empty /lib64 directory 
having to exist).


Ciao,
Michael.