Re: Removing glibc from the musl .2 ABI

[Rich Felker <dalias@libc.org>]

On Wed, Jul 17, 2019 at 08:13:44AM -0500, A. Wilcox wrote:
> On 07/16/19 22:37, Rich Felker wrote:
> > On Thu, Jul 11, 2019 at 06:58:38PM -0500, A. Wilcox wrote:
> >> (Full disclosure: I am the principal author of gcompat.)
> >>
> >> Hi,
> >>
> >> Now that gcompat has matured, I was wondering if perhaps musl should
> >> consider dropping the glibc ABI guarantees when the "2 ABI" lands.
> >>
> >> This would make the LFS64 symbol mess completely moot.
> > 
> > This is separate from the .2 ABI topic, but what would you think about
> > removing glibc ABI-compat from the current .1 ABI and replacing it
> > with enhanced gcompat? I was thinking ldso could load libgcompat
> > instead of returning a reference to itself for DT_NEEDED referencing
> > libc.so.6, and we could move all ABI-compat symbols into gcompat.
> > 
> > The reason I bring it up is that ripping out the LFS64
> > unwantedly-linkable stuff while keeping it as ABI-only is looking like
> > more of a pain than I expected.
> 
> We would be more than happy to work with you on that.
> 
> Would gcompat then become a runtime requirement for glibc apps on musl?
> What would musl do if gcompat isn't installed on a system?

It would just be a failed DT_NEEDED.

> What about
> things like libm and libdl, which I've seen some apps force DT_NEEDED
> anyway when built against musl?

These could still be ignored (mapped to internal libc) since any
program using them would also necessarily be using libc.so.6.

> Just trying to make sure the community has a clear view of what this
> looks like before we jump in.

Yes. This isn't a request to jump in, just looking at feasability and
whether there'd be interest from your side. Being that ABI-compat
doesn't actually work very well without gcompat right now, though, I
think it might make sense. I'll continue to look at whether there are
other options, possibly just transitional, that might be good too.

Rich