Re: [9fans] acme, rio workalike available in plan 9 ports

[Christoph Hellwig <hch@sgi.com>]

On Fri, Apr 23, 2004 at 03:56:03PM +0000, ron minnich wrote:
> I think unless I'm wrong that you've actually demonstrated the problem I'm
> trying to show -- an old binary, using a broken interface, doesn't get
> fixed just because you update the library. What happens is that the old
> binary retains the broken interface. This is not what people think of with
> shared libraries -- they naively think you upgrade the library and good
> things happen, bugs are fixed, angels sing. glibc retains old broken
> interfaces as time moves forward -- is this really a good idea?

I think this depends on your defintion of broken.  E.g. if FILE grows
to support $RANDOM new feature is the old interface broken because of
that?  If I had a third party program on my system that I don't have
sources for I'd be more than happy to keep that supported, yes.

I think I understand your point, but it looks more like a thoeretical
issue than something that comes up in practice.    Yes, symbol
versioning does allow you to keep the old version around, as do weak
symbols if you overrode it in your program, etc..  The thing is that
the way it's used in practice works different.

> In other words, shared libraries certainly solve a problem, but I'm not
> sure any more which one it is.

They still allow you to fix problems in a central place.  Just because
you might have two versions of the same symbol that doesn't mean you're
magically unable to fix them.