Re: Linux vs. libio

[Mark Mitchell <mark at codesourcery dot com>]

>>>>> "Geoff" == Geoff Keating <geoffk@envy.cygnus.com> writes:

    Geoff> It may be that you will have to change glibc to be
    Geoff> compatible with the new layout.  You've already changed
    Geoff> glibc to be compatible with the new EH so you will be
    Geoff> requiring a new version of glibc anyway.

I think you mean the new atexit stuff.  Technically, that can go in
libstdc++, if necessary, and just replace the bits in libc.

But, you are correct -- in the end there will need to be a new libc.
It may or may not be deployed on IA32 Linux; that's not something I'll
decide.

However, I'm sure it will be deployed on IA64 Linux.  It's also likely
to be used on existing non-Linux platforms, like Solaris or IRIX.

Right now, I'm just trying to test the work, and the systems I have
handy are IA32 Linux.

    Geoff> You don't want to do that.  It would cause C stdio and C++
    Geoff> iostreams to be buffered separately causing output to be
    Geoff> interleaved wrongly.  It would also break the nice
    Geoff> stdio/iostreams interface that took so much work to get
    Geoff> right.

All these things are no doubt true.

I know why there's interdependency between these things, and I know we
want to keep that in the future.

However, libio has to change to match the new ABI.  That's a fact.
Obviously, this will be a conditionally compiled change; the
compiler's going to be supporting the old ABI indefinitely.  

It would be nice if people can use the new ABI, if only to test it, on
IA32 Linux.  They can't do that unless we can produce a version of
libio that doesn't interact with the C library, since we can't expect
everyone to go upgrading their C library.

--
Mark Mitchell                   mark@codesourcery.com
CodeSourcery, LLC               http://www.codesourcery.com