Re: -fnew-abi and branching

[Mark Mitchell <mark at codesourcery dot com>]

>>>>> "Benjamin" == Benjamin Kosnik <bkoz@fidel.cygnus.com> writes:

    >> | In private email, Jason suggested that doing the -fnew-abi |
    >> development (i.e., the parts that belong to the compiler, not
    >> the bits | we discussed regarding libio) need not be done on a
    >> branch.

    Benjamin> I am also in favor of this.

Great.  Since Jeff has also approved this idea, I think we've got a
quorum.

    Benjamin> Will -fhonor-std still work? That's the flag that most

Yes.

    Benjamin> concerns me, and I suspect that it is not going to be
    Benjamin> affected. Since -fnew-abi turns on a bunch of things,
    Benjamin> perhaps you can elaborate on what flags will and will
    Benjamin> not work (ie, I suspect -fvtable-thunks will break, but
    Benjamin> that -fsquangle will not really change due to the new
    Benjamin> ABI).
 
Right.  Although the new ABI will specify a mangling scheme.  I
suspect that we'll just implement it "from scratch" since the current
mangling code is a disaster.  We really want to get the mangling
"right" according to the spec.  That means we can decide later whether
to support mangling, squangling, and the new scheme -- or just some
some subset of the three.

In the short run, location of vtbl pointers will change.  Location of
base classes will change.  Vtable layout will change.  Virtual base
pointers will be eliminated.

Then, some run-time library changes will occur -- but in the part of
the library that comes with EGCS.  Things like RTTI and
exception-handling.

    Benjamin> Again, as long as -fsquangle -fhonor-std work, I don't
    Benjamin> think it's a big deal. People can always use
    Benjamin> gcc-2.95.2. . . I don't see how this can be helped.

Me neither.  I'm glad you agree.

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