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Re: C++ ABI Issues

--On Monday, August 26, 2002 08:28:38 PM -0700 Benjamin Kosnik <> wrote:


I propose that we fix G++ to match the ABI, but that we issue warnings
about classes whose layout has changed from GCC 3.2.

If we are going to fix G++, we also have to decide how urgently to do
another release.
You seem to be very cavalier about the downstream impacts of changing
the C++ ABI, and what this means for sane tool versioning.
I tried to bring these issues to the attention of the GCC community
promptly, and to present some realistic assessment of how important
they are, or are not.

Certainly, one reasonable position is to do nothing.  Another is to
(as several have suggested) support both modes (which seems like
a good idea to me).  Another is my initial suggestion (to fix the
problems right away.)  To me, the best argument for my suggestion is
that at this point there aren't too many people dependent on 3.2; the
longer we leave it around the harder it may to be change it later.

Your point, made previous by Joe, that we are likely to find more bugs,
is also a very good one.

I recently had discussions with folks at HP about what to do when these
things come up.  They've got an almost-compliant compiler deployed in
the field; so do we.  They're very interested in being compatible with
GCC.  Nobody wants to break things for their users.  It's a difficult
situation, and the discussions didn't reach an easy solution -- although
everyone was very clear that the ultimate goal is to keep from messing
up things for users.  I'd love it if we had a process in place to deal
with these issues when they arise.

I don't have a strong opinion about what we do at this point; I'm happy
to see what the consensus is and do whatever that is.  At this point,
it looks like people are leaning towards David's -fabi-with-fewer-bugs
switch, which is fine by me.

Mark Mitchell      
CodeSourcery, LLC  

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