libstdc++ ABI break

[Benjamin Kosnik]

> On Fri, Oct 05, 2007 at 05:49:03PM -0700, Mark Mitchell wrote:
> > Other than this, is the 4.2.x libstdc++ actually ABI-compatible with
> > 4.1.x?  

Yes.

> > Is there any evidence that people are actually mixing and
> > matching in that way?  I'm not asking if the libstdc++ ABI tests
> > pass; I'm asking if we actually know that people are actually
> > mixing things. Like, are people building Qt applications with 4.2
> > and linking them to 4.1 libstdc++?

We don't support this specific scenario.

We do support people building Qt applications with 4.1 and
linking them to 4.2 libstdc++. 

> The tests that caught this are not the C++ ABI tests.  They're the LSB
> (Linux Standard Base) library ABI tests, which are designed to let a
> large number of vendors find a common ABI to work on a large number of
> distributions.  So I think you can take it as certain that there will
> be people running LSB-compliant applications on both GCC 4.2 and GCC
> 4.2.1.

Yep. I think it will be much easier to fix this in 4.2.2, and point out
4.2.1 as a possible singularity, than to continue with this
unintentional change.

> No one's noticed it yet, but it would be a pretty nasty bug to track
> down, and the affected release was only made ten weeks ago; it hasn't
> been widely picked up yet.  I'm sure it will be.  The people who have
> already picked it up are hopefully still using it for test releases.
> 
> I recommend Ben's patch.

Me too. Mark, I wait for your ok.

This is now 

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=33678

-benjamin