3.3 ABI vs 3.4 ABI (!) vs 3.5 ABI (?)...

[Nathan Myers]

On Sat, Mar 06, 2004 at 11:31:11AM +0100, Paolo Carlini wrote:
>  1- Are there any hopes to provide some sort of smooth transition between
>     3.3 and 3.4? To wit, Michael noticed a few days ago that not that
>     many symbols present in 3.3-V3 are not anymore in 3.4. Perhaps, if
>     we really want, we can envisage providing "GLIBCXX_ABI Deprecated"
>     code, as we did between 3.2 and 3.3, or otherwise, fall back to
>     other strategies.  On one hand, this is, in my opinion, a "dirty
>     work" ;), which perhaps we would not really enjoy doing, on the
>     other hand, however, *so* many distributions relied and will rely
>     for some time still on 3.3 and therefore would be of *major*
>     benefit to the users.

There is no hope of link compatibility between 3.3 and 3.4.  However, we 
can urge the distros to include a 3.4 version of libstdc++.so (too), and 
promise (in exchange) not to change that ABI for a longish time.

>  2- 3.4 vs 3.5: what shall we do? This issue is not less urgent, since 
>     shapes the kind of development that will happen in mainline and/or
>     the need of backporting to 3.4 any ABI-breaking change that in the
>     next few weeks of mainline developmente turns out to be really
>     unavoidable.  Personally, I'm particularly worried by locale and
>     string, which have already diverged quite a bit (hopefully still
>     not too much from the ABI point of view), but other areas are
>     affected as well.

This seems entirely do-able.  Backports should be easy in any case,
because none of the improvements depend on compiler fixes 3.4 vs 3.5;
but most of the recent locale work does not, I think, affect the ABI.

Nathan Myers
ncm-nospam@cantrip.org