3.4 to 3.5 libstdc++ changes

[Paolo Carlini]

Benjamin Kosnik wrote:

>Paolo recently asked about this. Here's my take on the current status
>between 3.4 and 3.5.
>  
>
Thanks Benjamin for your summary.

Well, some of those changes are minor, many do not affect the ABI, and 
can be
backported safely for 3.4.1.

Some, OTOH, more substantial, *do* affect the ABI but, at the same time, we
feel are real improvements and were already scheduled, more or less 
explicitly,
long ago (e.g., allocator, __moneypunct). What can we realistically do 
at this
point?

I had hopes of forward compatibility, but there are many removed/changed 
symbols,
sadly :( If the release manager gives us some days, perhaps we can try, 
taking some
risks if we don't want just to undo the mainline improvements but 
instead backport
in a sensible way the ABI changing bits, if not the entire work (seems 
unlikely, at
this point).

Or give up, setting 3.5 (aka 4.0?) as a target for the ABI: as far as 
I'm concerned,
at least we could have all the facets cached and this round of 
basic_string work
completed (non-refcount switch, simplification of the modifying members, 
etc.)

Which is your take?

Paolo.