Two questions related to C++ ABI transition

[Ming Hua <minghua-list@sbcglobal.net>]

Hello,

One package I maintain (libscim8 from scim) is going through the c2->c2a
C++ ABI transition.  I have two questions about the dependency handling
in such a transition:

1. Raised by my sponsor - Should I add g++ (>= 4.0.2-4) to the
Build-Depends? I did not do so, and my sponsor asked why not.  The only
reason I could find was from the previous c102->c2 transition plan [1]:
"Please don't add build dependencies on g++ (>= 4.0) or build-essential
(>= 11)", there is no such instruction this time.

One thing I can think of is that adding g++ (>= 4.0) or (>= 4.0.2-4)
actually prevent building the package with g++-3.4, although they have
the same ABI as the g++-4.0.  But that doesn't explain when I shouldn't
build-depend build-essential (>= 11).  And I agree with my sponsor that
such dependency avoids accidently building them with wrong ABI.  So can
somebody explain why such dependency is not desired?

[1] http://lists.debian.org/debian-devel-announce/2005/07/msg00001.html

2. Once the library package is built with the new ABI, should I tighten
the build-dependency of the application packages that depend on the
transitioned library?  Tightening the build-dependency will again ensure
that the package is built with the correct ABI, but it also makes the
package unbuildable in an old pre-transition environment even with the
old libraries.  As the plan is to binNMU these application packages, it
seems a tightened build-dependecy is not urgent after all, but are they
preferred eventually?

Thanks in advance,
Ming
2005.12.02