[cxx-abi-dev] Question about tail padding

[Jim Dehnert]

I won't take a position on the right answer to this problem, but I
can provide some of the motivation from the original discussion.

The original concern was with the packing of very small objects,
e.g. segmented addresses and the like for system programming.  The
primary concerns were, not surprisingly:

- Ability to represent packing:  If you don't reuse the tail padding,
  sharing storage units may be impossible across classes, possibly
  forcing undesired redefinition; whereas if you do it is easily
  disabled by adding explicit padding members.

- Performance of things like copy constructors, or more precisely,
  the surprise factor that performance may be unexpectedly bad, given
  that explicit padding can again avoid the problem.

The capability argument won at the time, though I don't recall for
sure whether the intent was to go to bit level or just to the byte
level.

Jim

-- 
-	    Jim Dehnert		dehnert at transmeta.com
	    (408)919-6984	dehnertj at acm.org