#import, #pragma once to be removed in 3.4

[Zack Weinberg]

So we had a discussion of the problems that PCH poses for #import,
which expanded to a discussion of the problems of #import and
#pragma once generally, which then pretty much wound down without any
middle ground being found between 'there must be some way to fix it'
and 'no, sorry, there isn't'.  I think that an executive decision is
required at this point, which falls to me as cpplib maintainer.

Accordingly: #import and #pragma once will be removed from FSF GCC in
3.4.  I will shortly send a patch to gcc-patches to implement that.

I have heard the concerns of the people who have problems with the
remaining mechanism for idempotent #include, i.e. wrapper #ifndefs.
I have a solution in mind, but I would first like to determine how
widespread these problems are.  Please reply to this message
(do NOT cc: gcc-announce) if you have experienced problems with
collisions between macro names used in wrapper #ifndefs, or any other
technical problem with this mechanism.  Please also advise if you
could not work around the problem by editing the offending headers.

zw