[boost] Need two new configuration macros

From: Daryle Walker (dwalker07_at_[hidden])
Date: 2003-06-06 01:09:15

I see the need for two new configuration macros.  The need popped up 
when I was trying to add a copy constructor to a stream buffer template 
class (for completeness) but GCC blocked it.

The std::basic_streambuf<> class template and the std::ios_base class 
don't mention any copying semantics in the standard.  This means that 
they automatically get a copy constructor.  However, DR 50 suggests 
that std::ios_base shouldn't be copyable.  (I think the reason was 
unclear semantics, and that all its derived types are non-copyable.)  
Recent versions of GCC block copying in ios_base, and they did the same 
to basic_streambuf.  (The latter was a side-effect; if everything else 
was non-copyable, why bother with copyable stream buffers.)

So now, we need macros to detect environments that implement DR 50.  We 
need two macros because only ios_base is directly involved, the 
treatment of basic_streambuf is an optional bonus.  From someone 
involved on GCC, he _thinks_ that the change happened in GCC 3.1, but 
may have happened earlier.

How would we express this macro?  Right now, I'm blocking my problem 
code with

#if !defined(__GNUC__) || (__GNUC__ < 3) || ((__GNUC__ == 3) && 
(__GNUC_MINOR__ < 1))

Any GCC experts here could correct, either in form, or the exact 
version the change happened.  We also need to know if any other 
compilers have added this change.

Daryle