[boost] Re: config.h[pp]

From: Reid Sweatman (reids_at_[hidden])
Date: 1999-07-13 14:16:18

Looks good to me, although I suspect there are more things not supported by
VC++ in any version than just member templates.  Just have a look at the MS
section in SGI's STL config header (BTW, do you have to explicitly include
that header somewhere, or is it implicitly included by the other headers?  I
can find no docs that mention it, and the code is Byzantine, to say the
least).

In that vein, can anyone here explain exactly *what* you do to work around a
compiler (like VC++) that doesn't support pointer operators on iterators?  I
get inconsistent behavior from SGI STL, in that I can't explicitly reference
the innards of a compound object given an iterator to it, but the [ ]
operator works just fine, although internally it's implemented with an
iterator pointer (this is with the hash_map class, but it would probably
come up with *any* iterator object).

> -----Original Message-----
> From: Beman Dawes [mailto:beman_at_[hidden]]
> Sent: Tuesday, July 13, 1999 5:41 AM
> To: Boost.org mailing list
> Subject: [boost] config.h[pp]
> 
> 
> If this was a perfect world, or a standards committee, I wouldn't
> have to be writing this message.  But in the real world, where
> compilers don't all conform to standards, we need a way to specify
> compiler configuration information.
> 
> While few like doing so, the most practical way of coping with small
> platform dependencies is via macros.  Both program maintenance and
> porting costs are minimized by defining the macros in a single
> configuration file.
> 
> For example, boost/smart_ptr.h uses member templates if available,
> controlled by the definition or lack of a macro
> BOOST_NMEMBER_TEMPLATES.  So that most users to not need to even know
> about this possible compiler shortcoming, smart_ptr.h should #include
> <boost/config.h> (or whatever name).
> 
> Here is a first cut at config.h.  Comments appreciated.
> 
> --Beman
> 
> --------
> 
> //  Boost configuration header file
> -----------------------------------------//
> 
> //  (C) Copyright Boost.org 1999. Permission to copy, use, modify,
> sell and
> //  distribute this software is granted provided this copyright
> notice appears
> //  in all copies. This software is provided "as is" without express
> or implied
> //  warranty, and with no claim as to its suitability for any
> purpose.
> 
> //  See http://www.boost.org for most recent version including
> documentation.
> 
> //  This header is used to pass configuration information to other
> boost files,
> //  to allow them to cope with platform dependencies such as compiler
> //  shortcomings.
> //
> //  Centralized configuration reduces the number of files which must
> be modified
> //  when porting libraries to new platforms, or when compilers are
> updated.
> //
> #ifndef BOOST_CONFIG_H
> #define BOOST_CONFIG_H
> 
> //  Flag macros should identify the absence of C++ Standard
> conformance rather 
> //  than its presence.  This ensures that standard conforming
> compilers do not
> //  require a lot of configuration flag macros.  It places the burden
> where it
> //  should be, on non-conforming compilers.  It means, hopefully,
> that in the 
> //  future less rather than more conformance flags will have to be
> defined.
> 
> //  Flag Macros
> -------------------------------------------------------------//
> //
> //  BOOST_NMEMBER_TEMPLATES: define if compiler doesn't support
> member templates
> 
> //  Compilers are listed in alphabetic order
> --------------------------------//
> 
> //  Microsoft (excluding Intel/EDG front end)
> -------------------------------//
> 
> # if defined( _MSC_VER ) && (!defined( __ICL )
> #   if _MSC_VER <= 1200  // 1200 == VC++ 6.0
> #     define BOOST_NMEMBER_TEMPLATES
> #   endif
> # endif // Microsoft (excluding Intel/EDG frontend) 
> 
> #endif  // BOOST_CONFIG_H
> 
> 
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