On 1/14/2012 5:42 AM, Lorenzo Caminiti wrote:
On Sun, Dec 18, 2011 at 10:18 AM, Paul Mensonides<pmenso57@comcast.net> wrote:
On Sat, 17 Dec 2011 12:45:26 -0800, lcaminiti wrote:
Why does Boost.Preprocessor redefines BOOST_PP_VARIAIDCS instead of just using BOOST_NO_VARIADIC_MACROS from Boost.Config?
The pp-lib requires more than just superficial variadic macro support. I.e. BOOST_PP_VARIADICS macro is stronger.
Furthermore, GCC supports variadics also when C++11 extensions are not enabled so I think the following should not&& __GXX_EXPERIMENTAL_CXX0X__:
// File: boost/preprocessor/config/config.hpp # /* Wave (C/C++), GCC (C++) */ # elif defined __WAVE__&& __WAVE_HAS_VARIADICS__ || defined __GNUC__ && __GXX_EXPERIMENTAL_CXX0X__ # define BOOST_PP_VARIADICS 1
Because it isn't standard C++98. It can be enabled via a command line definition of BOOST_PP_VARIADICS. It is enabled by default (on GCC) when in C++11 mode. I believe that GCC 4.7 actually finally defines __cplusplus correctly as well.
It is annoying to manually -DBOOST_PP_VARIADICS. That is especially true for libraries like Boost.ScopeExit and Boost.Closure that use variadics in their public APIs so the end user is required to manually define BOOST_PP_VARIADICS when Boost.Preprocessor does not automatically detect it... (e.g., on GCC 4.5.3 without -std=c++0x).
You can just add: #define BOOST_PP_VARIADICS in your header files before using Boost PP headers. That isn't really that annoying to do if you want to force it.
Can we define what "extra" features are required by BOOST_PP_VARIADICS so I can write tests and run them to the Boost compilers and then refine the definition of BOOST_PP_VARIADICS to automatically detect all compilers where Boost.Preprocessor variadic support work.
Look at preprocessor/config/config.h for the internal logic for defining BOOST_PP_VARIADICS.