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). 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. Thanks a lot. --Lorenzo