clang with libstdc++ doesn't have <tuple>

[marc.glisse@…]

Hello,

when I use a very recent clang with a very recent libstdc++ and a very recent boost, I still get BOOST_NO_0X_HDR_TUPLE defined. This seems to be because feature tests rely on __GNUC__ and __GNUC_MINOR__ to detect libstdc++ features. I understand that __GLIBCXX__ is hard to use. However, for this case, __has_include(<tuple>) would give a more reliable answer.

[John Maddock]

Frankly __GLIBCXX__ is functionally useless, I'm closing this as a duplicate of ​https://svn.boost.org/trac/boost/ticket/7473. However, it has given me the germ of an idea: please post follow up to the other ticket and test the patch there if you can. Thanks, John.