Rob Stewart wrote:
Add feature macros and test for them. The macros can be defined when the header is fully supported or for particular compilers.
If you're agreeing with Beman that BOOST_NO_CXX11_HDR_ATOMIC should not be defined when <atomic> is not 100% conforming, then I disagree. We do not have a practice of saying, via macros, that a header isn't present, and then saying, via other macros, that it actually is. BOOST_NO_CXX11_HDR_ATOMIC means that #include <atomic> would fail. Not defining it when the header is present but not useful, while a typical practice for us, is not the right thing to do when libraries disagree on whether the header is useful. When a header contains more than one feature, and some of them may be present while others may not be, we supply feature macros instead of a header macro. The lack of BOOST_NO_CXX11_ATOMIC_FEATURE means that #include <atomic> would work and provide $FEATURE.