I confess to not understanding how the config tests work. When I run "bjam toolset=gcc-4.4 config_test" in libs/config/tests, the tests pass whether or not S_NO_SFINAE_EXPR is defined for gcc-4.4. I'm clearly doing something wrong.
Looks like the test is not good enough then. (I was the one who wrote that particular test, but I don't quite understand the Boost.Config testing mechanism either)
Sigh... it's very imperfect: * By default the only tests that are run check that config_test.cpp compiles, which means either: the macro is set or the code compiles and runs. * There are tests that check the reverse (ie which will fail if a macro is set when it should not be), but they are not run by default because they aren't 100% reliable - in large part because we don't have a suitable Boost.Build testing rule. John.