I do not believe that predef-check is working at all on the Android regression tests. Predef itself appears to be working as far as the predef macro values. But attempting to use predef-check to set a <cxxflags> value is just not happening. I can attest that just setting a <cxxflags> value, outside of using predef-check, does work correctly on the Android regression tests. The failure is occurring on my VMD tests. But you can also see the failure on the predef tests also. Looking at the info_as_cpp test output at http://www.boost.org/development/tests/develop/developer/CrystaX-NET-apileve... you can see that BOOST_COMP_CLANG > 0 and BOOST_OS_LINUX = 0. Yet if you look at the corresponding check_value test at http://www.boost.org/development/tests/develop/developer/CrystaX-NET-apileve... you will see that the output is 'CHECK_VALUE == undefined', whereas if predef-check were actually working the output should be 'CHECK_VALUE == 1' ( or 'true' ). In all other environments predef-check is working. Maybe this failure of predef-check somehow occurs because the Android tests are a cross-compile, being done on a Unix system but targeting the Android. But for whatever reason the inability of getting predef-check to work keeps my VMD tests from adding the '-std=c++0x' option and the VMD tests all fail without that option since the variadic macro support in VMD for gcc needs C++11 support or better.