I have included and linked the latest Boost C++ library into my build. I tested the library beforehand. However, when simply including the header files in a C++ actor class in my Unreal game project, I get errors like: Warning Example: Error boost/config/stdlib/dinkumware.hpp(99) : warning C4668: '_HAS_NAMESPACE' is not defined as a preprocessor macro, replacing with '0' for '#if/#elif' Error Examples: Error boost/intrusive/slist.hpp(1926) : error C4003: not enough actual parameters for macro 'check' Error boost/intrusive/slist.hpp(1926) : error C2062: type 'void' unexpected It looks like there is some strict/unsupported semantic issues with the compiler that is being used. How do I fix this? I am on Windows with VS 2017. Sample programs compile fine with just cl /EHsc /I boost_1_64_0 test_game.cpp /link /LIBPATH:"F:\boost_1_64_0\stage\lib" Why would the compiler not work from within Unreal? Thanks, Regards, James