[Boost-users] warning C4275, C4271when using boost::noncopyable

Hi All, I'm trying to update from boost 1.62 to boost 1.73. Boost 1.62 was built with VS15 140 toolchain with shared runtime (/MD) and as static lib. Boost 1.73 was built with VS19 140 toolchain with /MD and as static lib. I have a class: #include <boost/noncopyable.h> class __declspec(dllexport) A : private boost::noncopyable when I'm using 1.62 I do not have such warning. when I'm using 1.73 I do have such warning. I'll appreciate if anyone could help me to understand what I'm missing. Why does new version of header generate this warning? Thanks, Roman