I've just downloaded boost_1_52_0_beta1 and get the warning below in my user code on VC11(I'm using thread which evidently brings in the above libs). I didn't see mention of this in trac. I'm moving forward from 1.47 and from VC8 so I'm not sure if this is an indication of some project setting[s] of mine, or if it should be corrected in the lib? Thanks, Jeff 6>D:\boost_1_52_0_beta1\boost/ratio/detail/overflow_helpers.hpp(136): warning C4293: '<<' : shift count negative or too big, undefined behavior 6> D:\boost_1_52_0_beta1\boost/ratio/detail/overflow_helpers.hpp(282) : see reference to class template instantiation 'boost::ratio_detail::br_mul<X,Y>' being compiled 6> with 6> [ 6> X=0x01, 6> Y=0x01 6> ] 6> D:\boost_1_52_0_beta1\boost/ratio/ratio.hpp(155) : see reference to class template instantiation 'boost::ratio_detail::ratio_divide<R1,R2>' being compiled 6> with 6> [ 6> R1=boost::ratio<0x01,0x0989680>, 6> R2=boost::ratio<0x01,0x03e8> 6> ] 6> D:\boost_1_52_0_beta1\boost/chrono/duration.hpp(305) : see reference to class template instantiation 'boost::ratio_divide<R1,R2>' being compiled 6> with 6> [ 6> R1=boost::ratio<0x01,0x0989680>, 6> R2=boost::ratio<0x01,0x03e8> 6> ] 6> D:\boost_1_52_0_beta1\boost/chrono/duration.hpp(784) : see reference to class template instantiation 'boost::chrono::detail::duration_cast<FromDuration,ToDuration>' being compiled 6> with 6> [ 6> FromDuration=boost::chrono::duration<int_least64_t,boost::ratio<0x01,0x0989680>>, 6> ToDuration=boost::chrono::milliseconds 6> ] 6> D:\boost_1_52_0_beta1\boost/chrono/ceil.hpp(27) : see reference to function template instantiation 'boost::chrono::duration<Rep,Period> boost::chrono::duration_cast<To,int_least64_t,boost::ratio<N,D>>(const boost::chrono::duration<Rep,boost::ratio<N,D>> &)' being compiled 6> with 6> [ 6> Rep=int_least64_t, 6> Period=boost::milli, 6> To=boost::chrono::milliseconds, 6> N=0x01, 6> D=0x0989680 6> ] 6> D:\boost_1_52_0_beta1\boost/thread/win32/basic_timed_mutex.hpp(199) : see reference to function template instantiation 'To boost::chrono::ceil<boost::chrono::milliseconds,int_least64_t,boost::ratio<N,D>>(const boost::chrono::duration<Rep,Period> &)' being compiled 6> with 6> [ 6> To=boost::chrono::milliseconds, 6> N=0x01, 6> D=0x0989680, 6> Rep=int_least64_t, 6> Period=boost::ratio<0x01,0x0989680> 6> ]