This little snippet complies fine with the /Ze switch which enables Microsoft extensions #include <boost/integer.hpp> int main(){ return 0; } But if you disable microsoft extensions with the /Za switch then you get the following errors mess of errors. 1>c:\boost\include\boost-1_40\boost\integer_fwd.hpp(70) : error C2039: 'long_long_type' : is not a member of 'boost' 1>c:\boost\include\boost-1_40\boost\integer_fwd.hpp(70) : error C2065: 'long_long_type' : undeclared identifier 1>c:\boost\include\boost-1_40\boost\integer_fwd.hpp(70) : error C2913: explicit specialization; 'boost::integer_traits' is not a specialization of a class template 1>c:\boost\include\boost-1_40\boost\integer_fwd.hpp(73) : error C2913: explicit specialization; 'boost::integer_traits' is not a specialization of a class template 1>c:\boost\include\boost-1_40\boost\integer_traits.hpp(67) : error C2913: explicit specialization; 'boost::integer_traits' is not a specialization of a class template 1>c:\boost\include\boost-1_40\boost\integer_traits.hpp(73) : error C2913: explicit specialization; 'boost::integer_traits' is not a specialization of a class template 1>c:\boost\include\boost-1_40\boost\integer_traits.hpp(79) : error C2913: explicit specialization; 'boost::integer_traits' is not a specialization of a class template 1>c:\boost\include\boost-1_40\boost\integer_traits.hpp(85) : error C2913: explicit specialization; 'boost::integer_traits' is not a specialization of a class template 1>c:\boost\include\boost-1_40\boost\integer_traits.hpp(119) : error C2913: explicit specialization; 'boost::integer_traits' is not a specialization of a class template 1>c:\boost\include\boost-1_40\boost\integer_traits.hpp(126) : error C2913: explicit specialization; 'boost::integer_traits' is not a specialization of a class template 1>c:\boost\include\boost-1_40\boost\integer_traits.hpp(132) : error C2913: explicit specialization; 'boost::integer_traits' is not a specialization of a class template 1>c:\boost\include\boost-1_40\boost\integer_traits.hpp(138) : error C2913: explicit specialization; 'boost::integer_traits' is not a specialization of a class template 1>c:\boost\include\boost-1_40\boost\integer_traits.hpp(144) : error C2913: explicit specialization; 'boost::integer_traits' is not a specialization of a class template 1>c:\boost\include\boost-1_40\boost\integer_traits.hpp(150) : error C2913: explicit specialization; 'boost::integer_traits' is not a specialization of a class template 1>c:\boost\include\boost-1_40\boost\integer_traits.hpp(156) : error C2913: explicit specialization; 'boost::integer_traits' is not a specialization of a class template 1>c:\boost\include\boost-1_40\boost\integer.hpp(88) : error C2065: 'const_max' : undeclared identifier 1> c:\boost\include\boost-1_40\boost\integer.hpp(94) : see reference to class template instantiation 'boost::int_max_value_t<MaxValue>' being compiled 1>c:\boost\include\boost-1_40\boost\integer.hpp(89) : error C2065: 'const_max' : undeclared identifier 1>c:\boost\include\boost-1_40\boost\integer.hpp(90) : error C2065: 'const_max' : undeclared identifier 1>c:\boost\include\boost-1_40\boost\integer.hpp(91) : error C2065: 'const_max' : undeclared identifier 1>c:\boost\include\boost-1_40\boost\integer.hpp(101) : error C2065: 'const_min' : undeclared identifier 1> c:\boost\include\boost-1_40\boost\integer.hpp(107) : see reference to class template instantiation 'boost::int_min_value_t<MinValue>' being compiled 1>c:\boost\include\boost-1_40\boost\integer.hpp(102) : error C2065: 'const_min' : undeclared identifier 1>c:\boost\include\boost-1_40\boost\integer.hpp(103) : error C2065: 'const_min' : undeclared identifier 1>c:\boost\include\boost-1_40\boost\integer.hpp(104) : error C2065: 'const_min' : undeclared identifier 1>c:\boost\include\boost-1_40\boost\integer.hpp(116) : error C2065: 'const_max' : undeclared identifier 1> c:\boost\include\boost-1_40\boost\integer.hpp(122) : see reference to class template instantiation 'boost::uint_value_t<Value>' being compiled 1>c:\boost\include\boost-1_40\boost\integer.hpp(117) : error C2065: 'const_max' : undeclared identifier 1>c:\boost\include\boost-1_40\boost\integer.hpp(118) : error C2065: 'const_max' : undeclared identifier 1>c:\boost\include\boost-1_40\boost\integer.hpp(119) : error C2065: 'const_max' : undeclared identifier