k i have program a.h that uses boost filesystem. b.h includes a.h and also uses boost::filesystem.. when i build i get this error. C:/Boost/include/boost_1_34/boost/filesystem/convenience.hpp:70: multiple defini tion of `boost::filesystem::basename(boost::filesystem::basic_path<std::string, boost::filesystem::path_traits> const&)' ./teng/lib/libmy.a(my.o):C:/Boost/include/boost_1_34/boost/filesys tem/convenience.hpp:70: first defined here ./teng/lib/libmy.a(my2.o): In function `ZN5boost10filesystem9exten sionERKNS0_10basic_pathISsNS0_11path_traitsEEE': C:/Boost/include/boost_1_34/boost/filesystem/convenience.hpp:58: multiple defini tion of `boost::filesystem::extension(boost::filesystem::basic_path<std::string, boost::filesystem::path_traits> const&)' ./teng/lib/libmy.a(my.o):C:/Boost/include/boost_1_34/boost/filesys tem/convenience.hpp:58: first defined here