Several similar warnings for each of... PRINT_ORDER(short); PRINT_ORDER(int); PRINT_ORDER(long); because the comparison in the "for" loop of print_byte_order() is comparing "i" of type T against the return of sizeof() which is unsigned... /home/jody/boost_1_32_0/libs/config/test/config_info.cpp: In function `void regex_lib_print_byte_order(const char*, T) [with T = short int]': /home/jody/boost_1_32_0/libs/config/test/config_info.cpp:723: instantiated from here /home/jody/boost_1_32_0/libs/config/test/config_info.cpp:74: warning: comparison between signed and unsigned integer expressions /home/jody/boost_1_32_0/libs/config/test/config_info.cpp:80: warning: comparison between signed and unsigned integer expressions /home/jody/boost_1_32_0/libs/config/test/config_info.cpp:84: warning: comparison between signed and unsigned integer expressions