/fs/tools/L1/boost_1_43_0/boost/asio/error.hpp: At global scope: /fs/tools/L1/boost_1_43_0/boost/asio/error.hpp:353: warning: 'boost::asio::error::system_category' defined but not used /fs/tools/L1/boost_1_43_0/boost/asio/error.hpp:355: warning: 'boost::asio::error::netdb_category' defined but not used /fs/tools/L1/boost_1_43_0/boost/asio/error.hpp:357: warning: 'boost::asio::error::addrinfo_category' defined but not used /fs/tools/L1/boost_1_43_0/boost/asio/error.hpp:359: warning: 'boost::asio::error::misc_category' defined but not used /fs/tools/L1/boost_1_43_0/boost/asio/error.hpp:361: warning: 'boost::asio::error::ssl_category' defined but not used /fs/tools/L1/boost_1_43_0/boost/system/error_code.hpp:208: warning: 'boost::system::system_category' defined but not used /fs/tools/L1/boost_1_43_0/boost/system/error_code.hpp:209: warning: 'boost::system::generic_category' defined but not used /fs/tools/L1/boost_1_43_0/boost/system/error_code.hpp:214: warning: 'boost::system::posix_category' defined but not used /fs/tools/L1/boost_1_43_0/boost/system/error_code.hpp:215: warning: 'boost::system::errno_ecat' defined but not used /fs/tools/L1/boost_1_43_0/boost/system/error_code.hpp:216: warning: 'boost::system::native_ecat' defined but not used Code defines static variables in header which is bad form. static const boost::system::error_category& system_category = boost::asio::error::get_system_category(); In gcc the warning could be disabled with -Wno-unused-variable, but that disables valuable warnings. Are these variables really needed? They theoretically create a word per compilation scope. A cleaner alternative would be to just call the function where needed. If you really need to define global variables in a header only library, you can define static members of a template class. It's a fancy trick (not sure if it has a name). Perhaps there are portablity issues with it. Chris