Sample program: ---%<--- #include <limits> #include <iostream> using namespace std; int main() { cout << numeric_limits<long long>::is_specialized << '\n'; cout << numeric_limits<unsigned long long>::is_specialized << '\n'; } --->%--- Compiling and running this on Tru64/CXX with relaxed ANSI mode gives: schoepf@area51:~/net/tmp> cxx -version V6.5-042 -O0 -std ansi -model ansi ./test_ll_limits.cpp && ./a.out 1 1 Compiling and running this on Tru64/CXX with strict ANSI mode gives: schoepf@area51:~/net/tmp> cxx -version V6.5-042 -O0 -std strict_ansi -model ansi ./test_ll_limits.cpp && ./a.out cxx: Warning: ./test_ll_limits.cpp, line 8: the type "long long" is nonstandard cout << numeric_limits<long long>::is_specialized << '\n'; ------------------------------^ cxx: Warning: ./test_ll_limits.cpp, line 9: the type "long long" is nonstandard cout << numeric_limits<unsigned long long>::is_specialized << '\n'; ---------------------------------------^ 0 0 But when running configure in libs/config with CXX="cxx -version V6.5-042 -std strict_ansi -model ansi" bash ./configure, BOOST_NO_LONG_LONG_NUMERIC_LIMITS doesn't get defined in the resulting "user.hpp". The relevant section from the log file looks like this: configure:2190: checking std::numeric_limits<long long> configure:2220: cxx -version V6.5-042 -std strict_ansi -model ansi -o conftest -I./../.. -I./../../libs/config/test -g -DBOOST_NO_CONFIG conftest.cpp -lrt -lm >&5 configure:2223: $? = 0 Why does configure think that the specializations are present? Markus