kept it simple: ------------------------ #include <boost/regex.hpp> int main(int argc,char argv[]) { return 1; } --------- So all it does is try to compile the headers for the regex lib. Here is the output. ------------------------------ g++ -I/cy/f/Programs/development/boost_1_32_0/nocygwin/include/boost-1_32 -ansi -pedantic -Wall -O2 -c main.cpp -o main.o In file included from /cy/f/Programs/development/boost_1_32_0/nocygwin/include/boost-1_32/boost/regex/regex_traits.hpp:32, from /cy/f/Programs/development/boost_1_32_0/nocygwin/include/boost-1_32/boost/regex/v4/regex.hpp:57, from /cy/f/Programs/development/boost_1_32_0/nocygwin/include/boost-1_32/boost/regex.hpp:34, from main.cpp:1: /cy/f/Programs/development/boost_1_32_0/nocygwin/include/boost-1_32/boost/regex/v4/regex_traits.hpp:827: error: overflow in constant expression /cy/f/Programs/development/boost_1_32_0/nocygwin/include/boost-1_32/boost/regex/v4/regex_traits.hpp:840: error: overflow in constant expression -- Thad