i've been using the regex library fine to match patterns, but when i changed my objects so the regex object is stored instead of initialised each time, i get linking problems. basically it was working fine as: (simplified code): bool myclass::myfunction(char* testString) { regex mypattern("abcd"); cmatch result; return regex_match(testString, result, mypattern); } but when i changed it to store the mypattern object it came up with linker problems: class myclass { ... regex _mypattern; } void myclass::myclass() { _mypattern = regex("abcd"); } bool myfunction(char* testString) { cmatch result; return regex_match(testString, result, _mypattern); } the complaint seems to be about the copy constructor and op= methods, which are supposedly implemented in the boost_regex library. i'm linking using -lboost_regex-mgw (with the library path defined in LIBRARY_PATH); Anthony