Hi, I am using boost 1.37 on osx from macports and I have a problem using the regex library with gcc 4.4, although it seems to work perfectly with gcc 4.3 and 4.2. The problem is with creating a boost::regex object- simple program below: #include <boost/regex.hpp> #include <string> int main(int argc, char **argv) { std::string s("(.*)bar|(.*)bah"); boost::regex re_node(s); return 1; } The backtrace it produces is below: (gdb) bt #0 0x90d90b9e in __kill () #1 0x90d90b91 in kill$UNIX2003 () #2 0x90e07ec2 in raise () #3 0x90e1747f in abort () #4 0x0026792c in __gnu_cxx::__verbose_terminate_handler () #5 0x00265239 in __cxxabiv1::__terminate () #6 0x0026527d in std::terminate () #7 0x0026539c in __cxa_throw () #8 0x001eeb00 in std::__throw_bad_cast () #9 0x00370d25 in std::use_facet<std::messages<char> > () #10 0x00127c93 in boost::re_detail::cpp_regex_traits_base<char>::imbue () at cpp_regex_traits.hpp:215 #11 regex_data [inlined] () at basic_regex.hpp:173 #12 basic_regex_implementation (this=0x500200) at cpp_regex_traits.hpp:93 #13 0x001256a6 in shared_ptr<boost::re_detail::basic_regex_implementation<char, boost::regex_traits<char, boost::cpp_regex_traits<char> > > > [inlined] () at shared_ptr.hpp:525 #14 boost::basic_regex<char, boost::regex_traits<char, boost::cpp_regex_traits<char> > >::do_assign (this=0xbfffe790, p1=0x5001ec "(.*)bar|(.*)bah", p2=0x5001fb "", f=0) at basic_regex.hpp:525 #15 0x00001d6a in boost::basic_regex<char, boost::regex_traits<char, boost::cpp_regex_traits<char> > >::assign () #16 0x00001d3e in boost::basic_regex<char, boost::regex_traits<char, boost::cpp_regex_traits<char> > >::assign<std::char_traits<char>, std::allocator<char> > () #17 0x00001c9f in boost::basic_regex<char, boost::regex_traits<char, boost::cpp_regex_traits<char> > >::basic_regex<std::char_traits<char>, std::allocator<char> > () #18 0x00001b20 in main () (gdb) Is this a problem with boost, or with the compiler? Any ideas for a fix? many thanks, a