This is mainly for the benefit of Google, but here's the full run-down on the /analyse warnings and their fixes: h:\source code\boost\boost_1_33_1\libs\regex\src\wide_posix_api.cpp(159) : warning C6200: Index '20' is out of valid index range '0' to '15' for non-stack buffer 'wchar_t const * * boost::`anonymous namespace'::wnames' It's a bug, it only strikes if you use regerr with the flags REG_ITOA or REG_ATOI set: these are debugging helpers added for compatibility with the BSD regex package, POSIX conforming code is not effected. The bug appears to have been present for several releases without anyone reporting it, so maybe I should have just removed that code (!), however fixes and enhanced test cases are in the diffs below. Frankly this one is embarrassing. h:\source code\boost\boost_1_33_1\boost\regex\v4\basic_regex_creator.hpp(1183) : warning C6297: Arithmetic overflow: 32-bit value is shifted, then cast to 64-bit value. Results might not be an expected value Another bug, but only strikes in certain rare situations when you have more than 32 repetition operators in the expression (that's not the only requirement though). Test cases and fix in the diffs below. h:\source code\boost\boost_1_33_1\boost\regex\v4\basic_regex_creator.hpp(1203) : warning C6297: Arithmetic overflow: 32-bit value is shifted, then cast to 64-bit value. Results might not be an expected value As above. h:\source code\boost\boost_1_33_1\boost\regex\v4\w32_regex_traits.hpp(537) : warning C6385: Invalid data: accessing 'unsigned long const * const `private: unsigned long __thiscall boost::re_detail::w32_regex_traits_implementation<char>::lookup_classname_imp(char const *,char const *)const '::`2'::masks', the readable size is '80' bytes, but '84' bytes might be read: Lines: 505, 528, 530, 531, 532, 535, 536, 537 I can't understand this one, in fact I'm certain it's not a bug :-) George: if you add an extra 0 to the data-array does that suppress the warning, or just shift it? I have a suspicion the analyser is getting confused by the +1 added to the index (this is correct the original value is in the range [-1, max-1), so does need to be shifted by one). h:\source code\boost\boost_1_33_1\boost\regex\v4\basic_regex_creator.hpp(576) : warning C6246: Local declaration of 'c3' hides declaration of the same name in outer scope. For additional information, see previous declaration at line '565' of 'h:\source code\boost\boost_1_33_1\boost\regex\v4\basic_regex_creator.hpp': Lines: 565 Basically harmless, but fixed anyway. HTH, John.