Ticket #7278 asks that Boost.System add C++11 noexcept support. A reasonable request, and I implemented it this morning by adding BOOST_NOEXCEPT at the appropriate places specified in the standard. But there is a problem. noexcept is viral, so any classes that inherit from a class that uses noexcept must be changed to also use no except. An example: Boost.Filesystem has this class: class codecvt_error_cat : public boost::system::error_category { public: codecvt_error_cat(){} const char* name() const {return "codecvt";} std::string message(int ev) const; }; Compiling with GCC 4.7 -std=c++0x results in this error: ..\..\../boost/system/error_code.hpp:187:32: error: overriding 'virtual const char* boost::system::error_category::name() const noexcept (true)' To fix it, the filesystem class has to be changed: class codecvt_error_cat : public boost::system::error_category { public: codecvt_error_cat(){} const char* name() const BOOST_NOEXCEPT {return "codecvt";} std::string message(int ev) const; }; I've held off committing the Boost.System changes to trunk until we've had a chance to discuss how to approach this potential break to an unknown number of Boost and user libraries. Ideas? --Beman