On 14 Nov 2013 at 0:04, Andrey Semashev wrote:
I don't like the idea of having two practically equivalent classes which basically do the same thing. The difference between the classes would be in the behavior, which is not specified by the standard in the first place and can be adjusted in a non-breaking manner in a unified boost::type_info class.
Taking off my peer review manager hat: I see there being a base boost::type_info class, with quirks adapters for backwards compatibility deriving from it. Such quirk adapters would be extremely thin (basically changing what name() does, and a few other minor changes). Regarding the standard's definition of type_info, that is unimportant here except where some boost::type_info_something is declared to behave exactly like std::type_info. If we explicitly declare that boost::type_info is intended as being superior to the standard and therefore a breaking change from it, I see no issue. Someone will now mention that because boost::type_info derives from std::type_info that one cannot safely change its API. And this was exactly my original point: a boost::type_info_something capable of directly substituting according to the C++ type rules for std::type_info MUST replicate as a minimum what the C++11 standard says AND what the local implementation std::type_info does, including quirks. Otherwise you get the problem that one compiland using std::type_info will segfault when it encounters a boost::type_info from another compiland which has been auto-converted to std::type_info by the compiler. Quite separately from this is where the programmer intentionally replaces std::type_info with boost::type_info and the program compiles and executes correctly because boost::type_info has been cleverly designed to do so AND the programmer understands what that means. That's a compile-time compatible type_info, which is very different from a run-time compatible type_info. Putting back on my peer review manager hat, I'd like to thank the list for such a useful debate. It's certainly helped me see aspects of the library I had not previously considered. I'll try to produce an interim report this weekend to help frame the discussion during the last five days of review. Niall -- Currently unemployed and looking for work. Work Portfolio: http://careers.stackoverflow.com/nialldouglas/