From: Alexander Terekhov <terekhov@web.de>
Maxim Yegorushkin wrote: [...]
Here is the link: http://conststring.sourceforge.net/
"The mutability of std::basic_string<> and its interface do not allow implementers to make it a lightweight value object with cheap copy operation through string representation sharing and copy-on-write technique while maintaining thread safety."
This claim borders on blatant FUD. Claims to the extent that std:: string is sorta "less thread-safe then char[]" don't hold water because there isn't non-const overload of operator[] for char[].
I think it's just saying that COW can make strings more efficient in single-threaded applications, but it's a pessimization for multithreaded applications. Thus, an implementation can provide different versions of std::basic_string for ST versus MT builds, it can use COW (with locking for MT), or it can eschew COW altogether. The first choice is harder for the implementer, but results in (potentially) the best performance in both cases. The second is suboptimal in MT applications, and the third is suboptimal in ST applications. Using an immutable string ensures the best performance regardless of platform and threading model, even if that is the same as the performance of std::basic_string on select platform/threading model configurations. -- Rob Stewart stewart@sig.com Software Engineer http://www.sig.com Susquehanna International Group, LLP using std::disclaimer;