Robert Ramey:
I've been reading the posts on this subject with interest. I don't have strong position myself. I do believe that some extra effort and/or risk is justified to get best performance. I'm leaving for you guys to do battle over the various alternatives. I strongly believe in const correctness and believe that things are "const" for a reason so I'm not enamored with a const_cast of any kind. I would much prefer a "guarenteed correct" solution if its close to best efficiency.
Hence I like the current suggestion. But does't it presume that s.begin() points to a real array which would be an implemenation feature?. That is, do I know that a standard conforming string is actually an array of adjacent characters?
The standard doesn't guarantee that a std::string is a contiguous array, but all existing implementations are. You can use &s[0] and take the risk, or you can prefer dispatching on whether s.begin() returns a pointer.