Exceptions

Sometimes classes must provide access to internal handles for compatibility reasons, such as interfacing with legacy code or other systems. For example, std::basic_string offers access to its internal handle via the data and the c_str member functions for compatibility with functions that expect C-style pointersbut that presumably do not store those pointers or try to write through them! Such backdoor access functions are a necessary evil that should be used rarely and cautiously, and the conditions under which the handle remains valid must be carefully documented.