Debugging of code operating with mid-weight and heavy strings under Visual C++ is a real pain. Visual C++ native debugger has no cunning mechanism to show long strings. Of course, there are some debugger symbols like "s" and "su" which allow to see at most 252 symbols of string. But what about the rest?
StringWatch add-in gives You the possibility to view the whole string. The length doesn't matter. Add-in even can detect the type of string: multi-byte or Unicode, CString or std::basic_string, _bstr_t or CComBSTR. The only slowdown can be caused by edit control. SetDlgItemText() takes to much time to output long strings to edit.
Here you can get more information about add-in and get the latest version.