FWIW the C++ standard actually prohibits CoW strings, and any C++ standard library that implements CoW strings is doing so in defiance of the standard. AIUI thi

FWIW the C++ standard actually prohibits CoW strings, and any C++ standard library that implements CoW strings is doing so in defiance of the standard. AIUI this prohibition was completely accidental, and I believe it's due to the rules around which string operations do and do not invalidate iterators.