Why can you assign nullptr to std::string?

Question

So today I wrote a fairly hard to find bug where I initialized a std::string to nullptr (not a pointer to std::string, but the value itself). I\'ve found apparently it\'s on

Answer 1

That's simply because there are constructors (number (5) in the link) and assignment operators (number (3) in the link) for std::string that accept a const char*, and hence the nullptr matches.

Before C++11 (and therefore before nullptr), the same problem occurred when you tried to construct from 0 or NULL. All those cases were illegal and result in undefined behaviour, although at least one STL (RogueWave?) accepted it in the past and generated an empty string.