Core dump constructing a C++ string with NULL

[Ian Lance Taylor]

Tom Browder <tom.browder@gmail.com> writes:

> It would be nice if this would construct an empty string:
>
>   #include <string>
>   std::string s(0);
>
> At the moment that gives a core dump.
>
> Is that defined behavior according to the standard?  If not, what
> about a g++ enhancement?

The standard says that you may only pass a valid pointer to the
std::string constructor.  You are passing an invalid pointer, so your
code is undefined.

As to whether libstdc++ should check for NULL, that is a perennial
question: should we slow down the library a tiny bit for everybody in
order to do better handling of an undefined case for those who find it
more convenient?  There is no clearly correct answer.

Ian