TYPE_NEEDS_CONSTRUCTING zero for std::string?

[Florian Weimer]

* Martin Sebor via Gcc:

> I'd expect TYPE_NEEDS_CONSTRUCTING to be non-zero in the middle end
> for any C++ type with a user-defined ctor, but in some of my testing
> I see it's actually zero for std::string, at least in some instances
> (but nonzero for other types with ctors).  Is there something special
> about std::string that makes it so?  (If this is intentional, how can
> I create my own type that has a user-defined ctor and also a zero
> TYPE_NEEDS_CONSTRUCTING?)

I assume by writing an explicit default constructor:

  T() = default;

Thanks,
Florian