Re: decltype

[Jonathan Wakely <jwakely.gcc@gmail.com>]

This question is not about GCC so would be more appropriate in a
general C++ forum, e.g. stackoverflow.com


On 25 February 2014 15:46, Graziano Servizi wrote:
> Could you kindly explain to me how and when the decltype keyword do have a
> tilde character prefixed?
> I'm unable to figure out the cases in which such a syntax would be used and
> I found it as an example of an "id-expression" together with the name of a
> destructor: should be to explicitly call a destructor of some class?

Yes, it's used in a pseudo-destructor call.

For example, to destroy an object returned by a function:

template<typename Func>
void foo(Func f)
{
  auto obj = f();
  obj.~decltype(obj)();
}

This is equivalent to:

template<typename Func>
void foo(Func f)
{
  auto obj = f();
  using Object = decltype(obj);
  obj.~Object();
}

This syntax is very rarely needed.