public member function
nested_exception (const nested_exception& e) noexcept = default;
Constructs a nested_exception object.
The default constructor (1) stores in the object an exception_ptr that points to the currently handled exception, as returned by current_exception. If no exception is being handled, the object stores a null exception_ptr.
The copy constructor (2) is explicitly defaulted.
No-throw guarantee: this member function never throws exceptions.