bsl::is_empty

Meta‐function for detecting empty class types.

Synopsis

Declared in <bslmf_isempty.h>

template<class t_TYPE>
struct is_empty
    : bsl::integral_constant<bool, ::std::is_empty<t_TYPE>::value>

Description

This struct is a meta‐function to determine whether the (template parameter) t_TYPE is an empty class type. This struct derives from bsl::true_type if the t_TYPE is empty, and from bsl::false_type otherwise. This meta‐function has the same syntax as the is_empty meta‐function defined in the C++11 standard [meta.unary.prop]; on C++03 platforms, however, this meta‐function defaults to true_type if t_TYPE is a class or struct with no non‐static data members other than bit‐fields of length 0, no virtual member functions, no virtual base classes, and no base class B for which is_empty<B>::value is false; otherwise is_empty defaults to false_type. Note that this meta‐function will fail to compile for a union that is the same size as an empty class in C++03.