// <experimental/any> -*- C++ -*-
-// Copyright (C) 2014-2019 Free Software Foundation, Inc.
+// Copyright (C) 2014-2020 Free Software Foundation, Inc.
//
// This file is part of the GNU ISO C++ Library. This library is free
// software; you can redistribute it and/or modify it under the
/** @file experimental/any
* This is a TS C++ Library header.
+ * @ingroup libfund-ts
*/
#ifndef _GLIBCXX_EXPERIMENTAL_ANY
{
/**
* @defgroup any Type-safe container of any type
- * @ingroup experimental
+ * @ingroup libfund-ts
*
* A type-safe container for single values of value types, as
* described in n3804 "Any Library Proposal (Revision 3)".
virtual const char* what() const noexcept { return "bad any_cast"; }
};
+ /// @cond undocumented
[[gnu::noreturn]] inline void __throw_bad_any_cast()
{
#if __cpp_exceptions
__builtin_abort();
#endif
}
+ /// @endcond
/**
* @brief A type-safe container of any type.
// observers
/// Reports whether there is a contained object or not.
- bool empty() const noexcept { return _M_manager == nullptr; }
+ _GLIBCXX_NODISCARD bool empty() const noexcept { return _M_manager == nullptr; }
#if __cpp_rtti
/// The @c typeid of the contained object, or @c typeid(void) if empty.
_Storage _M_storage;
template<typename _Tp>
- friend void* __any_caster(const any* __any);
+ friend enable_if_t<is_object<_Tp>::value, void*>
+ __any_caster(const any* __any);
// Manage in-place contained object.
template<typename _Tp>
}
// @}
+ /// @cond undocumented
template<typename _Tp>
- void* __any_caster(const any* __any)
+ enable_if_t<is_object<_Tp>::value, void*>
+ __any_caster(const any* __any)
{
- struct _None { };
- using _Up = decay_t<_Tp>;
- using _Vp = conditional_t<is_copy_constructible<_Up>::value, _Up, _None>;
- if (__any->_M_manager != &any::_Manager<_Vp>::_S_manage)
- return nullptr;
- any::_Arg __arg;
- __any->_M_manager(any::_Op_access, __any, &__arg);
- return __arg._M_obj;
+ // any_cast<T> returns non-null if __any->type() == typeid(T) and
+ // typeid(T) ignores cv-qualifiers so remove them:
+ using _Up = remove_cv_t<_Tp>;
+ // The contained value has a decayed type, so if decay_t<U> is not U,
+ // then it's not possible to have a contained value of type U.
+ using __does_not_decay = is_same<decay_t<_Up>, _Up>;
+ // Only copy constructible types can be used for contained values.
+ using __is_copyable = is_copy_constructible<_Up>;
+ // If the type _Tp could never be stored in an any we don't want to
+ // instantiate _Manager<_Tp>, so use _Manager<any::_Op> instead, which
+ // is explicitly specialized and has a no-op _S_manage function.
+ using _Vp = conditional_t<__and_<__does_not_decay, __is_copyable>::value,
+ _Up, any::_Op>;
+ // First try comparing function addresses, which works without RTTI
+ if (__any->_M_manager == &any::_Manager<_Vp>::_S_manage
+#if __cpp_rtti
+ || __any->type() == typeid(_Tp)
+#endif
+ )
+ {
+ any::_Arg __arg;
+ __any->_M_manager(any::_Op_access, __any, &__arg);
+ return __arg._M_obj;
+ }
+ return nullptr;
}
+ // This overload exists so that std::any_cast<void(*)()>(a) is well-formed.
+ template<typename _Tp>
+ enable_if_t<!is_object<_Tp>::value, _Tp*>
+ __any_caster(const any*) noexcept
+ { return nullptr; }
+ /// @endcond
+
/**
* @brief Access the contained object.
*
}
}
+ // Dummy specialization used by __any_caster.
+ template<>
+ struct any::_Manager_internal<any::_Op>
+ {
+ static void
+ _S_manage(_Op, const any*, _Arg*) { }
+ };
+
// @} group any
} // namespace fundamentals_v1
} // namespace experimental