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std::is_pointer_interconvertible_with_class(3) | C++ Standard Libary | std::is_pointer_interconvertible_with_class(3) |
NAME¶
std::is_pointer_interconvertible_with_class - std::is_pointer_interconvertible_with_class
Synopsis¶
Defined in header <type_traits>
template<class S, class M>
constexpr bool is_pointer_interconvertible_with_class( M S::* mp ) (since
C++20)
noexcept;
Given an object s of type S, determines whether s.*mp refers to a subobject
of s and
s is pointer-interconvertible with its subobject s.*mp. The program is
ill-formed if
S is not a complete type.
If S is not a StandardLayoutType, or M is not an object type, or mp is equal
to
nullptr, the result is always false.
Parameters¶
mp - a pointer-to-member to detect
Return value¶
true if s.*mp refers a subobject of s and s is
pointer-interconvertible with its
subobject s.*mp, otherwise false, where s is an object of type S.
Notes¶
The type of a pointer-to-member expression &S::m is not
always M S::*, where m is of
type M, because m may be a member inherited from a base class of S. The
template
arguments can be specified in order to avoid potentially surprising
results.
If there is a value mp of type M S::* such that
std::is_pointer_interconvertible_with_class(mp) == true, then
reinterpret_cast<M&>(s) has well-defined result and it refers the
same subobject as
s.*mp, where s is a valid lvalue of type S.
On common platforms, the bit pattern of mp is all zero if
std::is_pointer_interconvertible_with_class(mp) == true.
Feature-test macro: __cpp_lib_is_pointer_interconvertible
Example¶
// Run this code
#include <type_traits>
#include <iostream>
struct Foo { int x; };
struct Bar { int y; };
struct Baz : Foo, Bar {}; // not standard-layout
int main()
{
std::cout << std::boolalpha
<< std::is_same_v<decltype(&Baz::x), int Baz::*> <<
'\n'
<< std::is_pointer_interconvertible_with_class(&Baz::x) <<
'\n'
<< std::is_pointer_interconvertible_with_class<Baz,
int>(&Baz::x) << '\n';
}
Output:¶
false
true
false
See also¶
is_standard_layout checks if a type is a standard-layout type
(C++11) (class template)
is_member_object_pointer checks if a type is a pointer to a non-static member
object
(C++11) (class template)
2022.07.31 | http://cppreference.com |