std::is_pointer_interconvertible_with_class - cppreference.com (original) (raw)
| | | | | --------------------------------------------------------------------------------------------------------------- | | ------------- | | template< class S, class M > constexpr bool is_pointer_interconvertible_with_class( M S::* mp ) noexcept; | | (since C++20) |
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.
[edit] Parameters
| mp | - | a pointer-to-member to detect |
|---|
[edit] 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.
[edit] 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 | Value | Std | Feature |
|---|---|---|---|
| __cpp_lib_is_pointer_interconvertible | 201907L | (C++20) | Pointer-interconvertibility traits: std::is_pointer_interconvertible_base_of, std::is_pointer_interconvertible_with_class |
[edit] Example
#include struct Foo { int x; }; struct Bar { int y; }; struct Baz : Foo, Bar {}; // not standard-layout static_assert( not std::is_same_v<decltype(&Baz::x), int Baz::*> ); static_assert( std::is_pointer_interconvertible_with_class(&Baz::x) ); static_assert( not std::is_pointer_interconvertible_with_class<Baz, int>(&Baz::x) ); int main() { }