[meta.reflection.layout]

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struct member_offset {
  ptrdiff_t bytes;
  ptrdiff_t bits;
  constexpr ptrdiff_t total_bits() const;
  auto operator<=>(const member_offset&) const = default;
};

constexpr ptrdiff_t member_offset::total_bits() const;

Returns: bytes * CHAR_BIT + bits.

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consteval member_offset offset_of(info r);

Let V be the offset in bits from the beginning of a complete object of the type represented by parent_of(r) to the subobject associated with the construct represented by r.

Throws: meta::exception unless r represents a non-static data member, unnamed bit-field, or direct base class relationship

(D, B) for which either B is not a virtual base class or D is not an abstract class .

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consteval size_t size_of(info r);

Returns: If

(5.1)
r represents a non-static data member of type T or a data member description $(T, N, A, W, N U A) or$
(5.2)
dealias(r) represents a type T,

then sizeof(T) if T is not a reference type and size_of(add_pointer(^^T) otherwise.

Otherwise, size_of(type_of(r)).

[Note 1:

It is possible that while sizeof(char) == size_of(^char) is true, that sizeof(char&) == size_of(^^char&) is false.

If b represents a direct base class relationship of an empty base class, then size_of(b) > 0 is true.

— end note]

Throws: meta::exception unless all of the following conditions are met:

(6.1)
dealias(r) is a reflection of a type, object, value, variable of non-reference type, non-static data member that is not a bit-field, direct base class relationship, or data member description $(T, N, A, W, N U A) ([class. mem. general]) where W is ⊥ .$
(6.2)
If dealias(r) represents a type, then is_complete_type(r) is true.

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consteval size_t alignment_of(info r);

Returns:

(7.1)
If dealias(r) represents a type T, then alignment_of(add_pointer(r)) if T is a reference type and the alignment requirement of T otherwise.
(7.2)
Otherwise, if dealias(r) represents a variable or object, then the alignment requirement of the variable or object.
(7.3)
Otherwise, if r represents a direct base class relationship, then alignment_of(type_of(r)).
(7.4)
Otherwise, if r represents a non-static data member M of a class C, then the alignment of the direct member subobject corresponding to M of a complete object of type C.
(7.5)
Otherwise, r represents a data member description $(T, N, A, W, N U A) ([class. mem. general]) .$

If A is not ⊥, then the value A.

Otherwise, alignment_of(^T).

Throws: meta::exception unless all of the following conditions are met:

(8.1)
dealias(r) is a reflection of a type, object, variable of non-reference type, non-static data member that is not a bit-field, direct base class relationship, or data member description $(T, N, A, W, N U A) ([class. mem. general]) where W is ⊥ .$
(8.2)
If dealias(r) represents a type, then is_complete_type(r) is true.

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consteval size_t bit_size_of(info r);

Returns:

(9.1)
If r represents an unnamed bit-field or a non-static data member that is a bit-field with width W, then W.
(9.2)
Otherwise, if r represents a data member description $(T, N, A, W, N U A) ([class. mem. general]) and W is not ⊥, then W .$
(9.3)
Otherwise, CHAR_BIT * size_of(r).

Throws: meta::exception unless all of the following conditions are met:

(10.1)
dealias(r) is a reflection of a type, object, value, variable of non-reference type, non-static data member, unnamed bit-field, direct base class relationship, or data member description.
(10.2)
If dealias(r) represents a type, then is_complete_type(r) is true.

21 Metaprogramming library [meta]

21.4 Reflection [meta.reflection]

21.4.11 Reflection layout queries [meta.reflection.layout]