22 General utilities library [utilities]

Constraints:

• (1.1)
  sizeof(To) == sizeof(From) is true;
• (1.2)
  is_trivially_copyable_v<To> is true; and
• (1.3)
  is_trivially_copyable_v<From> is true.

Returns: An object of type To.

Implicitly creates objects nested within the result ([intro.object]).

Each bit of the value representation of the result is equal to the corresponding bit in the object representation of from.

Padding bits of the result are unspecified.

For the result and each object created within it, if there is no value of the object's type corresponding to the value representation produced, the behavior is undefined.

If there are multiple such values, which value is produced is unspecified.

A bit in the value representation of the result is indeterminate if it does not correspond to a bit in the value representation of from or corresponds to a bit for which the smallest enclosing object is not within its lifetime or has an indeterminate value ([basic.indet]).

A bit in the value representation of the result is erroneous if it corresponds to a bit for which the smallest enclosing object has an erroneous value.

For each bit b in the value representation of the result that is indeterminate or erroneous, let u be the smallest object containing that bit enclosing b:

• (2.1)
  If u is of unsigned ordinary character type or std​::​byte type, u has an indeterminate value if any of the bits in its value representation are indeterminate, or otherwise has an erroneous value.
• (2.2)
  Otherwise, if b is indeterminate, the behavior is undefined.
• (2.3)
  Otherwise, the behavior is erroneous, and the result is as specified above.

The result does not otherwise contain any indeterminate or erroneous values.

Remarks: This function is constexpr if and only if To, From, and the types of all subobjects of To and From are types T such that:

• (3.1)
  is_union_v<T> is false;
• (3.2)
  is_pointer_v<T> is false;
• (3.3)
  is_member_pointer_v<T> is false;
• (3.4)
  is_volatile_v<T> is false; and
• (3.5)
  T has no non-static data members of reference type.