Cast raw bytes to any datatype

Question

I'm worried if my implementation is unsafe or could be improved. Suppose I have an array of bytes (more specifically, std::byte); is casting an element's address to a void pointer and then to any datatype safe?

template <typename To>
constexpr To *byte_cast(std::byte &From) {
  return static_cast<To *>(static_cast<void *>(&From));
}

// or rather
template <typename To>
constexpr To *byte_cast(std::byte *From) {
  return static_cast<To *>(static_cast<void *>(From));
}

I'm avoiding reinterpret_cast due to its unreliability. Do note that I want to the T * to keep same address of the byte it was cast from.

I do have in mind that the array might not fit the datatype, or maybe endianness might cause a problem, but both will be fixed after my question's answered.

Answer 1

Your paired static_casts are exactly equivalent to a reinterpret_cast. Both cause UB due to strict aliasing violations (except when the target type is char, unsigned char, or std::byte).

The solution is std::bitcast<T>(source). It has the interface similar to what you attempted, except that it returns by value. It's not possible to have a "safe reinterpret_cast" that would return a pointer/reference.

A less modern alternative is std::memcpy.