On Wed, May 15, 2024 at 7:58 AM Jonathan Wakely wrote:
>
> Why would you want to hash the indeterminate padding
> bits between members anyway?


How about we add a new constexpr function to the standard library
called "std::zero_padding":

    template<typename T> requires (!is_const_v< remove_reference_t<T> >)
    constexpr T &&zero_padding(T &&obj, bool const skip_tail = false)
    {
        // Step 1: Zero out the padding bits inside integer types
        // Step 2: Zero out the padding bytes between member variables
        // Step 3: If 'skip_tail' is false, zero out the tail padding
        // (must set to 'true' when used with 'no_unique_address')
    }

With regard to Step 1, this is a throw back to the days when a 36-Bit
integer was a 32-Bit integer with 4 padding bits -- so probably
doesn't apply today.

The hash algorithm could hash "__datasizeof(T)" instead of
"sizeof(T)", which is why in the above function I give the option of
skipping the tail padding.