Hmm, I don't understand (sorry). The pointer to the internal array must be aligned. But how does the element size play into the padding. If we take these two examples?

   [repr(C)]
   struct StructA
   {
      pub foo: f32,
      _alignment: [SixteenBytes, 0]
   }

   [repr(C)]
   struct StructB
   {
      pub foo: f32,
      _alignment: [ThirtytwoBytes, 0]
   }

Are both just padded with 16-4 and 32-4 bytes respectively, so they are equivalent to making a padding like this in the first case?

   [repr(C)]
   struct StructAPadded
   {
      pub foo: f32,
      _padding : TwelveBytes;
   }