如何计算C结构中的填充

Question

While I understand how padding generally works in a C struct, I struggle to understand how inner struct are padded. Example:

struct inner
{
    int a;
}

struct outer
{
   char a;
   struct inner b;
}

How is the padding between member outer.a and member outer.b calculated?

How is the padding of the end of struct outer calculate when the data type of member inner.a changes from int to short or double ?

What are the implications of calculating these paddings in a 32 bit architecture versus a 64 bit one?

Answer 1

I always find it better to hex-dump such things and play around in order to understand better. Here is an example for your case:

example