C语言结构的成员对齐

Natural Alignment == sizeof(type);
  Order  Alignment ==  k == 所指定的Alignment; 例如#pragma pack(8) k == 8;
  Actual Alignment == min(Natural Alignment, k);
  struct Actual Alignment == max(each member);
  sizeof(struct) == n * struct Actual Alignment; 不够要加padding
  
  所谓对齐就是此成员所在 基地址%Actual Align 必须为0