[scoutt]

If you declare a structure of unaligned size, the compiler might (probably must) introduce some padding bytes at the end of the structure to fit the alignment. In some architectures you cannot do unaligned accesses (ARM for example).

Unless you pack the structure with the alignment you want.

[wmkn]

Yes, so the structure itself has padding (added by the compiler). But that is regardless of whether it is in an array or not. OP seemed to suggest that C arrays introduce padding of some sort, which they do not.