ARM, RISC-V контроллеры

http://www.keil.com/support/man/docs/armcc/armcc_chr1359124990875.htm

Taking the address of a field in a #pragma packed struct does not yield a __packed pointer, so the compiler does not produce an error if you assign this address to a non-__packed pointer. However, the field might not be properly aligned for its type, and dereferencing such an unaligned pointer results in undefined behavior.

Кто бы мог подумать, RTFM.