A solution used in the Linux kernel[0] is to use a struct with the packed attribute, which implies the fields aren't necessarily aligned. Simplifying, I think this macro should work the same in gcc and similar: apply to any pointer to get something that behaves as *p but will read or write as unaligned.

    #define unaligned(P) (((struct { typeof(*(P)) x; } __attribute__((packed))*)(P))->x)

[0] https://github.com/torvalds/linux/blob/7b9e664beb237d90bc600...