Here is another solution for loading a potentially unaligned 64-bit integer in the CPU's byte order, that does not violate strict aliasing: uint64_t load64(u

Here is another solution for loading a potentially unaligned 64-bit integer in the CPU's byte order, that does not violate strict aliasing: uint64_t load64(uint8_t const *b) { union { uint64_t u64; uint8_t u8[8]; } u = {.u8 = { b[0], b[1], b[2], b[3], b[4], b[5], b[6], b[7] }}; return u.u64; } Type punning through a union is explicitly supported by the C standard, insofar as we do not evaluate uninitialized memory or trap representations. We are fine here, as uint64_t has no trap representations, and must have exactly the size of 8 uint8_ts, as those types have no padding bits. GCC appears to compile this function to a plain unaligned load at optimization level 2, when supported, e.g. on arm64 (see https://godbolt.org/z/frEox67sG https://godbolt.org/z/frEox67sG).