loadUnaligned and strict aliasing

[jj683]

Is folly::loadUnaligned function correct in terms of strict-aliasing rules?

A minimal example that reproduces undefined behavior:

#include <iostream>

#include <folly/Bits.h>

uint16_t checksum(uint8_t a, uint8_t b, uint64_t c, uint64_t d) {
  std::array<char, 2 + 8 + 8> buffer;
  folly::storeUnaligned<uint8_t>(buffer.data() + 0, a);
  folly::storeUnaligned<uint8_t>(buffer.data() + 1, b);
  folly::storeUnaligned<uint64_t>(buffer.data() + 2, c);
  folly::storeUnaligned<uint64_t>(buffer.data() + 2 + 8, d);

  uint16_t checksum = 0;
  for (std::size_t i = 0; i < buffer.size(); i += 2) {
    checksum += folly::loadUnaligned<uint16_t>(buffer.data() + i);
  }

  return checksum;
}

int main() {
  uint8_t a = 0, b = 0;
  uint64_t c = 0, d = 0;

  std::cout << checksum(a, b, c, d) << std::endl;

  return 0;
}

Compiler version: g++ (Ubuntu 11.4.0-1ubuntu1~22.04) 11.4.0
Compiler flags: g++ -std=c++17 -O2