check_cxx_source_runs("
  int main(int, char**) {
    char buf[64] = {0};
    unsigned long *ptr = (unsigned long *)(buf + 1);
    *ptr = 0xdeadbeef;
    return (*ptr & 0xff) == 0xef ? 0 : 1;
  }"
  FOLLY_HAVE_UNALIGNED_ACCESS
)