$ git grep -n  '<< 24' src/
src/base64.h:88:        unbase64(src[i + 0]) << 24 |
src/cares_wrap.cc:83:  return static_cast<uint32_t>(p[0] << 24U) |
src/node_sockaddr.cc:305:  uint32_t check = ptr[0] << 24 | ptr[1] << 16 | ptr[2] << 8 | ptr[3];
src/util-inl.h:51:  (((x) & 0xFF) << 24) |                                                      \
src/util-inl.h:61:  (((x) & 0x0000000000FF0000ull) << 24) |

The LHS here is usually of type unsigned char but gets promoted to int (because 24 is an int) and is then left-shifted.

If the LHS >= 128, that ends up shifting into the sign bit and that's implementation-defined behavior (i.e., bad - although it probably works okay with most compilers.)

Replace 24 with 24u and all is good. But! It's probably best to abstract it away into a helper function.

cares_wrap.cc already has one - cares_get_32bit() - that handles it correctly.