> Shared objects do in fact allow doing the safe subset of this, which is to load 2 versions of D that are used by packages B and C without exchanging API objec

> Shared objects do in fact allow doing the safe subset of this, which is to load 2 versions of D that are used by packages B and C without exchanging API objects. It's a fair point. But in practice this can only be done when the versions of D have different sonames - at least with the usual filesystem layout we use for dynamic linking. In that respect, Python can do it too - we just don't typically embed the major version into our Python module names, as is typical with sonames.