These options are only considered by the base analysis. All other analyses (especially relational) are unaffected and still assume non-top values, which defeats the point of these options.

Now thinking about these options, I'm thinking:

• exp.volatiles_are_top is for both volatile and extern (although the name doesn't say that, only the description). For clarity, it would be better to have separate options.
• If the options are going to be cleaned up, it might make sense to rename them as well, e.g. putting them under sem.*, as they define the semantics of some variables.