Hudson: Is this gonna be a standup fight, sir, or another bughunt?
Gorman: All we know is that there's still no contact with the colony, and that a xenomorph may be involved.
Frost: Excuse me sir, a-a what?
Gorman: A xenomorph.
Hicks: It's a bughunt.

-- Aliens, 1986

These subsystems need rethinking and revision and refactoring, because:

• hashes
  • the Hash PMC is too entertwined with the guts of src/hash.c which knows too much about the internals of Hash PMCs
  • it's not clear if the hash/bucket algorithm is sufficiently collision free
  • OrderedHash is a mess of semantics and implementation
  • some Parrot systems need C-like hashes while user-visible parts of Parrot need PMC-ish hashes

(Perhaps now is a good time to re-examine the thought of using an external hash library rather than re-inventing our own. --coke)

• CLI argument parsing
  • The current code is closely tied to imcc and will inhibit the eventual migration to pirc.
  • It's not possible to add new options at runtime.
  • It's not possible for subsystems to register new options.
  • Subsystems do not have access to arguments passed directly to the parrot binary.

• lvalue model (WhyDoesNQPGenerateInefficientCode)
  • PIR does not have clear and consistent assignment/binding semantics.
  • This forces nqp to be rather pessimal in the assumptions it makes about the contents of lexical variables.
  • It's also a source (actual, not potential) of confusion for HLL developers.
  • Note: Research into this problem should include a look at how other VMs (e.g. JVM, CLI, PyPy, CPython, Perl 5, MRI, etc) deal with this. PyPy may be of special interest because that project aims for a similar niche to Parrot.