java-topology/defects/elixir/patch/CLEAN.md

Elixir — CWE-407 Diamond Recursion Scan: CLEAN

Scan Date

2026-03-29

Targets Checked

1. Behaviour/callback verification (Module.Behaviour)

• File: lib/elixir/lib/module/behaviour.ex, check_behaviours_and_impls
• Mechanism: Calls behaviour.behaviour_info(:callbacks) — returns a precomputed list from the compiled BEAM module. No recursive traversal of the behaviour graph.
• Result: CLEAN.

2. Protocol consolidation (lib/elixir/lib/protocol.ex)

• Mechanism: Protocol dispatch uses __impl__/1 which is compiled into the protocol module as a direct function call — O(1) dispatch.
• Protocol.consolidate/2 iterates impls list linearly — no recursive traversal.
• Result: CLEAN.

3. Import deduplication (Erlang layer, elixir_import.erl)

• File: lib/elixir/src/elixir_import.erl, ensure_no_duplicates (line 225)
• lists:member({Name, Arity}, Acc) in a fold — O(N²) over import list.
• N is bounded: import lists are typically ≤100 entries per module, no diamond graph structure. This is a minor quadratic scan, not an exponential diamond defect.
• Result: Not CWE-407 (bounded, not graph-recursive).

4. Macro expansion / @impl checking

• File: lib/elixir/lib/module/parallel_checker.ex
• defining?/2 uses Enum.any? over a waiting list — bounded by concurrent module compilation queue, not a type hierarchy depth.
• Result: CLEAN for diamond recursion.

5. Erlang runtime module loading

• Elixir relies on Erlang/OTP module loading which tracks loaded modules in a global code_server ETS table — O(1) lookup.
• Result: CLEAN.

Conclusion

No CWE-407 diamond recursion defects found in Elixir. Behaviour callbacks use precomputed BEAM metadata; protocol dispatch is compiled to direct calls; module loading uses ETS-backed sets.