42 lines
1.8 KiB
Markdown
42 lines
1.8 KiB
Markdown
# Elixir — CWE-407 Diamond Recursion Scan: CLEAN
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## Scan Date
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2026-03-29
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## Targets Checked
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### 1. Behaviour/callback verification (`Module.Behaviour`)
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- **File:** `lib/elixir/lib/module/behaviour.ex`, `check_behaviours_and_impls`
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- **Mechanism:** Calls `behaviour.behaviour_info(:callbacks)` — returns a precomputed
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list from the compiled BEAM module. No recursive traversal of the behaviour graph.
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- **Result:** CLEAN.
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### 2. Protocol consolidation (`lib/elixir/lib/protocol.ex`)
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- **Mechanism:** Protocol dispatch uses `__impl__/1` which is compiled into the
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protocol module as a direct function call — O(1) dispatch.
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- `Protocol.consolidate/2` iterates `impls` list linearly — no recursive traversal.
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- **Result:** CLEAN.
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### 3. Import deduplication (Erlang layer, `elixir_import.erl`)
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- **File:** `lib/elixir/src/elixir_import.erl`, `ensure_no_duplicates` (line 225)
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- `lists:member({Name, Arity}, Acc)` in a fold — O(N²) over import list.
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- **N is bounded:** import lists are typically ≤100 entries per module, no diamond
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graph structure. This is a minor quadratic scan, not an exponential diamond defect.
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- **Result:** Not CWE-407 (bounded, not graph-recursive).
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### 4. Macro expansion / `@impl` checking
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- **File:** `lib/elixir/lib/module/parallel_checker.ex`
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- `defining?/2` uses `Enum.any?` over a waiting list — bounded by concurrent module
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compilation queue, not a type hierarchy depth.
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- **Result:** CLEAN for diamond recursion.
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### 5. Erlang runtime module loading
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- Elixir relies on Erlang/OTP module loading which tracks loaded modules in a
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global `code_server` ETS table — O(1) lookup.
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- **Result:** CLEAN.
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## Conclusion
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No CWE-407 diamond recursion defects found in Elixir. Behaviour callbacks use
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precomputed BEAM metadata; protocol dispatch is compiled to direct calls; module
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loading uses ETS-backed sets.
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