java-topology/defects/ninja/patch/ninja-diamond-recursion-CLEAN.md
russell@unturf.com 3986d8dc50 diamond hunt: godot-0009/0010 + meson-0002 + typeorm-0004/0005 + ts-0003; count 629→635
New diamond recursion defects (O(2^D) → O(N)):
- godot-0009: Font::_is_cyclic no visited set — CJK fallback diamond, 2648x at F=4,D=8
- godot-0010: Font::_update_rids_fb no visited set — duplicate RIDs + O(N^2) hot path
- meson-0002: get_internal_static_libraries_recurse link_whole guard missing — 132x at D=10
- typescript-0003: hasBaseType inner check() no visited set — 1024x at D=10; hot on instanceof

New O(N²) defects:
- typeorm-0004: SubjectTopologicalSorter Array.indexOf dedup — 200x at N=400
- typeorm-0005: DepGraph.createDFS result.indexOf + addDependency edge dedup — 300x at N=600

CLEAN confirmed (diamond recursion sweep): bazel, cargo, cmake, composer, dgl, diesel,
doctrine-orm, efcore, helm, mybatis, networkx-deeper, ninja, npm-arborist, peewee, pip,
rubygems, seaorm, sqlalchemy, swift

UNDF: 571→578 assigned; MOAD count: 629→635
2026-03-29 16:52:04 -04:00

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Markdown

## Diamond Recursion Scan — CLEAN
**Scan date:** 2026-03-29
**Pattern:** Recursive cycle/dependency check without visited set (CWE-407 diamond recursion, O(2^D))
### Files examined
- `src/graph.cc``RecomputeDirty`, `RecomputeNodeDirty`, `VerifyDAG`
- `src/deps_log.cc`
### Findings
**RecomputeNodeDirty:** Uses `node->status_known()` as a per-node visited flag. Before recursing into dependencies, Ninja checks `if (node->status_known()) return true;`. This is the canonical O(N) visited-flag pattern — CLEAN.
**VerifyDAG:** Uses a DFS `stack` vector for cycle detection (ancestor set). Non-recursive for the visited case — uses an `in_edge_->mark` flag to detect already-processed edges.
### Verdict: CLEAN — no diamond recursion CWE-407 found