russell@unturf.com
1dee074618
findAndVerifyWindowGrace() recurses over parent GraphNodes without a visited accumulator. Kafka Streams GraphNode is a genuine DAG (addChild wires parent→child with multiple parents allowed), so a diamond topology causes 2^D recursive calls. Fix: thread an IdentityHashMap<GraphNode,Long> memo through recursion; memoize on first visit, return cached result on revisit. 8/8 unit tests PASS; D=10 defect count=3071 vs patched O(N). Diamond-recursion CLEAN markers added for: flink, neo4j, janusgraph, tinkerpop, dgraph, zookeeper, storm, ant, gradle, graal, eclipse-jdt, exposed, intellij, kotlin, scala3, hibernate-0007 (prior session work now committed).
47 lines
2.2 KiB
Markdown
47 lines
2.2 KiB
Markdown
# Eclipse JDT — Diamond Recursion CWE-407 Scan: CLEAN
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**Pattern:** Recursive cycle/reachability without visited set (O(2^D) on diamond DAGs)
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**Scan date:** 2026-03-29
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**Scope:** `org.eclipse.jdt.core/`, `org.eclipse.jdt.core.compiler.batch/`
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## Method
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Searched for `hasCycle`, `isCyclic`, `isReachable`, `canReach`, `hasPath`,
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`detectCycle` across all Java sources. Examined each recursive function for
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a missing visited-accumulator parameter.
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## Key candidates reviewed
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### `ClassScope.detectHierarchyCycle()`
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`org.eclipse.jdt.core.compiler.batch/.../lookup/ClassScope.java` line 1474.
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Recursive — calls itself at lines 1517 and 1535. However, it avoids diamond
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blowup via per-node memoization embedded in `TagBits`:
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- Sets `TagBits.BeginHierarchyCheck` on each node before descending
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- Checks `isHierarchyBeingActivelyConnected()` (an IN_PROGRESS flag) before recursing
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- Checks `(superType.tagBits & TagBits.BeginHierarchyCheck) == 0` to skip already-visited nodes
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- For binary supertypes, propagates `TagBits.HierarchyHasProblems` upward to avoid re-expansion
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This is a "colored node" visited-set pattern where the visited state lives on the
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node object itself rather than in an external set. Equivalent complexity to DFS
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with a visited set — O(V+E). Not the diamond recursion anti-pattern.
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### `InferenceContext18.isReachable()`
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`org.eclipse.jdt.core.compiler.batch/.../lookup/InferenceContext18.java` line 1688.
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Signature: `private boolean isReachable(Map<ConstraintFormula,Set<ConstraintFormula>> deps, ConstraintFormula from, ConstraintFormula to, Set<ConstraintFormula> nodesVisited, Set<ConstraintFormula> nodesInCycle)`
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Explicitly takes a `nodesVisited` set parameter — `nodesVisited.add(from)` at line 1695
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is the visited guard. CLEAN.
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### `ModuleBinding.collectAllDependencies()` / `collectTransitiveDependencies()`
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`org.eclipse.jdt.core.compiler.batch/.../lookup/ModuleBinding.java` lines 419, 426.
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Uses `deps.add(m)` — the Set parameter itself is the visited accumulator. If `add()`
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returns false (already present), the recursive call is skipped. CLEAN.
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## Verdict
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CLEAN for diamond recursion pattern. Eclipse JDT uses either per-node TagBits
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memoization or explicit Set parameters to prevent diamond blowup. No unprotected
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recursive DAG traversal found.
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