elharo commented on issue #1997:
URL:
https://github.com/apache/maven-resolver/issues/1997#issuecomment-5064177136
The issue reported in apache/maven-resolver #1997 is not a bug. No action
should be taken to modify the code, and the issue should be closed as a false
positive.
The bug report claims that the fast-path get() operation in
ConcurrentWeakCache contains a flaw where it can return a "stale reference" if
the key is garbage collected immediately after the check. This claim is
technically incorrect and contradicts Java's memory model and garbage
collection mechanics for the following reasons:
Strong References Prevent Garbage Collection: The caller of
putIfAbsent(K key, V value) provides the key object as a method argument.
Because the calling thread holds a strong reference to key on its execution
stack, the Java Garbage Collector (GC) cannot collect the key while the method
is executing.
Safe Value Retrieval: When the fast-path executes V existing = get(key),
the method extracts and returns the value. If the value is found, existing
becomes a strong reference on the thread's stack. Once a strong reference is
established, the object is protected from garbage collection.
No "Stale" Strong References: Java does not return "stale" strong
references. If the underlying data structure uses WeakReference or
SoftReference, the act of unwrapping the reference yields either a valid,
strong reference to the object or null (if the object was already collected).
It is impossible to return a non-null reference that subsequently becomes
invalid while still in scope.
The fast-path optimization is correct by design. The issue was labeled as
part of an "LLM grabbag" (#1944), indicating it is an automated finding. It is
a hallucination of a concurrent race condition that does not exist in the JVM.
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