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Make MemoryAssert.assertGC stricter when soft references are disallowed #1029

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Make MemoryAssert.assertGC stricter when soft references are disallowed #1029

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56 changes: 24 additions & 32 deletions src/main/java/org/jvnet/hudson/test/MemoryAssert.java
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Original file line number Diff line number Diff line change
Expand Up @@ -161,6 +161,7 @@ public static void assertGC(WeakReference<?> reference) {

/**
* Forces GC by causing an OOM and then verifies the given {@link WeakReference} has been garbage collected.
* <p>Beware that failures messages can be misleading and you may need to use heap dumps to diagnose issues.
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@dwnusbaum dwnusbaum Sep 25, 2025

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Suggested change
* <p>Beware that failures messages can be misleading and you may need to use heap dumps to diagnose issues.
* <p>Beware that failure messages can be misleading, and you may need to use heap dumps to diagnose issues.

* @param reference object used to verify garbage collection.
* @param allowSoft if true, pass even if {@link SoftReference}s apparently needed to be cleared by forcing an {@link OutOfMemoryError};
* if false, fail in such a case (though the failure will be slow)
Expand Down Expand Up @@ -192,29 +193,18 @@ public static void assertGC(WeakReference<?> reference, boolean allowSoft) {
Object obj = reference.get();
if (obj != null) {
softErr = "Apparent soft references to " + obj + ": "
+ fromRoots(Set.of(obj), null, null, new Filter() {
final Field referent;

{
try {
referent = Reference.class.getDeclaredField("referent");
} catch (NoSuchFieldException x) {
throw new AssertionError(x);
}
}

@Override
public boolean accept(Object obj, Object referredFrom, Field reference) {
return !referent.equals(reference) || !(referredFrom instanceof WeakReference);
}
})
+ fromRoots(Set.of(obj), null, null, new SkipWeakReferencesFilter())
+ "; apparent weak references: "
+ fromRoots(
Set.of(obj), null, null, ScannerUtils.skipObjectsFilter(Set.of(reference), true));
System.err.println(softErr);
}
}
}
if (softErr != null) {
// Sometimes soft references can be cleared prior to an OutOfMemoryError occurring.
fail(softErr);
}
objects = null;
System.gc();
Object obj = reference.get();
Expand All @@ -228,22 +218,7 @@ public boolean accept(Object obj, Object referredFrom, Field reference) {
fail(rootRefs.toString());
} else {
System.err.println("Did not find any strong references to " + obj + ", looking for soft references…");
rootRefs = fromRoots(Set.of(obj), null, null, new Filter() {
final Field referent;

{
try {
referent = Reference.class.getDeclaredField("referent");
} catch (NoSuchFieldException x) {
throw new AssertionError(x);
}
}

@Override
public boolean accept(Object obj, Object referredFrom, Field reference) {
return !referent.equals(reference) || !(referredFrom instanceof WeakReference);
}
});
rootRefs = fromRoots(Set.of(obj), null, null, new SkipWeakReferencesFilter());
if (!rootRefs.isEmpty()) {
fail(rootRefs.toString());
} else {
Expand Down Expand Up @@ -343,4 +318,21 @@ public void visitObject(ObjectMap map, Object object) {
}
}
}

private static class SkipWeakReferencesFilter implements Filter {
static final Field referent;

static {
try {
referent = Reference.class.getDeclaredField("referent");
} catch (NoSuchFieldException x) {
throw new AssertionError(x);
}
}

@Override
public boolean accept(Object obj, Object referredFrom, Field reference) {
return !referent.equals(reference) || !(referredFrom instanceof WeakReference);
}
}
}