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[Java.Interop] Defer exception creation in TryLoadClassWithFallback to fix global ref leak #1410

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jonathanpeppers merged 2 commits into from
Apr 21, 2026
+31 −16
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[Java.Interop] Defer exception creation in TryLoadClassWithFallback to fix global ref leak #1410

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3cd61c7
[Java.Interop] Defer exception creation in TryLoadClassWithFallback t…
simonrozsival Apr 21, 2026
ebbdcee
[Java.Interop] Add tests verifying TryFindClass does not leak global …
simonrozsival Apr 21, 2026
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27 changes: 11 additions & 16 deletions src/Java.Interop/Java.Interop/JniEnvironment.Types.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -114,38 +114,33 @@ static unsafe bool TryLoadClassWithFallback (JniEnvironmentInfo info, IntPtr thr
{
result = default;

var findClassThrown = new JniObjectReference (thrown, JniObjectReferenceType.Local);
LogCreateLocalRef (findClassThrown);
Exception? pendingException = info.Runtime.GetExceptionForThrowable (ref findClassThrown, JniObjectReferenceOptions.CopyAndDispose);

if (Class_forName.IsValid) {
var __args = stackalloc JniArgumentValue [3];
__args [0] = new JniArgumentValue (classNameJavaString);
__args [1] = new JniArgumentValue (true); // initialize the class
__args [2] = new JniArgumentValue (info.Runtime.ClassLoader);

var c = RawCallStaticObjectMethodA (info.EnvironmentPointer, out thrown, Class_reference.Handle, Class_forName.ID, (IntPtr) __args);
if (thrown == IntPtr.Zero) {
(pendingException as IJavaPeerable)?.Dispose ();
var c = RawCallStaticObjectMethodA (info.EnvironmentPointer, out var forNameThrown, Class_reference.Handle, Class_forName.ID, (IntPtr) __args);
if (forNameThrown == IntPtr.Zero) {
// Class.forName() succeeded; discard the FindClass throwable.
JniEnvironment.References.RawDeleteLocalRef (info.EnvironmentPointer, thrown);
result = new JniObjectReference (c, JniObjectReferenceType.Local);
JniEnvironment.LogCreateLocalRef (result);
return true;
}
RawExceptionClear (info.EnvironmentPointer);

if (pendingException != null) {
JniEnvironment.References.RawDeleteLocalRef (info.EnvironmentPointer, thrown);
} else {
var loadClassThrown = new JniObjectReference (thrown, JniObjectReferenceType.Local);
LogCreateLocalRef (loadClassThrown);
pendingException = info.Runtime.GetExceptionForThrowable (ref loadClassThrown, JniObjectReferenceOptions.CopyAndDispose);
}
JniEnvironment.References.RawDeleteLocalRef (info.EnvironmentPointer, forNameThrown);
}

if (!throwOnError) {
(pendingException as IJavaPeerable)?.Dispose ();
JniEnvironment.References.RawDeleteLocalRef (info.EnvironmentPointer, thrown);
return false;
}

// Both FindClass and Class.forName() failed; materialize a managed exception to throw.
var findClassThrown = new JniObjectReference (thrown, JniObjectReferenceType.Local);
LogCreateLocalRef (findClassThrown);
Exception? pendingException = info.Runtime.GetExceptionForThrowable (ref findClassThrown, JniObjectReferenceOptions.CopyAndDispose);
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if (pendingException != null)
throw pendingException;

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20 changes: 20 additions & 0 deletions tests/Java.Interop-Tests/Java.Interop/JniTypeUtf8Test.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -90,6 +90,26 @@ public void TryFindClass_Utf8 ()
Assert.IsFalse (notFound.IsValid);
}

[Test]
public void TryFindClass_Utf8_DoesNotLeakGlobalRefs ()
{
int grefsBefore = JniEnvironment.Runtime.GlobalReferenceCount;
JniEnvironment.Types.TryFindClass ("does/not/Exist"u8, out _);
int grefsAfter = JniEnvironment.Runtime.GlobalReferenceCount;
Assert.AreEqual (grefsBefore, grefsAfter,
"TryFindClass for non-existent classes should not leak global references");
}

[Test]
public void TryFindClass_String_DoesNotLeakGlobalRefs ()
{
int grefsBefore = JniEnvironment.Runtime.GlobalReferenceCount;
JniEnvironment.Types.TryFindClass ("does/not/Exist", out _);
int grefsAfter = JniEnvironment.Runtime.GlobalReferenceCount;
Assert.AreEqual (grefsBefore, grefsAfter,
"TryFindClass for non-existent classes should not leak global references");
}

[Test]
public void GetMethodID_Utf8_MatchesStringOverload ()
{
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