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[TrimmableTypeMap] Add exception handling to UCO constructor callbacks (nctor_*_uco) #11178

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Merged
jonathanpeppers merged 3 commits into from
Apr 22, 2026
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[TrimmableTypeMap] Add exception handling to UCO constructor callbacks (nctor_*_uco) #11178

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0247227
Initial plan
Copilot Apr 22, 2026
ecf14a0
Add exception handling to UCO constructor callbacks (nctor_*_uco)
Copilot Apr 22, 2026
96c74f2
Address review comments: extract helper, add IL call assertions, add …
simonrozsival Apr 22, 2026
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45 changes: 45 additions & 0 deletions src/Microsoft.Android.Sdk.TrimmableTypeMap/Generator/PEAssemblyBuilder.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -316,6 +316,51 @@ public MethodDefinitionHandle EmitBody (string name, MethodAttributes attrs,
bodyOffset, default);
}

/// <summary>
/// Emits a method body with full support for exception regions (try/catch/finally).
/// The callback receives both the <see cref="InstructionEncoder"/> and the
/// <see cref="ControlFlowBuilder"/> so it can emit IL and register exception regions
/// (e.g. via <c>cfb.AddCatchRegion</c> / <c>cfb.AddFinallyRegion</c>) in one pass.
/// A <see cref="ControlFlowBuilder"/> is always created for this overload.
/// </summary>
public MethodDefinitionHandle EmitBody (string name, MethodAttributes attrs,
Action<BlobEncoder> encodeSig,
Action<InstructionEncoder, ControlFlowBuilder> emitIL,
Action<BlobBuilder>? encodeLocals)
{
_sigBlob.Clear ();
encodeSig (new BlobEncoder (_sigBlob));
// Capture the sig blob handle before emitIL, because emitIL callbacks
// may call AddMemberRef which clears and repopulates _sigBlob.
var sigBlobHandle = Metadata.GetOrAddBlob (_sigBlob);
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StandaloneSignatureHandle localSigHandle = default;
if (encodeLocals != null) {
var localSigBlob = new BlobBuilder (32);
encodeLocals (localSigBlob);
localSigHandle = Metadata.AddStandaloneSignature (Metadata.GetOrAddBlob (localSigBlob));
}

_codeBlob.Clear ();
var cfb = new ControlFlowBuilder ();
var encoder = new InstructionEncoder (_codeBlob, cfb);
emitIL (encoder, cfb);

while (ILBuilder.Count % 4 != 0) {
ILBuilder.WriteByte (0);
}
var bodyEncoder = new MethodBodyStreamEncoder (ILBuilder);
int bodyOffset = localSigHandle.IsNil
? bodyEncoder.AddMethodBody (encoder)
: bodyEncoder.AddMethodBody (encoder, maxStack: 8, localSigHandle, MethodBodyAttributes.InitLocals);

return Metadata.AddMethodDefinition (
attrs, MethodImplAttributes.IL,
Metadata.GetOrAddString (name),
sigBlobHandle,
bodyOffset, default);
}

/// <summary>
/// Builds a <c>TypeSpec</c> for a closed generic type with a single type argument.
/// For example, <c>MakeGenericTypeSpec(openAttrRef, javaLangObjectRef)</c> produces
Expand Down
255 changes: 198 additions & 57 deletions src/Microsoft.Android.Sdk.TrimmableTypeMap/Generator/TypeMapAssemblyEmitter.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -100,6 +100,13 @@ sealed class TypeMapAssemblyEmitter
TypeReferenceHandle _jniNativeMethodRef;
TypeReferenceHandle _jniEnvironmentRef;
TypeReferenceHandle _jniEnvironmentTypesRef;
TypeReferenceHandle _jniTransitionRef;
TypeReferenceHandle _jniRuntimeRef;
TypeReferenceHandle _exceptionRef;

MemberReferenceHandle _beginMarshalMethodRef;
MemberReferenceHandle _endMarshalMethodRef;
MemberReferenceHandle _onUserUnhandledExceptionRef;
TypeReferenceHandle _readOnlySpanOpenRef;
TypeSpecificationHandle _readOnlySpanOfJniNativeMethodSpec;
MemberReferenceHandle _jniNativeMethodCtorRef;
Expand Down Expand Up @@ -205,6 +212,12 @@ void EmitTypeReferences ()
metadata.GetOrAddString ("Java.Interop"), metadata.GetOrAddString ("JniEnvironment"));
_jniEnvironmentTypesRef = metadata.AddTypeReference (_jniEnvironmentRef,
default, metadata.GetOrAddString ("Types"));
_jniTransitionRef = metadata.AddTypeReference (_javaInteropRef,
metadata.GetOrAddString ("Java.Interop"), metadata.GetOrAddString ("JniTransition"));
_jniRuntimeRef = metadata.AddTypeReference (_javaInteropRef,
metadata.GetOrAddString ("Java.Interop"), metadata.GetOrAddString ("JniRuntime"));
_exceptionRef = metadata.AddTypeReference (_pe.SystemRuntimeRef,
metadata.GetOrAddString ("System"), metadata.GetOrAddString ("Exception"));

// ReadOnlySpan<JniNativeMethod> — TypeSpec for generic instantiation
_readOnlySpanOpenRef = metadata.AddTypeReference (_pe.SystemRuntimeRef,
Expand Down Expand Up @@ -295,6 +308,31 @@ void EmitMemberReferences ()
// Pre-compute the UCO attribute blob — it's always the same 4 bytes (prolog + no named args)
_ucoAttrBlobHandle = _pe.BuildAttributeBlob (b => { });

// JniEnvironment.BeginMarshalMethod(nint jnienv, out JniTransition, out JniRuntime?) -> bool
_beginMarshalMethodRef = _pe.AddMemberRef (_jniEnvironmentRef, "BeginMarshalMethod",
sig => sig.MethodSignature ().Parameters (3,
rt => rt.Type ().Boolean (),
p => {
p.AddParameter ().Type ().IntPtr ();
p.AddParameter ().Type (isByRef: true).Type (_jniTransitionRef, true);
p.AddParameter ().Type (isByRef: true).Type (_jniRuntimeRef, false);
}));

// JniEnvironment.EndMarshalMethod(ref JniTransition) -> void
_endMarshalMethodRef = _pe.AddMemberRef (_jniEnvironmentRef, "EndMarshalMethod",
sig => sig.MethodSignature ().Parameters (1,
rt => rt.Void (),
p => p.AddParameter ().Type (isByRef: true).Type (_jniTransitionRef, true)));

// JniRuntime.OnUserUnhandledException(ref JniTransition, Exception) -> void
_onUserUnhandledExceptionRef = _pe.AddMemberRef (_jniRuntimeRef, "OnUserUnhandledException",
sig => sig.MethodSignature (isInstanceMethod: true).Parameters (2,
rt => rt.Void (),
p => {
p.AddParameter ().Type (isByRef: true).Type (_jniTransitionRef, true);
p.AddParameter ().Type ().Type (_exceptionRef, false);
}));

EmitTypeMapAttributeCtorRef ();
EmitTypeMapAssociationAttributeCtorRef ();
EmitJavaPeerAliasesAttributeCtorRef ();
Expand Down Expand Up @@ -841,88 +879,191 @@ MethodDefinitionHandle EmitUcoConstructor (UcoConstructorData uco, JavaPeerProxy
var ctorRef = AddJavaInteropActivationCtorRef (
activationCtor.IsOnLeafType ? targetTypeRef : _pe.ResolveTypeRef (activationCtor.DeclaringType));

// Locals:
// 0: JniTransition (envp) — out-parameter for BeginMarshalMethod
// 1: JniRuntime? (runtime) — out-parameter for BeginMarshalMethod
// 2: Exception (e) — catch variable
// 3: JniObjectReference (jniRef) — needed for JavaInterop-style activation
handle = _pe.EmitBody (uco.WrapperName,
MethodAttributes.Public | MethodAttributes.Static | MethodAttributes.HideBySig,
encodeSig,
encoder => {
// Skip activation if the object is being created from managed code
// (e.g., JNIEnv.StartCreateInstance / JNIEnv.NewObject).
var skipLabel = encoder.DefineLabel ();
encoder.Call (_withinNewObjectScopeRef);
encoder.Branch (ILOpCode.Brtrue, skipLabel);

(encoder, cfb) => EmitUcoConstructorBodyWithMarshal (encoder, cfb, enc => {
if (!activationCtor.IsOnLeafType) {
encoder.OpCode (ILOpCode.Ldtoken);
encoder.Token (targetTypeRef);
encoder.Call (_getTypeFromHandleRef);
encoder.Call (_getUninitializedObjectRef);
encoder.OpCode (ILOpCode.Castclass);
encoder.Token (targetTypeRef);
enc.OpCode (ILOpCode.Ldtoken);
enc.Token (targetTypeRef);
enc.Call (_getTypeFromHandleRef);
enc.Call (_getUninitializedObjectRef);
enc.OpCode (ILOpCode.Castclass);
enc.Token (targetTypeRef);
}

encoder.LoadLocalAddress (0);
encoder.LoadArgument (1); // self
encoder.Call (_jniObjectReferenceCtorRef);
enc.LoadLocalAddress (3); // jniRef
enc.LoadArgument (1); // self
enc.Call (_jniObjectReferenceCtorRef);

if (activationCtor.IsOnLeafType) {
encoder.LoadLocalAddress (0);
encoder.LoadConstantI4 (1); // JniObjectReferenceOptions.Copy
encoder.OpCode (ILOpCode.Newobj);
encoder.Token (ctorRef);
encoder.OpCode (ILOpCode.Pop);
enc.LoadLocalAddress (3); // ref jniRef
enc.LoadConstantI4 (1); // JniObjectReferenceOptions.Copy
enc.OpCode (ILOpCode.Newobj);
enc.Token (ctorRef);
enc.OpCode (ILOpCode.Pop);
} else {
encoder.LoadLocalAddress (0);
encoder.LoadConstantI4 (1); // JniObjectReferenceOptions.Copy
encoder.Call (ctorRef);
enc.LoadLocalAddress (3); // ref jniRef
enc.LoadConstantI4 (1); // JniObjectReferenceOptions.Copy
enc.Call (ctorRef);
}

encoder.MarkLabel (skipLabel);
encoder.OpCode (ILOpCode.Ret);
},
EncodeJniObjectReferenceLocal,
useBranches: true);
}),
EncodeUcoConstructorLocals_JavaInterop);
} else {
var ctorRef = AddActivationCtorRef (
activationCtor.IsOnLeafType ? targetTypeRef : _pe.ResolveTypeRef (activationCtor.DeclaringType));

// Locals:
// 0: JniTransition (envp) — out-parameter for BeginMarshalMethod
// 1: JniRuntime? (runtime) — out-parameter for BeginMarshalMethod
// 2: Exception (e) — catch variable
handle = _pe.EmitBody (uco.WrapperName,
MethodAttributes.Public | MethodAttributes.Static | MethodAttributes.HideBySig,
encodeSig,
encoder => {
// Skip activation if the object is being created from managed code
var skipLabel = encoder.DefineLabel ();
encoder.Call (_withinNewObjectScopeRef);
encoder.Branch (ILOpCode.Brtrue, skipLabel);

(encoder, cfb) => EmitUcoConstructorBodyWithMarshal (encoder, cfb, enc => {
if (activationCtor.IsOnLeafType) {
encoder.LoadArgument (1); // self
encoder.LoadConstantI4 (0); // JniHandleOwnership.DoNotTransfer
encoder.OpCode (ILOpCode.Newobj);
encoder.Token (ctorRef);
encoder.OpCode (ILOpCode.Pop);
enc.LoadArgument (1); // self
enc.LoadConstantI4 (0); // JniHandleOwnership.DoNotTransfer
enc.OpCode (ILOpCode.Newobj);
enc.Token (ctorRef);
enc.OpCode (ILOpCode.Pop);
} else {
encoder.OpCode (ILOpCode.Ldtoken);
encoder.Token (targetTypeRef);
encoder.Call (_getTypeFromHandleRef);
encoder.Call (_getUninitializedObjectRef);
encoder.OpCode (ILOpCode.Castclass);
encoder.Token (targetTypeRef);

encoder.LoadArgument (1); // self
encoder.LoadConstantI4 (0); // JniHandleOwnership.DoNotTransfer
encoder.Call (ctorRef);
enc.OpCode (ILOpCode.Ldtoken);
enc.Token (targetTypeRef);
enc.Call (_getTypeFromHandleRef);
enc.Call (_getUninitializedObjectRef);
enc.OpCode (ILOpCode.Castclass);
enc.Token (targetTypeRef);

enc.LoadArgument (1); // self
enc.LoadConstantI4 (0); // JniHandleOwnership.DoNotTransfer
enc.Call (ctorRef);
}

encoder.MarkLabel (skipLabel);
encoder.OpCode (ILOpCode.Ret);
},
encodeLocals: null,
useBranches: true);
}),
EncodeUcoConstructorLocals_Standard);
}
AddUnmanagedCallersOnlyAttribute (handle);
return handle;
}

/// <summary>
/// Emits the common try/catch/finally marshal-method wrapper pattern used by all
/// non-generic UCO constructor bodies:
/// <code>
/// if (!JniEnvironment.BeginMarshalMethod(jnienv, out envp, out runtime)) return;
/// try {
/// if (!JniEnvironment.WithinNewObjectScope) { [emitActivation] }
/// } catch (Exception e) {
/// runtime?.OnUserUnhandledException(ref envp, e);
/// } finally {
/// JniEnvironment.EndMarshalMethod(ref envp);
/// }
/// </code>
/// Locals 0 (JniTransition envp) and 1 (JniRuntime? runtime) must be declared by the caller.
/// Local 2 (Exception e) must also be declared. Any activation-specific locals start at index 3.
/// </summary>
void EmitUcoConstructorBodyWithMarshal (InstructionEncoder encoder, ControlFlowBuilder cfb, Action<InstructionEncoder> emitActivation)
{
var skipLabel = encoder.DefineLabel ();
var tryStart = encoder.DefineLabel ();
var catchStart = encoder.DefineLabel ();
var finallyStart = encoder.DefineLabel ();
var afterAll = encoder.DefineLabel ();
var endCatch = encoder.DefineLabel ();

// Preamble: call BeginMarshalMethod; skip everything if it returns false.
encoder.LoadArgument (0); // jnienv
encoder.LoadLocalAddress (0); // out JniTransition (local 0)
encoder.LoadLocalAddress (1); // out JniRuntime? (local 1)
encoder.Call (_beginMarshalMethodRef);
encoder.Branch (ILOpCode.Brfalse, afterAll);

// TRY — check WithinNewObjectScope, then run activation code.
encoder.MarkLabel (tryStart);
encoder.Call (_withinNewObjectScopeRef);
encoder.Branch (ILOpCode.Brtrue, skipLabel);

emitActivation (encoder);

encoder.MarkLabel (skipLabel);
encoder.Branch (ILOpCode.Leave, afterAll);

// CATCH (System.Exception e)
encoder.MarkLabel (catchStart);
encoder.StoreLocal (2); // e = exception (local 2)
encoder.LoadLocal (1); // load runtime (__r)
encoder.Branch (ILOpCode.Brfalse, endCatch);
encoder.LoadLocal (1); // __r for callvirt
encoder.LoadLocalAddress (0); // ref envp
encoder.LoadLocal (2); // e
encoder.OpCode (ILOpCode.Callvirt);
encoder.Token (_onUserUnhandledExceptionRef);
encoder.MarkLabel (endCatch);
encoder.Branch (ILOpCode.Leave, afterAll);

// FINALLY
encoder.MarkLabel (finallyStart);
encoder.LoadLocalAddress (0); // ref envp
encoder.Call (_endMarshalMethodRef);
encoder.OpCode (ILOpCode.Endfinally);

// AFTER (both finallyEnd and the early-return target)
encoder.MarkLabel (afterAll);
encoder.OpCode (ILOpCode.Ret);

// Register exception regions:
// Catch region: try [tryStart, catchStart), handler [catchStart, finallyStart)
// Finally region: try [tryStart, finallyStart), handler [finallyStart, afterAll)
cfb.AddCatchRegion (tryStart, catchStart, catchStart, finallyStart, _exceptionRef);
cfb.AddFinallyRegion (tryStart, finallyStart, finallyStart, afterAll);
}

/// <summary>
/// LOCAL_SIG for UCO constructors without JavaInterop-style activation.
/// Locals: 0=JniTransition, 1=JniRuntime, 2=Exception.
/// </summary>
void EncodeUcoConstructorLocals_Standard (BlobBuilder blob)
{
blob.WriteByte (0x07); // LOCAL_SIG
blob.WriteCompressedInteger (3);
// local 0: JniTransition (valuetype)
blob.WriteByte (0x11); // ELEMENT_TYPE_VALUETYPE
blob.WriteCompressedInteger (CodedIndex.TypeDefOrRefOrSpec (_jniTransitionRef));
// local 1: JniRuntime (class)
blob.WriteByte (0x12); // ELEMENT_TYPE_CLASS
blob.WriteCompressedInteger (CodedIndex.TypeDefOrRefOrSpec (_jniRuntimeRef));
// local 2: Exception (class)
blob.WriteByte (0x12); // ELEMENT_TYPE_CLASS
blob.WriteCompressedInteger (CodedIndex.TypeDefOrRefOrSpec (_exceptionRef));
}

/// <summary>
/// LOCAL_SIG for UCO constructors with JavaInterop-style activation.
/// Locals: 0=JniTransition, 1=JniRuntime, 2=Exception, 3=JniObjectReference.
/// </summary>
void EncodeUcoConstructorLocals_JavaInterop (BlobBuilder blob)
{
blob.WriteByte (0x07); // LOCAL_SIG
blob.WriteCompressedInteger (4);
// local 0: JniTransition (valuetype)
blob.WriteByte (0x11); // ELEMENT_TYPE_VALUETYPE
blob.WriteCompressedInteger (CodedIndex.TypeDefOrRefOrSpec (_jniTransitionRef));
// local 1: JniRuntime (class)
blob.WriteByte (0x12); // ELEMENT_TYPE_CLASS
blob.WriteCompressedInteger (CodedIndex.TypeDefOrRefOrSpec (_jniRuntimeRef));
// local 2: Exception (class)
blob.WriteByte (0x12); // ELEMENT_TYPE_CLASS
blob.WriteCompressedInteger (CodedIndex.TypeDefOrRefOrSpec (_exceptionRef));
// local 3: JniObjectReference (valuetype)
blob.WriteByte (0x11); // ELEMENT_TYPE_VALUETYPE
blob.WriteCompressedInteger (CodedIndex.TypeDefOrRefOrSpec (_jniObjectReferenceRef));
}

void EmitRegisterNatives (List<NativeRegistrationData> registrations,
Dictionary<string, MethodDefinitionHandle> wrapperHandles)
{
Expand Down
26 changes: 26 additions & 0 deletions tests/Microsoft.Android.Sdk.TrimmableTypeMap.Tests/Generator/FixtureTestBase.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -124,6 +124,13 @@ private protected static JavaPeerInfo MakeInterfacePeer (
};
}

private protected static MethodDefinitionHandle FindNctorUcoMethod (MetadataReader reader) =>
reader.MethodDefinitions.FirstOrDefault (h => {
var name = reader.GetString (reader.GetMethodDefinition (h).Name);
return name.StartsWith ("nctor_", StringComparison.Ordinal) &&
name.EndsWith ("_uco", StringComparison.Ordinal);
});

private protected static List<string> GetTypeRefNames (MetadataReader reader) =>
reader.TypeReferences
.Select (h => reader.GetTypeReference (h))
Expand All @@ -135,4 +142,23 @@ private protected static List<string> GetMemberRefNames (MetadataReader reader)
.Select (i => reader.GetMemberReference (MetadataTokens.MemberReferenceHandle (i)))
.Select (m => reader.GetString (m.Name))
.ToList ();

/// <summary>
/// Returns true if the IL byte stream contains a Call (0x28) or Callvirt (0x6F) instruction
/// whose metadata token matches <paramref name="token"/>.
/// </summary>
private protected static bool ILContainsCallToken (byte[] ilBytes, int token)
{
byte t0 = (byte)(token & 0xFF);
byte t1 = (byte)((token >> 8) & 0xFF);
byte t2 = (byte)((token >> 16) & 0xFF);
byte t3 = (byte)((token >> 24) & 0xFF);
for (int i = 0; i < ilBytes.Length - 4; i++) {
if ((ilBytes[i] == 0x28 || ilBytes[i] == 0x6F) &&
ilBytes[i + 1] == t0 && ilBytes[i + 2] == t1 &&
ilBytes[i + 3] == t2 && ilBytes[i + 4] == t3)
return true;
}
return false;
}
}
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