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[TrimmableTypeMap] Support legacy RegisterNativeMembers #11652

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[TrimmableTypeMap] Support legacy RegisterNativeMembers #11652

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6a3da6e
[Mono.Android] Support legacy RegisterNativeMembers in trimmable typemap
simonrozsival Jun 14, 2026
4e2eab2
[Mono.Android] Reuse fast path for legacy RegisterNativeMembers (trim…
simonrozsival Jun 14, 2026
6f7f6c0
[Mono.Android] Share string-based JNI native registration
simonrozsival Jun 15, 2026
c32bd77
[Mono.Android] Mark string JNI registration dynamic-code unsafe
simonrozsival Jun 15, 2026
39477d6
[Mono.Android] Fail fast when string JNI registration is disabled
simonrozsival Jun 15, 2026
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148 changes: 8 additions & 140 deletions src/Mono.Android/Android.Runtime/AndroidRuntime.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -2,13 +2,12 @@
using System.Collections.Generic;
using System.Diagnostics;
using System.Globalization;
using System.Reflection;
using System.Runtime.CompilerServices;
using System.Runtime.Versioning;
using System.Threading;
using System.Reflection;

using Java.Interop;
using Java.Interop.Tools.TypeNameMappings;
using Microsoft.Android.Runtime;
using System.Diagnostics.CodeAnalysis;

Expand Down Expand Up @@ -380,34 +379,6 @@ protected override IEnumerable<string> GetSimpleReferences (Type type)
return null;
}

delegate Delegate GetCallbackHandler ();

static MethodInfo? dynamic_callback_gen;

// See ExportAttribute.cs
[UnconditionalSuppressMessage ("Trimming", "IL2026", Justification = "Mono.Android.Export.dll is preserved when [Export] is used via [DynamicDependency].")]
[UnconditionalSuppressMessage ("Trimming", "IL2075", Justification = "Mono.Android.Export.dll is preserved when [Export] is used via [DynamicDependency].")]
static Delegate CreateDynamicCallback (MethodInfo method)
{
if (dynamic_callback_gen == null) {
var assembly = Assembly.Load ("Mono.Android.Export");
if (assembly == null)
throw new InvalidOperationException ("To use methods marked with ExportAttribute, Mono.Android.Export.dll needs to be referenced in the application");
var type = assembly.GetType ("Java.Interop.DynamicCallbackCodeGenerator");
if (type == null)
throw new InvalidOperationException ("The referenced Mono.Android.Export.dll does not match the expected version. The required type was not found.");
dynamic_callback_gen = type.GetMethod ("Create");
if (dynamic_callback_gen == null)
throw new InvalidOperationException ("The referenced Mono.Android.Export.dll does not match the expected version. The required method was not found.");
}
return (Delegate)dynamic_callback_gen.Invoke (null, new object [] { method })!;
}

// [Export] callback delegates are created dynamically via DynamicCallbackCodeGenerator and are not
// cached in static fields (unlike non-[Export] connector delegates). Without rooting them here,
// CoreCLR's GC can collect them between JNI registration and first invocation, causing a crash.
static readonly Lock prevent_delegate_gc_lock = new Lock ();
static readonly List<Delegate> prevent_delegate_gc = new List<Delegate> ();
static List<JniNativeMethodRegistration> sharedRegistrations = new List<JniNativeMethodRegistration> ();

static bool FastRegisterNativeMembers (JniType nativeClass, Type type, ReadOnlySpan<char> methods)
Expand Down Expand Up @@ -488,9 +459,6 @@ public override void RegisterNativeMembers (
string? methods) =>
RegisterNativeMembers (nativeClass, type, methods.AsSpan ());

[UnconditionalSuppressMessage ("Trimming", "IL2057", Justification = "Type.GetType() can never statically know the string value parsed from parameter 'methods'.")]
[UnconditionalSuppressMessage ("Trimming", "IL2067", Justification = "Delegate.CreateDelegate() can never statically know the string value parsed from parameter 'methods'.")]
[UnconditionalSuppressMessage ("Trimming", "IL2072", Justification = "Delegate.CreateDelegate() can never statically know the string value parsed from parameter 'methods'.")]
public override void RegisterNativeMembers (
JniType nativeClass,
[DynamicallyAccessedMembers (MethodsAndPrivateNested)] Type type,
Expand All @@ -505,121 +473,21 @@ public override void RegisterNativeMembers (
return;
}

int methodCount = CountMethods (methods);
if (methodCount < 1) {
if (jniAddNativeMethodRegistrationAttributePresent) {
if (RuntimeFeature.StringBasedJniRegistration) {
if (!NativeMethodRegistration.TryRegisterNativeMembers (nativeClass, type, methods) &&
jniAddNativeMethodRegistrationAttributePresent) {
base.RegisterNativeMembers (nativeClass, type, methods.ToString ());
}
return;
}

JniNativeMethodRegistration [] natives = new JniNativeMethodRegistration [methodCount];
int nativesIndex = 0;
MethodInfo []? typeMethods = null;

ReadOnlySpan<char> methodsSpan = methods;
bool needToRegisterNatives = false;

while (!methodsSpan.IsEmpty) {
int newLineIndex = methodsSpan.IndexOf ('\n');

ReadOnlySpan<char> methodLine = methodsSpan.Slice (0, newLineIndex != -1 ? newLineIndex : methodsSpan.Length);
if (!methodLine.IsEmpty) {
SplitMethodLine (methodLine,
out ReadOnlySpan<char> name,
out ReadOnlySpan<char> signature,
out ReadOnlySpan<char> callbackString,
out ReadOnlySpan<char> callbackDeclaringTypeString);

Delegate? callback = null;
if (callbackString.SequenceEqual ("__export__")) {
var mname = name.Slice (2);
MethodInfo? minfo = null;
typeMethods ??= type.GetMethods (BindingFlags.Public | BindingFlags.NonPublic | BindingFlags.Instance | BindingFlags.Static);
foreach (var mi in typeMethods)
if (mname.SequenceEqual (mi.Name) && signature.SequenceEqual (JavaNativeTypeManager.GetJniSignature (mi))) {
minfo = mi;
break;
}

if (minfo == null)
throw new InvalidOperationException (FormattableString.Invariant ($"Specified managed method '{mname.ToString ()}' was not found. Signature: {signature.ToString ()}"));
callback = CreateDynamicCallback (minfo);
lock (prevent_delegate_gc_lock) {
prevent_delegate_gc.Add (callback);
}
needToRegisterNatives = true;
} else {
Type callbackDeclaringType = type;
if (!callbackDeclaringTypeString.IsEmpty) {
callbackDeclaringType = Type.GetType (callbackDeclaringTypeString.ToString (), throwOnError: true)!;
}
while (callbackDeclaringType.ContainsGenericParameters) {
callbackDeclaringType = callbackDeclaringType.BaseType!;
}

GetCallbackHandler connector = (GetCallbackHandler) Delegate.CreateDelegate (typeof (GetCallbackHandler),
callbackDeclaringType, callbackString.ToString ());
callback = connector ();
}

if (callback != null) {
needToRegisterNatives = true;
natives [nativesIndex++] = new JniNativeMethodRegistration (name.ToString (), signature.ToString (), callback);
}
}

methodsSpan = newLineIndex != -1 ? methodsSpan.Slice (newLineIndex + 1) : default;
}

if (needToRegisterNatives) {
JniEnvironment.Types.RegisterNatives (nativeClass.PeerReference, natives, nativesIndex);
}
throw new NotSupportedException (
$"Unable to register native methods for '{type.FullName}': string-based JNI registration is disabled " +
$"and no fast native registration entry was found. Re-enable it by setting " +
$"_AndroidEnableStringBasedJniRegistration=true.");
} catch (Exception e) {
JniEnvironment.Runtime.RaisePendingException (e);
}

bool ShouldRegisterDynamically (string callbackTypeName, string callbackString, string typeName, string callbackName)
{
if (String.Compare (typeName, callbackTypeName, StringComparison.Ordinal) != 0) {
return false;
}

return String.Compare (callbackName, callbackString, StringComparison.Ordinal) == 0;
}
}

static int CountMethods (ReadOnlySpan<char> methodsSpan)
{
int count = 0;
while (!methodsSpan.IsEmpty) {
count++;

int newLineIndex = methodsSpan.IndexOf ('\n');
methodsSpan = newLineIndex != -1 ? methodsSpan.Slice (newLineIndex + 1) : default;
}
return count;
}

static void SplitMethodLine (
ReadOnlySpan<char> methodLine,
out ReadOnlySpan<char> name,
out ReadOnlySpan<char> signature,
out ReadOnlySpan<char> callback,
out ReadOnlySpan<char> callbackDeclaringType)
{
int colonIndex = methodLine.IndexOf (':');
name = methodLine.Slice (0, colonIndex);
methodLine = methodLine.Slice (colonIndex + 1);

colonIndex = methodLine.IndexOf (':');
signature = methodLine.Slice (0, colonIndex);
methodLine = methodLine.Slice (colonIndex + 1);

colonIndex = methodLine.IndexOf (':');
callback = methodLine.Slice (0, colonIndex != -1 ? colonIndex : methodLine.Length);

callbackDeclaringType = colonIndex != -1 ? methodLine.Slice (colonIndex + 1) : default;
}
}

Expand Down
30 changes: 25 additions & 5 deletions src/Mono.Android/Android.Runtime/JNIEnvInit.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -88,6 +88,18 @@ static Type TypeGetType (string typeName) =>
androidRuntime.TypeManager.RegisterNativeMembers (jniType, type, methods);
}

[UnmanagedCallersOnly]
static void RegisterNativesViaTrimmableTypeMap (IntPtr env, IntPtr klass, IntPtr nativeClassHandle)
{
try {
TrimmableTypeMap.Instance.RegisterNatives (nativeClassHandle);
} catch (Exception ex) {
var classRef = new JniObjectReference (nativeClassHandle);
var className = JniEnvironment.Types.GetJniTypeNameFromClass (classRef);
Environment.FailFast ($"TrimmableTypeMap: Failed to register natives for class '{className}'.", ex);
}
}

// This must be called by NativeAOT before InitializeJniRuntime, as early as possible
internal static void NativeAotInitializeMaxGrefGet ()
{
Expand Down Expand Up @@ -157,9 +169,10 @@ internal static unsafe void Initialize (JnienvInitializeArgs* args)

args->propagateUncaughtExceptionFn = (IntPtr)(delegate* unmanaged<IntPtr, IntPtr, IntPtr, void>)&PropagateUncaughtException;

if (!RuntimeFeature.TrimmableTypeMap) {
if (RuntimeFeature.StringBasedJniRegistration) {
args->registerJniNativesFn = (IntPtr)(delegate* unmanaged<IntPtr, int, IntPtr, IntPtr, int, void>)&RegisterJniNatives;
}

RunStartupHooksIfNeeded ();
SetSynchronizationContext ();
}
Expand Down Expand Up @@ -224,10 +237,17 @@ static void InitializeTrimmableTypeMapDataIfNeeded ()

static void RegisterTrimmableTypeMapNativeMethodsIfNeeded ()
{
if (RuntimeFeature.TrimmableTypeMap) {
// TypeMapLoader.Initialize() only loads managed typemap data. Registering
// mono.android.Runtime natives requires JniRuntime.Current and its ClassLoader.
TrimmableTypeMap.RegisterNativeMethods ();
if (!RuntimeFeature.TrimmableTypeMap) {
return;
}

using var runtimeClass = new JniType ("mono/android/Runtime"u8);
unsafe {
fixed (byte* name = "registerNatives"u8, sig = "(Ljava/lang/Class;)V"u8) {
var onRegisterNatives = (IntPtr)(delegate* unmanaged<IntPtr, IntPtr, IntPtr, void>)&RegisterNativesViaTrimmableTypeMap;
var method = new JniNativeMethod (name, sig, onRegisterNatives);
JniEnvironment.Types.RegisterNatives (runtimeClass.PeerReference, [method]);
}
}
}

Expand Down
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