Add test to check if result of methods returning big structs is corrupted due to bad handling of sret in frida 17

test/agent/src/index.ts

@@ -82,8 +82,8 @@ Il2Cpp.perform(() => {
     });
 
     test("Il2Cpp.Image::classCount", () => {
-        assert(Il2Cpp.domain.assembly("GameAssembly").image.classes.length).is(33);
-        assert(Il2Cpp.domain.assembly("GameAssembly").image.classCount).is(33);
+        assert(Il2Cpp.domain.assembly("GameAssembly").image.classes.length).is(36);
+        assert(Il2Cpp.domain.assembly("GameAssembly").image.classCount).is(36);
     });
 
     test("Il2Cpp.Class::image", () => {
@@ -619,4 +619,35 @@ Il2Cpp.perform(() => {
             "Cannot create nullable value type out of a reference type 'System.Object'"
         );
     });
+    // --- Struct return hook tests (Interceptor.replace via .implementation) ---
+
+    test("Hooked method returning medium struct with passthrough result", () => {
+        const SRT = Il2Cpp.domain.assembly("GameAssembly").image.class("StructReturnTest");
+        const method = SRT.method<Il2Cpp.ValueType>("GetMediumResult");
+
+        method.implementation = function (...args) {
+            return method.invoke(...args);
+        };
+
+        const result = method.invoke(3, 77);
+        assert(result.field<number>("Code").value).is(3);
+        assert(result.field<number>("Value").value).is(77);
+        SRT.method("GetMediumResult").revert();
+    });
+
+    test("Hooked method returning large struct (sret) with passthrough result", () => {
+        const SRT = Il2Cpp.domain.assembly("GameAssembly").image.class("StructReturnTest");
+        const method = SRT.method<Il2Cpp.ValueType>("GetLargeResult");
+        const msg = Il2Cpp.string("passthrough");
+        const entity = Il2Cpp.corlib.class("System.Object").new();
+
+        method.implementation = function (...args) {
+            return method.invoke(...args);
+        };
+
+        const result = method.invoke(5, msg, entity);
+        assert(result.field<number>("Reason").value).is(5);
+        assert(result.field<Il2Cpp.String>("Message").value.content).is("passthrough");
+        SRT.method("GetLargeResult").revert();
+    });
 }).then(() => send({ action: "stop" }));

test/src/GameAssembly.cs

@@ -355,3 +355,35 @@ static int CoalesceInt(int? a, int? b)
         return a ?? b ?? 777;
     }
 }
+
+public struct MediumStructResult
+{
+    public int Code;
+    public int Value;
+}
+
+public struct LargeStructResult
+{
+    public int Reason;
+    public string Message;
+    public object Entity;
+}
+
+public static class StructReturnTest
+{
+    public static MediumStructResult GetMediumResult(int code, int value)
+    {
+        return new MediumStructResult { Code = code, Value = value };
+    }
+
+    public static LargeStructResult GetLargeResult(int code, string message, object entity)
+    {
+        return new LargeStructResult
+        {
+            Reason = code,
+            Message = message,
+            Entity = entity
+        };
+    }
+
+}