Reorganized callbacks so that the function pointers and the containing class are all pinned, which makes them safe to store inside the DLL and reuse them on subsequent update calls.

Assets/Scripts/Uniquake.cs

@@ -11,8 +11,8 @@ public class Uniquake: MonoBehaviour
     private const int MemSize = 0x4000000;  // 64 MB of heap space
     private const int MaxArgs = 50;     // Corresponds with MAX_NUM_ARGVS in engine
 
-    private UnityCallbacks callbacks = new UnityCallbacks();
     private QuakeParms quakeParms;
+    private UnityCallbacks callbacks = new UnityCallbacks();
 
     void Start()
     {
@@ -32,7 +32,7 @@ public class Uniquake: MonoBehaviour
         
         quakeParms = new QuakeParms
         {
-            baseDir = Application.dataPath,
+            baseDir = Application.persistentDataPath,
             cacheDir = null,
             argc = arguments.Length,
             argv = argv,
@@ -40,7 +40,7 @@ public class Uniquake: MonoBehaviour
             memSize = MemSize,
         };
         
-        Uniquake_Init(callbacks, quakeParms);
+        Uniquake_Init(callbacks.CallbacksPtr, quakeParms);
     }
 
     void Update()
@@ -50,6 +50,8 @@ public class Uniquake: MonoBehaviour
 
     private void OnDestroy()
     {
+        callbacks.Destroy();
+
         if (quakeParms != null)
         {
             if (quakeParms.memBase != IntPtr.Zero)
@@ -76,7 +78,7 @@ public class Uniquake: MonoBehaviour
     private static extern void Uniquake_Echo(UnityCallbacks.DebugLogCallback logCallback, [MarshalAs(UnmanagedType.LPStr)] string message);
     
     [DllImport(DllName, CallingConvention = CallingConvention.Cdecl)]
-    private static extern void Uniquake_Init(UnityCallbacks callbacks, QuakeParms parms);
+    private static extern void Uniquake_Init(IntPtr callbacks, QuakeParms parms);
 
     [DllImport(DllName, CallingConvention = CallingConvention.Cdecl)]
     private static extern void Uniquake_Update(float deltaTime);
@@ -107,20 +109,61 @@ public class Uniquake: MonoBehaviour
         return Time.realtimeSinceStartupAsDouble;
     }
 
-    [StructLayout(LayoutKind.Sequential, Pack = 0)]
+    
     private class UnityCallbacks
     {
+        private UnityCallbacksContainer container;
+        private GCHandle containerHandle;
+
+        public UnityCallbacks()
+        {
+            container = new UnityCallbacksContainer();
+
+            CreateCallback<DebugLogCallback>(Callback_DebugLog, out DebugLogHandle, out container.DebugLogPtr);
+            CreateCallback<DebugLogErrorCallback>(Callback_DebugLogError, out DebugLogErrorHandle, out container.DebugLogErrorPtr);
+            CreateCallback<ApplicationQuitCallback>(Callback_ApplicationQuit, out ApplicationQuitHandle, out container.ApplicationQuitPtr);
+            CreateCallback<RealtimeSinceStartupCallback>(Callback_RealtimeSinceStartup, out RealtimeSinceStartupHandle, out container.RealtimeSinceStartupPtr);
+            
+            containerHandle = GCHandle.Alloc(container, GCHandleType.Pinned);
+        }
+
+        public IntPtr CallbacksPtr => containerHandle.AddrOfPinnedObject();
+
+        public void Destroy()
+        {
+            containerHandle.Free();
+            DebugLogHandle.Free();
+            DebugLogErrorHandle.Free();
+            ApplicationQuitHandle.Free();
+            RealtimeSinceStartupHandle.Free();
+        }
+
+        private static void CreateCallback<TDelegate>(TDelegate callback, out GCHandle handle, out IntPtr ptr)
+        {
+            handle = GCHandle.Alloc(callback);
+            ptr = Marshal.GetFunctionPointerForDelegate(callback);
+        }
+        
         public delegate void DebugLogCallback([MarshalAs(UnmanagedType.LPStr)] string message);
-        public DebugLogCallback DebugLog = Callback_DebugLog;
+        private GCHandle DebugLogHandle;
 
         public delegate void DebugLogErrorCallback([MarshalAs(UnmanagedType.LPStr)] string message);
-        public DebugLogErrorCallback DebugLogError = Callback_DebugLogError;
+        private GCHandle DebugLogErrorHandle;
 
         public delegate void ApplicationQuitCallback(int exitCode);
-        public ApplicationQuitCallback ApplicationQuit = Callback_ApplicationQuit;
+        private GCHandle ApplicationQuitHandle;
 
         public delegate double RealtimeSinceStartupCallback();
-        public RealtimeSinceStartupCallback RealtimeSinceStartup = Callback_RealtimeSinceStartup;
+        private GCHandle RealtimeSinceStartupHandle;
+    }
+
+    [StructLayout(LayoutKind.Sequential, Pack = 0)]
+    private class UnityCallbacksContainer
+    {
+        public IntPtr DebugLogPtr;
+        public IntPtr DebugLogErrorPtr;
+        public IntPtr ApplicationQuitPtr;
+        public IntPtr RealtimeSinceStartupPtr;
     }
 
     [StructLayout(LayoutKind.Sequential, Pack = 0)]