Implement StableObjPtr for Kotlin N

Interop/Runtime/src/native/kotlin/kotlinx/cinterop/NativeCallbacks.kt

@@ -1,5 +1,51 @@
 package kotlinx.cinterop
 
+/**
+ * This class provides a way to create a stable handle to any Kotlin object.
+ * Its [value] can be safely passed to native code e.g. to be received in a Kotlin callback.
+ *
+ * Any [StableObjPtr] should be manually [disposed][dispose]
+ */
+data class StableObjPtr private constructor(val value: COpaquePointer) {
+
+    companion object {
+
+        /**
+         * Creates a handle for given object.
+         */
+        fun create(any: Any) = fromValue(createStablePointer(any))
+
+        /**
+         * Creates [StableObjPtr] from given raw value.
+         *
+         * @param value must be a [value] of some [StableObjPtr]
+         */
+        fun fromValue(value: COpaquePointer) = StableObjPtr(value)
+    }
+
+    /**
+     * Disposes the handle. It must not be [used][get] after that.
+     */
+    fun dispose() {
+        disposeStablePointer(value)
+    }
+
+    /**
+     * Returns the object this handle was [created][create] for.
+     */
+    fun get(): Any = derefStablePointer(value)
+
+}
+
+@SymbolName("Kotlin_Interop_createStablePointer")
+private external fun createStablePointer(any: Any): COpaquePointer
+
+@SymbolName("Kotlin_Interop_disposeStablePointer")
+private external fun disposeStablePointer(pointer: COpaquePointer)
+
+@SymbolName("Kotlin_Interop_derefStablePointer")
+private external fun derefStablePointer(pointer: COpaquePointer): Any
+
 /**
  * The type of C function which can be constructed from the appropriate Kotlin function without using any adapter.
  */

Interop/Runtime/src/native/kotlin/kotlinx/cinterop/Varargs.kt

@@ -107,7 +107,7 @@ fun callWithVarargs(codePtr: NativePtr, returnValuePtr: NativePtr, returnTypeKin
             fixedArguments.size, totalArgumentsNumber)
 }
 
-@SymbolName("callWithVarargs")
+@SymbolName("Kotlin_Interop_callWithVarargs")
 private external fun callWithVarargs(codePtr: NativePtr, returnValuePtr: NativePtr, returnTypeKind: FfiTypeKind,
                                      arguments: NativePtr, argumentTypeKinds: NativePtr,
                                      fixedArgumentsNumber: Int, totalArgumentsNumber: Int)