JNI: Fix native functions that take a declared QtJniTypes class

Now that QtJniTypes::Objects are no longer primitive types that are the
same as a jobject, using those types in registered native functions
breaks. JNI will call those function with a jobject on the function
pointer, and lacking any type safety, the call to the registered
function will proceed with a wrong type of object on the stack.

To fix that, register the native function via a proxy that is a variadic
argument function, and unpack the variadic arguments into a list of
typed arguments, using the types we know the user-code function wants.
Then call the function with a tuple of those types using std::apply,
which gives us type safety and implicit conversion for free.

Add a test that exercises this.

Change-Id: I9f980e55d3d13f8fc16c410dc0d17dbdc200cb47
Reviewed-by: Juha Vuolle <juha.vuolle@qt.io>

1 files changed, 8 insertions, 1 deletions

diff --git a/tests/auto/corelib/kernel/qjniobject/testdata/src/org/qtproject/qt/android/testdata/QtJniObjectTestClass.java b/tests/auto/corelib/kernel/qjniobject/testdata/src/org/qtproject/qt/android/testdata/QtJniObjectTestClass.java
index dc55ad0f89..813aaf2bbf 100644
--- a/tests/auto/corelib/kernel/qjniobject/testdata/src/org/qtproject/qt/android/testdata/QtJniObjectTestClass.java
+++ b/tests/auto/corelib/kernel/qjniobject/testdata/src/org/qtproject/qt/android/testdata/QtJniObjectTestClass.java
@@ -170,5 +170,12 @@ public class QtJniObjectTestClass
     public static double[] staticDoubleArrayMethod()
     { double[] array = { 3.0, 2.0, 1.0 }; return array; }
     public double[] doubleArrayMethod() { return staticDoubleArrayMethod(); }
-}
 
+    // --------------------------------------------------------------------------------------------
+    native public int callbackWithObject(QtJniObjectTestClass that);
+
+    public int callMeBackWithObject(QtJniObjectTestClass that)
+    {
+        return callbackWithObject(that);
+    }
+}