Hi,
I think Daniel is talking about the "dispatch" semantics of
unreflectSpecial here, right Daniel?
The findSpecial / unreflectSpecial is a MethodHandle equivalent for
bytecode instruction invokespecial (sans actual invoking). invokespecial
is typically used for implementing the super.method(args) Java
invocations. In that case, the superclass method is targeted - this is
not a virtual method dispatch like aMethod.invoke(this, arg*) - i.e. the
reflective invocation is always a virtual invocation (for non-private
methods). Likewise findSpecial and unreflectSpecial produce a
MethodHandle that dispatches to the method in the superclass (the
aMethod.getDeclatingClass() in case of unreflectSpecial) regardless of
whether that method is overridden in the subclass or not.
Regards, Peter
On 7/30/19 4:47 PM, Mandy Chung wrote:
Think about aMethod is a protected method inherited from its
superclass T. To invoke aMethod, the receiver must be an instance of
T or a subclass of T.
Mandy
On 7/30/19 3:22 AM, Daniel Fuchs wrote:
Hi Mandy,
380 * <th scope="row">{@link
java.lang.invoke.MethodHandles.Lookup#unreflectSpecial
lookup.unreflectSpecial(aMethod,this.class)}</th>
381 * <td>{@code T m(A*);}</td><td>{@code (T)
aMethod.invoke(this, arg*);}</td>
Is this exactly true? I mean - if `this` is an instance of
a subclass of `aMethod.getDeclaringClass()`, and if that
subclass overrides `aMethod`, then I would expect
`aMethod.invoke(this, arg*)` to execute the bytecode
of the method defined in the subclass.
If I'm not mistaken, the test does expect that the
bytecode in the super class is executed instead.
I suspect that `unreflectSpecial` can only be specified
in terms of `findSpecial`. But maybe I'm missing something.
I'm not too familiar with the intricacies of MethodHandle.
best regards,
-- daniel
On 26/07/2019 18:41, Mandy Chung wrote:
Daniel noticed that `unreflectSpecial` is missing in the "Lookup
Factory Methods" section in the class spec. In fact there are a
duplicated `lookup.unreflect(aMethod)` row that might originally be
for `unreflectSpecial`. I fix the javadoc in this patch:
http://cr.openjdk.java.net/~mchung/jdk14/8209005/webrev.01/
Mandy
On 7/25/19 1:12 PM, Mandy Chung wrote:
This patch fixes Lookup.unreflectSpecial to pass the declaring
class of Method being unreflected (rather than null) so that it can
accurately check if the special caller class is either the lookup
class or a superinterface of the declaring class.
Webrev:
http://cr.openjdk.java.net/~mchung/jdk14/8209005/webrev.00/index.html
The test runs in both unnamed module and named module to cover
JDK-8209078 which has been resolved by JDK-8173978.
thanks
Mandy
