Hi Paul, Alan,

I incorporated Paul's suggestions into new webrev:


This iteration also contains a nearly-exhaustive test of Class.getMethods(): PublicMethodsTest. It is actually a test generator. Given a Case template, it generates all variants of methods for each of the types in the case. Case1 contains 4 interface method variants ^ 3 interfaces * 4 class method variants ^ 3 classes = 4^6 = 4096 different sub-cases of which only 1379 compile. The results of those 1379 sub-cases are persisted in the Case1.results file. Running the test compares the persisted results with actual result of executing each sub-case. When running this test on plain JDK 9 (without patch), the test finds 218 sub-cases where results differ:


Looking at those differences gives the impression of the effects of the patch.

Regards, Peter

On 10/11/2016 11:35 PM, Paul Sandoz wrote:
Hi Peter,

Nice work here.


I would be inclined to change PublicMethods to encapsulate an instance of LinkedHashMap, since it’s only the consolidate/toArray methods that really matter, and no need for the key/value types to be exposed, then no need to declare serialVersionUID, and also it can be final. The JavaDoc on consolidate would need to be tweaked.

   29      * existing methods with same signature if they are less specific 
then added

   89             if (o == null || getClass() != o.getClass()) return false;

Could be simplified to

  if (!(o instanceof Key)) return false


On 4 Oct 2016, at 06:40, Peter Levart <peter.lev...@gmail.com <mailto:peter.lev...@gmail.com>> wrote:


I have a fix for conformance (P2) bug (8062389 <https://bugs.openjdk.java.net/browse/JDK-8062389>) that also fixes a conformance (P3) bug (8029459 <https://bugs.openjdk.java.net/browse/JDK-8029459>) and a performance issue (8061950 <https://bugs.openjdk.java.net/browse/JDK-8061950>):

http://cr.openjdk.java.net/~plevart/jdk9-dev/Class.getMethods.new/webrev.04/ <http://cr.openjdk.java.net/%7Eplevart/jdk9-dev/Class.getMethods.new/webrev.04/>

As Daniel Smith writes in 8029459 <https://bugs.openjdk.java.net/browse/JDK-8029459>, the following situation is as expected:

interface I { void m(); }
interface J extends I { void m(); }
interface K extends J {}
K.class.getMethods() = [ J.m ]

But the following has a different result although it should probably have the same:

interface I { void m(); }
interface J extends I { void m(); }
interface K extends I, J {}
K.class.getMethods() = [ I.m, J.m ]

He then suggests the following algorithm:

An implementation of getMethods consistent with JLS 8 would include the following (see Lambda Spec, Part H, 9.4.1 and 8.4.8):
1) The class's/interface's declared (public) methods
2) The getMethods() of the superclass (if this is a class), minus any that have a match in (1) 3) The getMethods() of each superinterface, minus any that have a match in (1) or a _concrete_ match in (2) or a match from a more-specific class/interface in (2) or (3)

But even that is not sufficient for the following situation:

interface E { void m(); }
interface F extends E { void m(); }
abstract class G implements E {}
abstract class H extends G implements F {}
H.class.getMethods() = [ E.m, F.m ]

The desired result of H.class.getMethods() = [ F.m ]

So a more precise definition is required which is implemented in the fix.

The getMethods() implementation partitions the union of the following methods:

1) The class's/interface's declared public methods
2) The getMethods() of the superclass (if this is a class)
3) The non-static getMethods() of each direct superinterface

...into equivalence classes (sets) of methods with same signature (return type, name, parameter types). Within each such set, only the "most specific" methods are kept and others are discarded. The union of the kept methods is the result.

The "more specific" is defined as a partial order within a set of methods of same signature:

Method A is more specific than method B if:
- A is declared by a class and B is declared by an interface; or
- A is declared by the same type as or a subtype of B's declaring type and both are either declared by classes or both by interfaces (clearly if A and B are declared by the same type and have the same signature, they are the same method)

If A and B are distinct elements from the set of methods with same signature, then either:
- A is more specific than B; or
- B is more specific than A; or
- A and B are incomparable

A sub-set of "most specific" methods are the methods from the set where for each such method M, there is no method N != M such that N is "more specific" than M.

There can be more than one "most specific" method for a particular signature as they can be inherited from multiple unrelated interfaces, but: - javac prevents compilation when among multiply inherited methods with same signature there is at least one default method, so in practice, getMethods() will only return multiple methods with same signature if they are abstract interface methods. With one exception: bridge methods that are created by javac for co-variant overrides are default methods in interfaces. For example:

   interface I { Object m(); }
   interface J1 extends I { Map m(); }
   interface J2 extends I { HashMap m(); }
   interface K extends J1, J2 {}

K.class.getMethods() = [ default Object j1.m, abstract Map j1.m, default Object j2.m, abstract HashMap j2.m ]

But this is an extreme case where one can still expect multiple non-abstract methods with same signature, but different declaring type, returned from getMethods().

In order to also fix 8062389 <https://bugs.openjdk.java.net/browse/JDK-8062389>, getMethod() and getMethods() share the same consolidation logic that results in a set of "most specific" methods. The partitioning in getMethods() is partially performed by collecting Methods into a HashMap where the keys are (name, parameter types) tuples and values are linked lists of Method objects with possibly varying return and declaring types. The consolidation, i.e. keeping only the set of most specific methods as new methods are encountered, is performed only among methods in the list that share same return type and also removes duplicates. getMethod() uses only one such list, consolidates methods that match given name and parameter types and returns the 1st method from the resulting list that has the most specific return type.

That's it for algorithms used. As partitioning partially happens using HashMap with (name, parameter types) keys, lists of methods that form values are typically kept short with most of them containing only a single method, so this fix also fixes performance issue 8061950 <https://bugs.openjdk.java.net/browse/JDK-8061950>.

The patch also contains some optimizations around redundant copying of arrays and reflective objects.

The FilterNotMostSpecific jtreg test has been updated to accommodate for changed behavior. Both of the above extreme cases have been added to the test.

So, comments, please.

Regards, Peter

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