Feedback on LW1 EAR

[Uberto Barbini]

Good morning,


I've played a bit in these days with the EAR and here is my feedback.

First of all, thanks for the great work! It's really nice to be able to use
ValueTypes for immutable small objects.

We the London Java Community we are organizing a hack day on this for
middle of September, if someone is interested.

Now I've a few question and a fatal error to report.

1) I saw there I can create Value Types using makeDefault + setField in a
static method or I can use the "normal" new Value() syntax?
The byte code produced seems identical:
4 invokestatic #3 <com/gamasoft/Point.$makeValue$>
Is there a difference or a preference for the future?

2) Currently == won't compile. It will work eventually? It would be nice to
be able to control a few of operator (== + - * / say)...

3) in the declaration
final __ByVal public class
final seems to be optional. Will it stay so?

4) isValue() is still not present, is there another way to know if an
instance or a class is a Value or not with current EAR?

5) I saw that I can override toString() and call super.toString() to have
the standard Object behavior. I wonder if there will be some kind of base
class for all ValueTypes or not.


Then I've tried to replace some immutable classes into Value Types use them
in my other projects.
The main hindrance has been the missing support for generics.
As workaround I've created a interface and based the collection on the
interface. It worked in a few projects but I had a Fatal Error on a simple
algorithm. I've tried to understand the exact problem but the same code
seems to work as standalone project... If it's something worth
investigating I can dig it more

https://github.com/uberto/eopi/blob/ValhallaLW01/src/test/java/com/gamasoft/eopi/cap17_DynamicProgramming/KnapsackTest.java


#
# A fatal error has been detected by the Java Runtime Environment:
#
#  SIGSEGV (0xb) at pc=0x00007f08c3d648aa, pid=18399, tid=18426
#
# JRE version: OpenJDK Runtime Environment (11.0) (build
11-lworldea+0-2018-07-30-1734349.david.simms.valhalla)
# Java VM: OpenJDK 64-Bit Server VM
(11-lworldea+0-2018-07-30-1734349.david.simms.valhalla, mixed mode,
compressed oops, g1 gc, linux-amd64)
# Problematic frame:
# V  [libjvm.so+0x4148aa]  AddPNode::Value(PhaseGVN*) const+0x7a
#
# No core dump will be written. Core dumps have been disabled. To enable
core dumping, try "ulimit -c unlimited" before starting Java again
#
# If you would like to submit a bug report, please visit:
#   http://bugreport.java.com/bugreport/crash.jsp
#

---------------  S U M M A R Y ------------

Command Line: -ea -XX:+EnableValhalla
-Didea.test.cyclic.buffer.size=1048576
-javaagent:/home/uberto/idea-IC-181.4203.550/lib/idea_rt.jar=35303:/home/uberto/idea-IC-181.4203.550/bin
-Dfile.encoding=UTF-8 com.intellij.rt.execution.junit.JUnitStarter
-ideVersion5 -junit4
com.gamasoft.eopi.cap17_DynamicProgramming.KnapsackTest,bigShop

Host: Intel(R) Core(TM) i7-4750HQ CPU @ 2.00GHz, 8 cores, 15G, Ubuntu
16.04.4 LTS
Time: Sat Aug 18 11:05:34 2018 BST elapsed time: 0 seconds (0d 0h 0m 0s)

---------------  T H R E A D  ---------------

Current thread (0x00007f0880159800):  JavaThread "C2 CompilerThread1"
daemon [_thread_in_native, id=18426,
stack(0x00007f089c2f5000,0x00007f089c3f6000)]


Current CompileTask:
C2:    805  250
com.gamasoft.eopi.cap17_DynamicProgramming.Knapsack$WatchV::equals (8 bytes)

Stack: [0x00007f089c2f5000,0x00007f089c3f6000],  sp=0x00007f089c3f1f10,
 free space=1011k
Native frames: (J=compiled Java code, A=aot compiled Java code,
j=interpreted, Vv=VM code, C=native code)
V  [libjvm.so+0x4148aa]  AddPNode::Value(PhaseGVN*) const+0x7a
V  [libjvm.so+0xc95769]  PhaseGVN::transform_no_reclaim(Node*)+0x49
V  [libjvm.so+0xc750b5]  Parse::optimize_cmp_with_klass(Node*)+0x125
V  [libjvm.so+0xc7c6c8]  Parse::do_one_bytecode()+0x3f28
V  [libjvm.so+0xc6aa78]  Parse::do_one_block()+0x218
V  [libjvm.so+0xc6aea3]  Parse::do_all_blocks()+0xc3
V  [libjvm.so+0xc6cf60]  Parse::Parse(JVMState*, ciMethod*, float)+0x940
V  [libjvm.so+0x561968]  ParseGenerator::generate(JVMState*)+0x78
V  [libjvm.so+0x749360]  Parse::do_call()+0x2c0
V  [libjvm.so+0xc7c4a4]  Parse::do_one_bytecode()+0x3d04
V  [libjvm.so+0xc6aa78]  Parse::do_one_block()+0x218
V  [libjvm.so+0xc6aea3]  Parse::do_all_blocks()+0xc3
V  [libjvm.so+0xc6cf60]  Parse::Parse(JVMState*, ciMethod*, float)+0x940
V  [libjvm.so+0x561968]  ParseGenerator::generate(JVMState*)+0x78



---class code


    interface Watch{ //mini interface for use with generics
        int weight();
        int price();
    }


    __ByValue public static class WatchV implements Watch {
        public final int weight;
        public final int price;

        public WatchV(int weight, int price) {
            this.weight = weight;
            this.price = price;
        }

        @Override
        public String toString() {
            return "W{"+ weight +
                    "," + price +
                    '}';
        }

        @Override
        public int weight() {
            return weight;
        }

        @Override
        public int price() {
            return price;
        }
    }