NPE in javap

[Chen Liang]

Thanks for the report. This is known as https://bugs.openjdk.org/browse/JDK-8364095, and the proper modeling of preview features is pending on https://github.com/openjdk/jdk/pull/25017.

Chen
________________________________
From: valhalla-dev <valhalla-dev-retn at openjdk.org> on behalf of Remi Forax <forax at univ-mlv.fr>
Sent: Friday, August 8, 2025 5:53 PM
To: valhalla-dev <valhalla-dev at openjdk.org>
Subject: NPE in javap

This class throw an NPE in javap:

public value class RangeValue {
  private int min;
  private int max;

  public RangeValue(int a, int b) {
    if (a > b) {
      this.min = b;
      this.max = a;
    } else {
      this.min = a;
      this.max = b;
    }
    super();
  }

  public int min() {
    return min;
  }

  public int max() {
    return max;
  }
}


The stacktrace seems to say that ACC_STRICT (on fields) is not supported.

Rémi

---

bash-3.2$ $JAVA_HOME/bin/javap -c -verbose -private target/classes/RangeValue.class
Classfile /Users/forax/git/weather-alert/target/classes/RangeValue.class
  Last modified 9 Aug 2025; size 549 bytes
  SHA-256 checksum 10fcbe0722123c3576c1c9a4814180d3a436510b09c8308083b47b7bfe23d1bd
  Compiled from "RangeValue.java"
public final value class RangeValue
  minor version: 65535
  major version: 69
  flags: (0x0011) ACC_PUBLIC, ACC_FINAL
  this_class: #2                          // RangeValue
  super_class: #11                        // java/lang/Object
  interfaces: 0, fields: 2, methods: 3, attributes: 1
Constant pool:
   #1 = Fieldref           #2.#3          // RangeValue.min:I
   #2 = Class              #4             // RangeValue
   #3 = NameAndType        #5:#6          // min:I
   #4 = Utf8               RangeValue
   #5 = Utf8               min
   #6 = Utf8               I
   #7 = Fieldref           #2.#8          // RangeValue.max:I
   #8 = NameAndType        #9:#6          // max:I
   #9 = Utf8               max
  #10 = Methodref          #11.#12        // java/lang/Object."<init>":()V
  #11 = Class              #13            // java/lang/Object
  #12 = NameAndType        #14:#15        // "<init>":()V
  #13 = Utf8               java/lang/Object
  #14 = Utf8               <init>
  #15 = Utf8               ()V
  #16 = Utf8               (II)V
  #17 = Utf8               Code
  #18 = Utf8               LineNumberTable
  #19 = Utf8               LocalVariableTable
  #20 = Utf8               this
  #21 = Utf8               LRangeValue;
  #22 = Utf8               a
  #23 = Utf8               b
  #24 = Utf8               StackMapTable
  #25 = Utf8               ()I
  #26 = Utf8               SourceFile
  #27 = Utf8               RangeValue.java
{
Error: A serious internal error has occurred: java.lang.NullPointerException
Please file a bug report, and include the following information:
java.lang.NullPointerException
        at java.base/java.util.Objects.requireNonNull(Objects.java:318)
        at java.base/java.lang.reflect.AccessFlag$Location.findInHistory(AccessFlag.java:671)
        at java.base/java.lang.reflect.AccessFlag$Location.flagsMask(AccessFlag.java:707)
        at jdk.jdeps/com.sun.tools.javap.BasicWriter.maskToAccessFlagsReportUnknown(BasicWriter.java:66)
        at jdk.jdeps/com.sun.tools.javap.BasicWriter.flagsReportUnknown(BasicWriter.java:58)
        at jdk.jdeps/com.sun.tools.javap.ClassWriter.writeField(ClassWriter.java:437)
        at jdk.jdeps/com.sun.tools.javap.ClassWriter.writeFields(ClassWriter.java:428)
        at jdk.jdeps/com.sun.tools.javap.ClassWriter.write(ClassWriter.java:261)
        at jdk.jdeps/com.sun.tools.javap.JavapTask.write(JavapTask.java:859)
        at jdk.jdeps/com.sun.tools.javap.JavapTask.writeClass(JavapTask.java:684)
        at jdk.jdeps/com.sun.tools.javap.JavapTask.run(JavapTask.java:628)
        at jdk.jdeps/com.sun.tools.javap.JavapTask.run(JavapTask.java:474)
        at jdk.jdeps/com.sun.tools.javap.Main.main(Main.java:48)
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