IV49646: SYNCHRONIZED METHOD IN SUB-CLASS FAILS TO OVERRIDE SAME METHOD I N SUPER-CLASS

APAR status

• Closed as program error.

Error description

• Error Message: An unexpected exception (e.g.
  java.lang.reflect.InvocationTargetException) is thrown by a Java
  program in which one class extends another and overrides one of
  its methods with a synchronized version, e.g.
  class Parent {
    public void foo() {
      ...
    }
  }
  class Child extends Parent {
    public synchronized void foo() {
      super.foo();
    }
  }
  .
  Stack Trace: N/A
  .
  

Local fix

• Explicitly synchronizing within the overriding method will avoid
  the exception, e.g.
  public synchronized void foo() {
    synchronized (this) {
      super.foo();
    }
  }
  

Problem summary

• The problem is caused by the JIT compiler which fails to
  consider all method modifiers when determining whether a method
  in a sub-class has overridden any method in the super-classes.
  If it draws the wrong conclusion and then compiles such methods,
  or inlines them into their callers, the method in the
  super-class will appear to be non-overridden, which can lead to
  various incorrect behaviours in the program, such as throwing an
  InvocationTargetException.
  

Problem conclusion

• This defect will be fixed in:
  7.0.0 SR6
  6.0.1 SR7
  .
  The JIT compiler has been updated to check all modifiers on
  methods when an sub-class is loaded.
  

Temporary fix

Comments

APAR Information

• APAR is sysrouted FROM one or more of the following:

• APAR is sysrouted TO one or more of the following:

Fix information

• Fixed component name

  JIT

• Fixed component ID

  620700124

Applicable component levels

• R260 PSY

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