IV22237: REFLECTIVE FIELD MODIFICATION LEADS TO INCORRECT METHOD CALLS

APAR status

• Closed as program error.

Error description

• Error Message: When a base class B is extended by a subclass C
  and one of its public methods M is overridden, a call to C.M can
  incorrectly execute B.M, when the following conditions are met:
  - a third class defines F as a private static field of type B;
  - the field is modified by external code, via reflection, to
  point to an object of type C;
  - F.M is called in a hot loop.
  .
  Stack Trace: N/A
  .
  

Local fix

• This problem can be avoided by setting the JVM command-line
  option -Xjit:disablelookahead.
  

Problem summary

• The JIT compiler attempted to optimize the hot call by
  devirtualizing the call to M, but its analysis resulted in an
  incorrect type for the private static field F when it could be
  modified via reflection.
  

Problem conclusion

• This defect will be fixed in:
  6.0.1 SR3
  7.0.0 SR2
  6.0.0 SR11
  5.0.0 SR13FP2
  .
  The JIT compiler has been updated to perform the type analysis
  correctly.
  

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:

  IV22238 PM66904

Fix information

• Fixed component name

  JIT

• Fixed component ID

  620700124

Applicable component levels

• R260 PSY

     UP

• R600 PSY

     UP