IV16870: JAVA JIT - UNEXPECTED NULLPOINTEREXCEPTION

APAR status

• Closed as program error.

Error description

• Error Message: NullPointerException
  .
  Stack Trace:
  While not specific to the following code, we have seen a number
  of cases where the problem involed the following classes on the
  stack when the exception occurred: .
  
  at oracle.jdbc.driver.T4CTTIfun.receive(T4CTTIfun.java:290)
  at oracle.jdbc.driver.T4CTTIfun.doRPC(T4CTTIfun.java:191)
  
  (additional stack-frames may appear before or after the above
  lines)
  
  The problem does not exist in Java5. In most cases this problem
  will result in a
  NullPointerException. This is due to the fact that most
  constructors which initialize the same variable twice will first
  initialize to NULL then change it in a super class constructor
  to something non-null.
  

Local fix

• -Xjit:disableLookahead
  Note: Using this option will have a small effect on performance.
  

Problem summary

• The JIT fails to set-up correct aliasing information when
  inlining a constructor (<init>) method where the constructor
  calls a super class constructor and both constructors set the
  same class variable using different classes. i.e. B extends A, A
  has a field called 'var' but B does not define it's own 'var'.
  Therefore A.var and B.var both refer to the same variable. In
  this case there is the potential for the JIT to propagate the
  first initialization of A.var into later uses of A.var despite
  the fact that the variable is set to a new value using B.var
  before the use of A.var.
  

Problem conclusion

• This defect will be fixed in:
  6.0.1 SR1
  6.0.0 SR10
  .
  The JIT was modified to prevent this problem from occurring.
  

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

     UP

• R600 PSY

     UP