IJ20528: NULLPOINTEREXCEPTION OR SEGMENTATION FAULT FOR METHOD CALL TO OBJECT OF A PRIMITIVE WRAPPER TYPE

APAR status

• Closed as program error.

Error description

• Error Message: A segmentation fault might occur or a
  NullPointerException might be thrown for a call to a method of
  an object of one of the primitive wrapper types, such as
  java.lang.Integer, java.lang.Long, and so on, or to a method of
  an object of type java.lang.String.
  .
  Stack Trace: N/A
  .
  This problem was first introduced in IBM Java 8 SR5 FP31.
  

Local fix

• This issue can be worked around by specifying the option
  -Xjit:disableEscapeAnalysis.  Specifying this option might have
  an effect on program performance.
  

Problem summary

• One optimization of the Java JIT compiler is known as Escape
  Analysis.  Under this optimization, the compiler identifies Java
  objects whose duration is brief, and it allocates them on the
  run-time stack rather than the Java heap in order to improve the
  run-time performance of the program.  Such an object might be
  allocated on the run-time stack as a contiguous object, or if
  the entire object is not needed, as  several temporary variables
  for the individual instance members of the original object.
  In the cases of an object of type java.lang.String or an object
  of one of the wrapper class types for the Java primitive types,
  if that object has methods called on it, it might still be
  broken up into several temporary variables for its individual
  instance members by Escape Analysis.  Escape Analysis will
  generate code to allocate the object on the heap just at the
  point where one of its methods is called.
  Some calls to an object's method will happen through a pointer
  to the virtual function table for the object's class which is
  stored in a hidden instance member that is managed by the
  implementation.  In the problem case, Escape Analysis generated
  code to call a method that attempted to use a temporary variable
  for the pointer to the object's virtual function table, but that
  temporary variable was only initialized with a null pointer
  reference.
  

Problem conclusion

• The problem was fixed by ensuring that, for the kind of call
  described in the problem summary, Escape Analysis generates code
  that uses the pointer to the virtual function table that is a
  hidden instance member of the copy of the object that was
  allocated on the Java heap, rather than trying to use a separate
  temporary variable.  The pointer to the virtual function table
  that is part of the object that is allocated on the heap will
  always be initialized correctly.
  .
  This APAR will be fixed in the following Java Releases:
     8    SR6       (8.0.6.0)
  .
  Contact your IBM Product's Service Team for these Service
  Refreshes and Fix Packs.
  For those running stand-alone, information about the available
  Service Refreshes and Fix Packs can be found at:
             https://www.ibm.com/developerworks/java/jdk/
  

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