IV78723: JAVA8 JIT X86: INCORRECT RETURN FROM CLASS.ISASSIGNABLEFROM()

APAR status

• Closed as program error.

Error description

• Error Message: A call to Class.isAssignableFrom() may return an
  invalid result on Java8 running on X86 hardware (i.e. Linux on
  AMD/Intel or Windows).
  .
  Stack Trace: N/A
  .
  The problem can only occur on Java8 and only a X86 hardware.
  Previous versions of Java and other hardware platforms are not
  effected by this problem
  

Local fix

• The problem can be avoid by setting the environment variable
  TR_disableInlineIsAssignableFrom=1 using the set command or the
  export command depending of the operating system.
  

Problem summary

• In Java8 the JIT would attempt to replace calls to
  class.isAssignableFrom() with an equivalent set of instructions
  but that sequence of code left the possibility that the result
  of the call could be incorrect.
  

Problem conclusion

• The JIT was modified so that isAssignableFrom() returns the
  correct results.
  .
  This APAR will be fixed in the following Java Releases:
     8    SR2       (8.0.2.0)
  .
  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

• R130 PSY

     UP