IV91275: INCORRECT RESULTS CONVERTING BYTE TO CHAR ARRAY

APAR status

• Closed as program error.

Error description

• Error Message: Incorrect output or unexpected behaviour possibly
  resulting in an unexpected exception being thrown or a crash.
  .
  Stack Trace: N/A
  .
  On the x86 and POWER platforms, only Java 7R1 and Java 8 are
  affected. On z Systems all releases mentioned below are
  affected.
  

Local fix

• The issue can be avoided using the following Java option:
  -Xjit:disableIdiomRecognition
  or, if available,
  -Xjit:disableIdiomPatterns={CopyingTROx(*)}
  These options may have some performance impact, but they can be
  restricted to the problematic method to limit that if necessary.
  

Problem summary

• The JIT compiler may try to optimize loops which read from a
  byte array and write to a char array. If this is optimization is
  performed, then incorrect results can be produced in one of the
  following ways:
  - If the loop should produce as output the sign-extension of
  each input byte, the output produced might instead be the
  zero-extension.
  - If the loop should add an offset to each value, the output
  produced might not include the offset.
  - On x86 and POWER platforms, if the loop should exit early for
  some byte values but not others, the loop might exit too early.
  

Problem conclusion

• The JIT compiler has been updated to prevent the scenarios
  mentioned above from occurring.
  .
  This APAR will be fixed in the following Java Releases:
   7 R1 SR4 (7.1.4.0)
   8 SR4 (8.0.3.22)
   6 SR16 FP40 (6.0.16.40)
   6 R1 SR8 FP40 (6.1.8.40)
   7 SR10 (7.0.10.0)
  .
  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:

• Fixed component name

  JIT

• Fixed component ID

  620700124

Applicable component levels

• R130 PSY

     UP

• R600 PSY

     UP

• R260 PSY

     UP