IJ54756: UNEXPECTED BEHAVIOUR WITH VERY LARGE ARRAYS

APAR status

• Closed as program error.

Error description

• Error Message: In the only reported case the problem surfaced as
  an unexpected java.lang.NegativeArraySizeException resulting
  from calling ArrayList.addAll for two very large ArrayList
  objects. However it is possible that other errors could arise
  when dealing with very large arrays.
  .
  Stack Trace: N/A
  .
  

Local fix

• The problem stems from incorrect behaviour of the globalVP
  optimisation. If a specific method can be identified then the
  optimisation can be disabled for just that method, e.g.
  -Xjit:'dontInline={java/util/ArrayList.newCapacity(I)I},{java/ut
  il/ArrayList.newCapacity(I)I}(disableGlobalVP)'
  Otherwise it can be disabled globally, but at a greater impact
  to performance:
  -Xjit:disableGlobalVP
  

Problem summary

• The globalVP optimisation incorrectly used too small a value for
  the upper limit of an array size. When this incorrect value was
  used to check if code paths could be executed it came to the
  wrong conclusion and removed a conditional and part of the code
  block that it guarded. As a result an integer used as an array
  index wrapped negative and triggered the exception.
  

Problem conclusion

• The globalVP optimisation has been updated to use the correct
  upper bound for array sizes.
  https://github.com/eclipse-omr/omr/pull/7696
  .
  This APAR will be fixed in the following Releases:
  .
  IBM Semeru Runtimes
     21              21.0.7.0
     17              17.0.15.0
     11              11.0.27.0
  IBM SDK, Java Technology Edition
     8    SR8 FP50  (8.0.8.50)
  .
  Downloads and supplementary documentation can be found at the
  following locations:
  - For non z/OS operating systems:
    - IBM Semeru Runtimes, Version 11 and later
      https://www.ibm.com/semeru-runtimes/downloads/
    - IBM SDK, Java Technology Edition, Version 8
      https://www.ibm.com/support/pages/java-sdk-downloads/
  - For the z/OS operating system:
    - Java SDK Products on z/OS
      https://www.ibm.com/support/pages/java-sdk-products-zos
  

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