PH31333: At OPT(2), initialization for ODO item caching uses an incorrect stack offset, leading to an 0C4 using a null BLV cell

Obtain the fix for this APAR.

APAR status

• Closed as program error.

Error description

• To avoid some address recalculation for variably located items,
  the generated code caches OCCURS DEPENDING ON (ODO) item
  value(s) in ODOsv_cell(s); if the ODO item value(s) are
  unchanged at the point of access, the base locator for the
  variably located item (BLV) can be used as is, otherwise it
  needs to be recalculated.
  
  The ODOsv_cell's are supposed to be initially set to -1, so on
  the first reference to a variably located item, the BLV can be
  calculated for the first time.
  
  However, only with the COBOL 6.3 compiler at OPT(2), the
  compiler uses the wrong offset for the block of ODOsv_cell's and
  initializes some other area of memory, leaving the block of
  ODOsv_cell's zero, or containing some residual values. This can
  result in an 0C4 because
  
  * A BLV cell is never properly calculated. Updating the
    associated variably located item results in an invalid memory
    reference.
  
  * Depending on where the compile unit's stack frame is within a
    stack segment, the ODOsv_cell block initialization may write
    to unmapped memory.
  

Local fix

• Compile at OPT(1).
  

Problem summary

• ****************************************************************
  * USERS AFFECTED: Users of Enterprise COBOL 6.3 compiling      *
  *                 programs at OPT(1|2) that contain OCCURS 0   *
  *                 TO N TIMES DEPENDING ON X where the OCCURS   *
  *                 DEPENDING ON data item is first accessed     *
  *                 when the OCCURS DEPENDING ON object is 0.    *
  ****************************************************************
  * PROBLEM DESCRIPTION: Trying to access the OCCURS DEPENDING   *
  *                      ON data item accesses an invalid        *
  *                      memory address, leading to the wrong    *
  *                      memory being accessed and possibly to   *
  *                      the program abending with a S0C4.       *
  ****************************************************************
  * RECOMMENDATION: Apply the provided PTF.                      *
  ****************************************************************
  For every OCCURS DEPENDING ON data item, the compiler generates
  code to compute the address of the data item based on the value
  of the ODO object. To avoid recalculating the address when the
  ODO object hasn't changed, the compiler saves the value of the
  ODO object in a compiler-generated data item called an
  ODOsv_cell, and the address itself in a BLV_cell. The compiler
  was incorrectly initializing the ODOsv_cells. When an ODO
  address computation was needed, the uninitialized ODOsv_cells
  contained zero, and if the value of the ODO object at that time
  was also zero, the compiler skipped the address computation,
  using the value in the BLV_cell for the address. However, since
  the value in the BLV_cell was never computed, it was incorrect,
  and using it caused the generated code to access the wrong
  memory.
  

Problem conclusion

• The compiler was fixed to properly initialize the ODOsv_cells,
  causing the addresses in BLV_cells to be computed the first
  time they were needed even if the values of the ODO objects were
  zero.
  

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:

Modules/Macros

• IGY8RWTU IGYCASMB IGYCCBE  IGYCCCRT IGYCCICS IGYCCSRV IGYCDGEN
  IGYCDIAG IGYCDMAP IGYCEN$0 IGYCEN$1 IGYCEN$2 IGYCEN$3 IGYCEN$4
  IGYCEN$5 IGYCEN$8 IGYCEN$D IGYCEN$R IGYCFGEN IGYCFREE IGYCINIT
  IGYCJA$0 IGYCJA$1 IGYCJA$2 IGYCJA$3 IGYCJA$4 IGYCJA$5 IGYCJA$8
  IGYCJA$D IGYCJA$R IGYCLIBR IGYCLSTR IGYCLVL0 IGYCLVL1 IGYCLVL2
  IGYCLVL3 IGYCLVL8 IGYCMALL IGYCOSCN IGYCPGEN IGYCRCTL IGYCRDPR
  IGYCRDSC IGYCREAL IGYCRWT  IGYCSCAN IGYCSIMD IGYCUE$0 IGYCUE$1
  IGYCUE$2 IGYCUE$3 IGYCUE$4 IGYCUE$5 IGYCUE$8 IGYCUE$D IGYCUE$R
  IGYCXREF IGYDRV   IGYEQCWI IGYMSGE  IGYMSGK  IGYMSGT  IGYMSGXT
  IGYQCBE  IGYQSPLT IGYZQEN6 IGYZQENU IGYZQJP6 IGYZQJPN
  

Fix information

• Fixed component name

  ENT COBOL FOR Z

• Fixed component ID

  5655EC600

Applicable component levels

• R630 PSY UI72712

     UP20/11/28 P F011

• R631 PSY UI72713

     UP20/11/28 P F011

• R632 PSY UI72714

     UP20/11/28 P F011

Fix is available

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