PH68254: A LOOP WITH A GOTO STATEMENT EXECUTES MORE TIMES THAN EXPECTED AT OPT(2)

Obtain the fix for this APAR.

APAR status

• Closed as program error.

Error description

• Users of Enterprise COBOL 6.x compiling programs at OPT(2) that
  include a GO TO statement working with a BINARY/COMP/COMP-4 data
  item serving as a loop counter which increments or decrements by
  1 each iteration where the initial value of the loop counter is
  at or outside the bounds for the loop.
  
  The compiler optimizes the loop to count down to 0 and generates
  an instruction that decrements the loop counter, compares it to
  zero, and branches to the top of the loop if non-zero. If the
  initial value of the counter is at or exceeding the loop bounds,
  it will be transformed to be 0 or negative, and decrementing the
  counter means it's definitely negative, so the loop continues to
  execute until the counter wraps around and eventually reaches 1,
  decrementing to 0, allowing the loop to finally terminate.
  

Local fix

• Compile with OPT(0|1)
  

Problem summary

• ****************************************************************
  * USERS AFFECTED: Users of Enterprise COBOL 6.5 compiling      *
  *                 programs at OPT(2) that include a GO TO      *
  *                 statement working with a BINARY/COMP/COMP-4  *
  *                 data item serving as a loop counter which    *
  *                 increments or decrements by 1 each           *
  *                 iteration where the initial value of the     *
  *                 loop counter is at or outside the bounds     *
  *                 for the loop.                                *
  ****************************************************************
  * PROBLEM DESCRIPTION: Loop executes many more times than      *
  *                      expected.                               *
  ****************************************************************
  * RECOMMENDATION: Apply the provided PTF                       *
  ****************************************************************
  The compiler optimizes the loop to count down to 0 and
  generates an instruction that decrements the loop counter,
  compares it to zero, and branches to the top of the loop if
  non-zero. If the initial value of the counter is at or
  exceeding the loop bounds, it will be transformed to be 0 or
  negative, and decrementing the counter means it's definitely
  negative, so the loop continues to execute until the counter
  wraps around and eventually reaches 1, decrementing to 0,
  allowing the loop to finally terminate.
  

Problem conclusion

• The compiler was fixed to avoid the optimization in cases
  where it can't ensure the initial value of the loop counter is
  within the loop bounds.
  

Temporary fix

Comments

APAR Information

• APAR is sysrouted FROM one or more of the following:

  PH67073

• 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 IGYCJBLD IGYCJDMJ IGYCJDNJ IGYCJGEN IGYCLIBR
  IGYCLSTR IGYCLVL0 IGYCLVL1 IGYCLVL2 IGYCLVL3 IGYCLVL8 IGYCMALL
  IGYCOB2  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  IGYQCBE  IGYQSPLT IGYZQEN6
  IGYZQENU IGYZQJP6 IGYZQJPN
  

Fix information

• Fixed component name

  ENT COBOL FOR Z

• Fixed component ID

  5655EC600

Applicable component levels

• R650 PSY UO05070

     UP25/10/01 P F509

• R651 PSY UO05071

     UP25/10/01 P F509

• R652 PSY UO05072

     UP25/10/01 P F509

• R65H PSY UO05073

     UP25/10/01 P F509

Fix is available

• Select the PTF appropriate for your component level. You will be required to sign in. Distribution on physical media is not available in all countries.