How Parameterized Slices Are Generated for Cobol Programs

The specifications for input and output parameters are:

• Input

  A variable of an arbitrary level from the LINKAGE section or PROCEDURE DIVISION USING is classified as an input parameter if one or more of its bits are used for reading before writing.

  A system variable (field of DFHEIB/DFHEIBLK structures) is classified as an input parameter if the Create CICS Program option is turned off and the variable is used for writing before reading.

• Output

  A variable of an arbitrary level from the LINKAGE section or PROCEDURE DIVISION USING is classified as an output parameter if it is modified during component execution.

  A system variable (a field of DFHEIB/DFHEIBLK structures) is classified as an output parameter if the Create CICS Program option is turned off and the variable is modified during component execution.

• For each input parameter, the algorithm finds its first usage (it does not have to be unique, the algorithm processes all of them), and if the variable (parameter from the LINKAGE section) is used for reading, code to copy its value from the corresponding field of BRE-INPUT-STRUCTURE is inserted as close to this usage as possible.
• The algorithm takes into account all partial or conditional assignments for this variable before its first usage and places PERFORM statements before these assignments.

  If a PERFORM statement can be executed more than once (as in the case of a loop), then a flag variable (named BRE-INIT-COPY-FLAG-[<n>] of the type PIC 9 VALUE 0 is created in the WORKING-STORAGE section, and the parameter is copied into the corresponding variable only the first time this PERFORM statement is executed.

• For all component exit points, the algorithm inserts code to copy all output parameters from working-storage variables to the corresponding fields of BRE-OUTPUT-STRUCTURE.

  Variables of any level (rather than only 01-level structures together with all their fields) can act as parameters. This allows exclusion of unnecessary parameters, making the resulting programs more compact and clear.

  For each operator for which a parameter list is generated, the following transformations are applied to the entire list:

  • All FD entries are replaced with their data descriptions.
  • All array fields are replaced with the corresponding array declarations.
  • All upper-level RENAMES clauses are replaced with the renamed declarations.
  • All upper-level REDEFINES clauses with an object (including the object itself, if it is present in the parameter list) are replaced with a clause of a greater size.
  • All REDEFINES and RENAMES entries of any level are removed from the list.
  • All variable-length arrays are converted into fixed-length of the corresponding maximal size.
  • All keys and indices are removed from array declarations.
  • All VALUE clauses are removed from all declarations.
  • All conditional names are replaced with the corresponding data items.