Computation Phase

PL/I Considerations › Using the Online Debugger with PL/I › Computation Phase

Computation Phase

Before beginning the debugging process, it is a good idea to determine the breakpoints you want to set and the storage locations you want to examine:

To determine the hexadecimal offset of an executable program instruction at which you wish to set a breakpoint, perform the following steps:

Examine the cross-reference table portion of your link-edit listing for an entry in the form program-name1. Record the hexadecimal offset listed under ORIGIN:

                        CROSS REFERENCE TABLE

  CONTROL SECTION                       ENTRY
    NAME    ORIGIN  LENGTH                NAME   LOCATION
  PLISTART      00      50
                                        PLICALLA       6
  PLIMAIN       50       8
  *PLIPROG2     58     394
  *PLIPROG1    3F0     EB4
                                        PLI3PROG     3F8
  IDMSPLI     12A8     284

Examine the PL/I compiler portion of your listing and record the line number of the statement at which you wish to set the breakpoint:

133                  WORK_LAST = EMP_LAST_NAME_0415;
134                  WORK_FIRST = EMP_FIRST_NAME_0415;
                                                              /*
                     MAP OUT (DCTEST01) OUTPUT DATA YES
                         MESSAGE (INITIAL_INSTRUCTIONS_MSG_1)
                         LENGTH (25)
                         DETAIL NEW KEY (DBKEY).
                                                              */
135                        /* IDMS PL/I DML EXPANSION */    DO;
136                        DML_SEQUENCE=0013;
137                        DCCFLG1=0;
138                        DCCFLG1=13;
139                        DCCFLG2=16;
140                        DCCFLG3=0;
141                        DCCFLG4=4;
142                        DCCFLG5=72;
143                        DCCFLG6=0;

Examine the Assembler listing generated by the LIST option, locate the previously recorded PL/I line number, and record its corresponding hexadecimal displacement value:

* STATEMENT NUMBER  136
0006AA  41 80 7 21C               LA    8,SUBSCHEMA_CTRL.D
                                        CCALIGN_AREA.FILLE
                                        R0001
0006AE  58 40 3 124               L     4,292(0,3)
0006B2  50 40 8 008               ST    4,SSC_ERRSAVE_AREA
                                        .DML_SEQUENCE

Add the origin offset and the breakpoint instruction's hexadecimal displacement to obtain the breakpoint address:
```
X'3F0' + X'6AA' = X'A9A'
```

To determine the offset of AUTOMATIC variables, locate the variable storage map and record the displacement value for each variable you wish to examine during the debugging process:

MAP_WORK_REC                       1          796       31C    AUTO

WORK_DEPT_ID                       1          796       31C    AUTO
WORK_EMP_ID                        1          800       320    AUTO
WORK_FIRST                         1          804       324    AUTO
WORK_LAST                          1          814       32E    AUTO
WORK_ADDRESS                       1          829       33D    AUTO
WORK_STREET                        1          829       33D    AUTO
WORK_CITY                          1          849       351    AUTO
WORK_STATE                         1          864       360    AUTO
WORK_ZIP                           1          866       362    AUTO
WORK_DEPT_NAME                     1          871       367    AUTO

You locate AUTOMATIC variables at run time through Register 13.

To determine the location of STATIC INTERNAL variables, examine the static internal storage map to find the hexadecimal offset for each variable you wish to examine during the debugging process.
You locate STATIC INTERNAL variables at run time through Register 3.