Sample PL/I Online Debugger Session

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Sample PL/I Online Debugger Session

To use the online debugger with a DC/UCF PL/I program, perform the following steps:

Compile the program with the LIST, OFFSET, XREF STORAGE, and MAP compiler options before defining it to the DC/UCF system.
Record breakpoint and storage displacements, as explained above.
Initiate the debugger session by entering the DEBUG task code from the DC/UCF system. The DEBUG> prompt displays indicating that the debugger is in control:
```
ENTER NEXT TASK CODE:
debug

DEBUG>
```
Specify the program to be debugged by entering DEBUG followed by the program name. The debugger verifies the program name:
```
DEBUG>
debug pliprog

DEBUG PLIPROG
DEBUG> DEBUGGING INITIATED FOR PLIPROG VERSION 1
DEBUG>
```
Establish breakpoints by issuing the AT command followed by a dollar sign, which signifies the address of the beginning of the program; follow the dollar sign with the command's hexadecimal offset. The debugger verifies the establishment of the breakpoint:
```
DEBUG>
at $ + @a9a

AT @A9A
AT> @A9A ADDED
DEBUG>
```
After all breakpoints have been set, leave the setup phase of the debugger session by issuing the EXIT command:
```
DEBUG>
exit
```
Initiate the runtime phase by issuing the task code that invokes the task in which the program participates:
```
ENTER NEXT TASK CODE:
deptmod
```
When a breakpoint is encountered at runtime, the debugger assumes control and identifies the address, program, and the debugger expression that was used to establish the breakpoint:
```
AT OFFSET @A9A IN PLIPROG EXPRESSION @BDE
DEBUG>
```
Examine program variable storage by issuing LIST commands. Use indirect addressing and the previously noted register and offset:
```
list %:r13 + @31c 32

LIST %:R13 + @31C 32
001DB7F4  F3F2F0F0 F0F0F0F4 C8C5D9C2 C5D9E340 *32000004HERBERT*
001DB804  4040C3D9 C1D5C540 40404040 40404040 *  CRANE        *
```
If your program contains any nested procedures or begin blocks, you will need to navigate the chain of dynamic storage areas (DSAs) to obtain the correct variable-storage base address. To navigate the DSA chain for nested procedures or begin blocks, list the contents of register 13 to determine the DSA for the current level of nesting:
```
list %:r13

LIST %:R13
001C7A30  84200000 001C7948 00000000 5E422A20 *D...........
...*
```
For subsequent levels of nesting, perform the following steps:
1. List the absolute address which is located 4 bytes off of the previously displayed line:
```
list @1c7948

LIST @1C7948
001C7948  84200000 001C74D8 00000000 4E4227EC *D......Q....+...*
```
2. List AUTOMATIC variable-storage values after the final level of nesting has been reached. Use the absolute address as the base address, which is located 4 bytes off of the display:
```
DEBUG>
list 1c74d8 + @31c 32

LIST 1C74D8 + @31C 32
001C77F4  F3F2F0F0 F0F0F0F4 C8C5D9C2 C5D9E340 *32000004HERBERT *
001C7804  4040C3D9 C1D5C540 40404040 40404040 *  CRANE         *
```
To examine variables defined as BASED storage, perform the following steps:
1. List the contents of the associated pointer variable using indirect addressing:
```
DEBUG>
list %:r13 + @d4

LIST %:R13 + @D4
001499E0  00149AC8 00000000 00000000 00000000 *...H............*
```
2. List the absolute address to display the BASED variable's values:
```
DEBUG>
LIST @149ac8 16
00149AC8  F1F1F1F1 C4C5D7E3 00000000 00000000 *1111DEPT........*
```
Enter the RESUME command from the DEBUG> prompt to continue program execution:
```
DEBUG>
resume
```
Enter the QUIT command from the DEBUG> prompt to end a debugger session:
```
DEBUG>
quit

QUIT
QUIT DEBUGGER
ENTER NEXT TASK CODE:
```