Document revision date: 30 March 2001

The .MAP file for the sample program is shown in Example B-3. Only the Program Section Synopsis with the psect, module, base address, end address, and length are listed.

Example B-3 .MAP File for the Sample Program

+--------------------------+ ! Program Section Synopsis ! +--------------------------+ Psect Name Module Name Base End Length ---------- ----------- ---- --- ------ $LINKAGE 00010000 000100FF 00000100 ( 256.) LOG 00010000 000100FF 00000100 ( 256.) $LITERAL 00010100 00010158 00000059 ( 89.) LOG 00010100 00010158 00000059 ( 89.) $READONLY 00010160 00010160 00000000 ( 0.) LOG 00010160 00010160 00000000 ( 0.) $INIT 00020000 00020000 00000000 ( 0.) LOG 00020000 00020000 00000000 ( 0.) $UNINIT 00020000 0002002F 00000030 ( 48.) LOG 00020000 0002002F 00000030 ( 48.) $CODE 00030000 0003027B 0000027C ( 636.) LOG 00030000 0003027B 0000027C ( 636.)

The DELTA debug session is shown in Example B-4.

Example B-4 DELTA Debugging Session of the Sample Program

$ DEFINE LIB$DEBUG SYS$LIBRARY:DELTA (1) $ RUN/DEBUG LOG (2) Alpha/VMS DELTA Version 1.5 (3) Brk 0 at 00030200 00030200! LDA SP,#XFFD0(SP) 30000,1;X X1 164! CMPEQ R0,#X14,R16 .;B (4) X1 1AC! BSR R26,#XFFFF94 .;B (5) ;P Brk 1 at 00030164 (6) X1+00000164! CMPEQ R0,#X14,R16 R0/ 00000001 ;P Brk 2 at 000301AC X1+000001AC! BSR R26,#XFFFF94 O PID= 00000021 PRCNAM= SWAPPER LOGINTIM= 00:00:00.00 (7) X1+000001B0! BR R31,#XFFFFE1 ;P Brk 1 at 00030164 X1+00000164! CMPEQ R0,#X14,R16 R0/ 00000001 ;P Brk 2 at 000301AC X1+000001AC! BSR R26,#XFFFF94 O (8) PID= 00000024 PRCNAM= ERRFMT LOGINTIM= 16:24:01.03 X1+000001B0! BR R31,#XFFFFE1 ;P Brk 1 at 00030164 X1+00000164! CMPEQ R0,#X14,R16 ;B 1 00030164 2 000301AC 0,1;B ;B 2 000301AC ;P Brk 2 at 000301AC (9) X1+000001AC! BSR R26,#XFFFF94 O PID= 00000025 PRCNAM= OPCOM LOGINTIM= 16:24:02.56 X1+000001B0! BR R31,#XFFFFE1 ;P Brk 2 at 000301AC (10) X1+000001AC! BSR R26,#XFFFF94 O PID= 00000026 PRCNAM= AUDIT_SERVER LOGINTIM=16:24:03.66 X1+000001B0! BR R31,#XFFFFE1 ;P Brk 2 at 000301AC (11) X1+000001AC! BSR R26,#XFFFF94 X1 84! LDQ R16,#X0040(R2) [Linefeed] (12) X1+00000088! LDL R18,#X0010(FP) [Linefeed] X1+0000008C! JSR R26,(R26) .;B (13) ;B 1 0003008C 2 000301AC ;P (14) Brk 1 at 0003008C (15) X1+0000008C! JSR R26,(R26) O PID= 00000027 PRCNAM= JOB_CONTROL LOGINTIM= 16:24:06.83 X1+00000090! BIS R31,FP,SP ;P Brk 2 at 000301AC X1+000001AC! BSR R26,#XFFFF94 ;P Brk 1 at 0003008C (16) X1+0000008C! JSR R26,(R26) O PID= 00000028 PRCNAM= NETACP LOGINTIM= 16:24:22.86 X1+00000090! BIS R31,FP,SP ;P Brk 2 at 000301AC X1+000001AC! BSR R26,#XFFFF94 ;B 1 0003008C 2 000301AC 0,2;B 0,1;B ;B ;P PID= 00000029 PRCNAM= EVL LOGINTIM= 16:24:26.67 PID= 0000002A PRCNAM= REMACP LOGINTIM= 16:24:38.21 PID= 0000002B PRCNAM= LATACP LOGINTIM= 16:24:43.18 PID= 0000004C PRCNAM= GODDARD LOGINTIM= 07:40:49.34 PID= 0000002D PRCNAM= SYMBIONT_0001 LOGINTIM= 16:25:47.54 PID= 0000002F PRCNAM= MCCORMICK LOGINTIM= 16:27:45.27 Exit 00000001 8002228C! ADDL R15,SP,SP EXIT

1. DELTA is enabled as the debugger.
2. The example program LOG is invoked with DELTA.
3. DELTA displays a version number and the first executable instruction. The base address of the program (determined from the map file) is virtual address 30000. The base address is placed in base register 1 with ;X. Now references to an address can use the address offset notation. For example, a reference to the first instruction is X1+200 (or the base address 30000 + offset 200). Also, DELTA displays some address locations as offsets to the base address.
4. The instruction at address 30164 is displayed in instruction mode using !. Its address location is expressed as the base address plus an offset. In the listing file, the offset is 164. (This is the point where the return status from SYS$GETJPIW is checked.) The base address in base address register X1 is 30000. The address reference, then, is X1+164. Note the + sign is implied when not specified.
   A simple breakpoint is set at that address using the ;B command. The address reference for ;B is the . symbol, representing the current address. X1+164;B would have done the same thing.
5. The same commands (! command to view the instruction and ;B to set a breakpoint) are repeated for the instruction at offset 1AC. (This is the point at which the print_line function is called.)
6. Program execution halts at the first breakpoint. DELTA displays the breakpoint message (Brk 1 at 00030164) with the breakpoint number 1 and the virtual address. The virtual address is 30164, which is the base address (30000) plus the offset 164. DELTA then displays the instruction in instruction mode (CMPEQ R0,#X14,R16). The contents of the general register 0 are displayed with the / command. DELTA displays the contents of R0, which is 1. Program execution continues using the ;P command.
7. The function print_line is executed, and the output (PID, process name, and login time) is displayed.
8. The O command halts program execution at the instruction where the function returns control (BR R31,#XFFFFE1). (This is the point at which control passes to checking the conditions of the while loop.) Program execution continues with ;P.
9. Breakpoint 2 is encountered. DELTA displays the breakpoint message, and the instruction. The function is executed with the O command and the function output is displayed. The next instruction where the function returns control is displayed. Program execution continues with the ;P command.
10. Breakpoint 2 is encountered again. DELTA displays the breakpoint message, and the instruction. The function is executed with the O command and the function output is displayed. The next instruction where the function returns control is displayed. Program execution continues with the ;P command.
11. Breakpoint 2 is encountered again. The instruction at offset 84 (in print_line) is displayed using !. This instruction is part of the setup for the call to the printf function.
12. Successive address locations are displayed by pressing the Linefeed key two times. These instructions are the remainder of the setup and the call to printf.
13. A breakpoint at X1+8C (the current address) is set using the ;B command. This breakpoint is in the function print_line. The . symbol represents the current address. Note that breakpoint 1 was cleared earlier and is now reused by DELTA for the new breakpoint.
14. Program execution continues with the ;P command.
15. Program execution stops at the new breakpoint 1, which is in the print_line function. DELTA displays the breakpoint message and the instruction at the new breakpoint. The O command halts program execution at the instruction where the function returns control, stepping over the routine call. Note the O command must be used in this case, as opposed to the ;P command, because the printf function resides in read-only protected memory. Program execution is continued with the ;P command.
16. Program execution stops at breakpoint 1 in the print_line function. Program execution is continued using a combination of the O and ;P commands.

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