HP OpenVMS Systems Documentation

HP OpenVMS Delta/XDelta Debugger Manual

1. The instruction at address 69B is displayed using the ! command. DELTA/XDELTA displays a branch instruction and sets Q (last address location displayed) to the branch address 67A.
2. The instruction at address 67A is displayed using the ! command. The value of Q is used as the address location.

Alpha example:

30000!       LDA         SP,#XFFE0(SP) (1)
00030004!     BIS         R31,R31,R18 (2)

1. The instruction at address 30000 is displayed using the ! command. DELTA/XDELTA displays a LDA instruction. Note that unlike on a VAX computer, an absolute address never appears in an instruction operand. So the value of Q has no use after an instruction display.
2. After typing a LINEFEED command, DELTA/XDELTA displays the next instruction location and the instruction at that address.

I64 example:

G0BF5D60!       add         r33 = 0008, r33 ;;      (1)
80BF5D62!       nop.i       000000 ;;        (2)
80BF5D70!       ld4         r2 = [r2] ;;
80BF5D71!       nop.m       000000
80BF5D72!       sxt4        r2 = r2 ;;
80BF5D80!       cmp.eq      p14, p0 = r2, r0
80BF5D81!       nop.f       000000
80BF5D82! (p14) br.cond.dpnt.few.clr 0000030 ;;
80BF5D90!       ld8         r14 = [r2], 008 ;;
80BF5D91!       nop.m       000000
80BF5D92!       mov         b7 = r14 ;;
80BF5DA0!       ld8         r1 = [r2]

1. The instruction at the base address G0BF5D60 is displayed using the ! command. XDELTA displays an add instruction.
2. After typing a LINEFEED command, XDELTA displays the next instruction location and the instruction at that address, and so on.

Displays the contents of a location as an ASCII string.

Format

[pid:] start-addr-exp[,end-addr-exp] "

Arguments

pid

The internal process identification (PID) of a process you want to access. If you specify zero, or do not specify any PID, the default process is the current process. This argument cannot be used with XDELTA.

Subsequent open location and display contents commands issued after using the pid argument, display the contents of the location of the specified process until you specify another PID with this command.

You can obtain the internal PID of processes by running the System Dump Analyzer utility (SDA). Use the SDA command SHOW SUMMARY to determine the external PID. Then use the SDA command SHOW PROCESS/INDEX to determine the internal PID. Refer to your operating system's System Dump Analyzer Utility Manual for more information about SDA commands.

start-addr-exp

The address of the location, or the start of a range of locations, to be displayed. If you want to view one location, the syntax is as follows:

start-add-exp"

end-addr-exp

The last address within a range of locations to be viewed. If you want to view a series of locations, the syntax is as follows:

start-add-exp,end-addr-exp"

Description

The Open Location and Display Contents in ASCII command opens the location or range of locations at start-addr-exp and displays the contents in ASCII format. This command does not change the width of the display (byte, word, longword) from the prevailing mode. If the prevailing mode is word mode, two ASCII characters are displayed; if byte mode, one character is displayed.

The display mode remains ASCII until you enter the next Open Location and Display Contents command (/) or Open Location and Display Contents in Instruction Mode command (!). These commands change the display mode to hexadecimal or instruction, respectively.

You can modify the contents of the locations, starting at start-addr-exp, with the Deposit ASCII string (') command.

Example

235FC2 [W/415A (1) 235FC2" ZA (2) [Linefeed] (3) 235FC4/PP

1. The current display mode is word (displays one word in hexadecimal).
2. The " command changes the prevailing display mode to ASCII but does not affect the width of the display.
3. The next Close Current Location, Open Next command (LINEFEED), determines the address of the location to open by adding the width, in bytes, to the value contained in the symbol . (the current address). Then it opens the number of bytes equal to the width of the prevailing display mode, which in this example is two bytes.
   The ASCII representation of the contents of the location presents the bytes left to right, while the hexadecimal representation presents them right to left.

Opens the previous location and displays its contents.

Format

ESC

Description

The Open Location and Display Previous Location command decrements the location counter (.) by the width (in bytes) of the prevailing display mode, opens that many bytes, and displays the contents on a new line. The address of the location is displayed on the new line in the prevailing mode, followed by a slash (/) and the contents of that address.

On VAX, this command is ignored if the prevailing display mode is instruction mode (set by the ! command).

On all platforms, use this command to move backwards through a series of locations. Set the address where you want to start (for example, with the / command). Then press the ESC key repeatedly to display each preceding location. ESC is echoed as a dollar sign ($) on the terminal.

On keyboards without a separate ESC key, press Ctrl/3 or the escape key sequence that you defined on your keyboard. The ESC key on LK201 keyboards (VT220, VT240, VT340, and workstation keyboards) generates different characters and cannot be used for the ESC command. You must use Ctrl/3.

Example

R1/00000000 (1) $ (2) [ESC] R0/00000001

1. The contents of general register 1 are displayed using the / command.
2. The contents of general register 0, the location prior to general register 1, are displayed by pressing ESC.

Terminates the DELTA debugging session. Use with DELTA only.

Format

EXIT

Description

Use the EXIT command to terminate a DELTA debugging session. You cannot use EXIT in XDELTA.

You may have to enter EXIT twice, such as when your program terminates execution by the $EXIT system service or by the Return key (to DCL).

Closes the currently open location and opens the next location, displaying its contents.

Format

LINEFEED

Description

The Close Current Location Open Next command closes the currently open location, then opens the next and displays its contents. This command accepts no arguments, and thus can only be used to open the next location. It is useful for examining a series of locations one after another. First, set the location where you want to start (for example, with the / or (!) command). Then, press the Linefeed key repeatedly to examine each successive location.

The LINEFEED command displays the contents of the next location in the prevailing display mode and display width. If the current display mode is hexadecimal (the / command was used) and the display width is word, the next location displayed is calculated by adding a word to the current location. Its contents are displayed in hexadecimal. If the current display mode is instruction, the next location displayed is the next instruction, and the contents are displayed as a MACRO instruction.

On keyboards without a separate Linefeed key, press CTRL/J. The Linefeed key on LK201 keyboards (VT220, VT240, VT340, and workstation keyboards) generates different characters and cannot be used for the LINEFEED command. You must use CTRL/J.

This command is useful for displaying a series of machine instructions, a series of register values, or a series of values on the stack or in memory.

The values in the symbol Q and the symbol . are changed automatically.

The following examples illustrate the command on each OpenVMS platform.

Examples

VAX example:

6B9!CLRQ -(SP) (1) [Linefeed] (2) 000006BB/CLRQ -(SP) [Linefeed] 000006BD/PUSHL X1+002E [Linefeed] 000006C1/PUSHAL X1+003A [Linefeed] 000006C5/CLRQ -(SP) [Linefeed] 000006C7/PUSHL #00

1. Instruction at address 6B9 is displayed using the ! command.
2. Five successive instructions are displayed by pressing the Linefeed key five times. The LINEFEED command is not echoed on the terminal.

Alpha example:

30000! LDA SP,#XFFE0(SP) (1) 00030004! BIS R31,R31,R18 (2) 00030008! STQ R27,(SP) 0003000C! BIS R31,R31,R19 00030010! STQ R26,#X0008(SP) 00030014! BIS R31,#X04,R25

1. Instruction at address 30000 is displayed using the ! command.
2. Five successive instructions are displayed by pressing the Linefeed key five times. The LINEFEED command is not echoed on the terminal.

I64 example:

G0BF5D60! add r33 = 0008, r33 ;; (1) 80BF5D62! nop.i 000000 ;; (2) 80BF5D71! nop.m 000000 80BF5D72! sxt4 r2 = r2 ;; 80BF5D80! cmp.eq p14, p0 = r2, r0 80BF5D81! nop.f 000000 80BF5D82! (p14) br.cond.dpnt.few.clr 0000030 ;; 80BF5D90! ld8 r14 = [r2], 008 ;; 80BF5D91! nop.m 000000 80BF5D92! mov b7 = r14 ;; 80BF5DA0! ld8 r1 = [r2]

1. The instruction at the base address G0BF5D60 is displayed using the ! command. XDELTA displays an add instruction.
2. Ten successive instructions are displayed by pressing the Linefeed key twelve times. The LINEFEED command is not echoed on the terminal.

Closes a location that has been opened by one of the open location and display contents commands.

Format

RETURN

Description

If you have opened a location with one of the open location and display contents commands (/, LINEFEED, ESC, TAB, !, or "), press the Return key to close the location. Use this command to make sure that a specific location has not been left open with the possibility of being overwritten.

You also press the Return key to terminate the following DELTA/XDELTA commands:

• ;X
• ;E
• ;G
• ;P
• ;B
• ;M
• 'string'
• ;L
• EXIT (DELTA only)

On Alpha and I64, the same is true for the commands that are specific to this implementation, as follow:

• ;Q
• ;C
• ;D
• ;H
• ;I
• ;T (I64 only)
• ;W
• \string\

On all platforms, you can also use the Return key as an ASCII character in a quoted string. Refer to the Deposit ASCII String command (').

Opens the location addressed by the contents of the current location and displays its contents.

Format

TAB

Description

The Open Location and Display Indirect Location command opens the location addressed by the contents of the current location and displays the contents of the addressed location on a new line. The display is in the prevailing display mode. This command is useful for examining data structures that have been placed in a queue, or the operands of instructions.

To execute this command, press the Tab key.

This command changes the current address (.) to the location displayed.

This command does not affect the display mode.

The following examples illustrate the command on each OpenVMS platform.

Examples

VAX example:

69B!BRB 0000067A (1) [Tab] 0000067A/CLRQ -(SP) (2)

1. The instruction at 69B is displayed using the ! command. DELTA/XDELTA displays a branch instruction.
2. The instruction at the address referred to by the branch instruction is displayed by pressing the Tab key. DELTA/XDELTA displays the instruction at address 67A.

VAX, Alpha, and I64 example:

10000/00083089 (1) 00010004/00000000 (2) 00010008/00030000 (3) 00030000/23DEFFE0

1. The contents of location 10000 are displayed using the / command.
2. The subsequent two locations are displayed using the LINEFEED command.
3. After displaying the contents of location 10008 (30000), the TAB command is used to display the contents of location 30000.

Shows, sets, and clears breakpoints.

Format

[addr-exp][,n][,display-addr-exp][,cmd-string-addr] ;B

Arguments

addr-exp

The address where you want the breakpoint.

n

The number to assign to the breakpoint. If you omit a number, DELTA/XDELTA assigns the first unused number to the breakpoint; if all numbers are in use, DELTA/XDELTA displays the error message, "Eh?".

On VAX, for XDELTA, the range is from 2 to 8. For XDELTA, breakpoint 1 is reserved for INI$BRK. For DELTA, the range is from 1 to 8.

On Alpha and I64, for XDELTA, the range is from 1 to 8. For DELTA, the range is from 1 to 8.

display-addr-exp

The address of a location, the contents of which are to be displayed in hexadecimal in the prevailing width mode when the breakpoint is encountered. Omit this argument by specifying zero or two consecutive commas. If omitted, DELTA/XDELTA displays only the instruction that begins at the specified address.

cmd-string-addr

The address of the string of DELTA/XDELTA commands to execute when this breakpoint is encountered. Refer to the Execute Command String (;E) command. DELTA/XDELTA displays the information requested before executing the string of commands associated with complex breakpoints. You must have previously deposited the string of commands using the ' command or have coded the string into an identifiable location in your program. If omitted, DELTA/XDELTA executes no commands automatically and waits for you to enter commands interactively.

Description

The breakpoint command shows, sets, and clears breakpoints. The action of this command depends on the arguments used with it. Each action is described below.

Displaying Breakpoints

To show all the breakpoints currently set, enter ;B. For each breakpoint, DELTA/XDELTA displays the following information:

• Number of the breakpoint
• Address of the breakpoint
• Address of a location the contents of which will be displayed when the breakpoint is encountered
• Address of the command string associated with this breakpoint (for complex breakpoints, refer to the section in this Description called Setting Complex Breakpoints)

Setting Simple Breakpoints

To set a breakpoint, enter an address expression followed by ;B. Then press the Return key, as follows:

addr-exp;B[Return]

DELTA/XDELTA sets a breakpoint at the specified location and assigns it the first available breakpoint number.

When DELTA/XDELTA reaches the breakpoint, it completes the following actions:

• Suspends instruction execution.
• Sets a flag to change the display mode to instruction mode. Any subsequent Close Current Location, Open Next (LINEFEED) commands, and Open and Display Indirect Location (TAB) commands will display locations as machine instructions.
• On VAX, the following message is displayed, listing the number of the breakpoint, the address of the breakpoint, and the instruction stored at the breakpoint location:

  n BRK at address address/decoded-instruction

  
  On Alpha and I64, the format of the display differs slightly, as shown in the following example:

  Brk n at address [on CPUn] [new mode =] [new IPL =] address!decoded-instruction

• On Alpha and I64 systems, if the interrupt priority level (IPL) has changed, the new IPL is printed (XDELTA only). Also on Alpha and I64 systems, if the processor mode has changed, the new mode is printed (both XDELTA and DELTA).

If you are using XDELTA in a multiprocessor environment, the CPU ID of the processor where the break was taken is also displayed.

On VAX, the CPU ID is displayed as a 2-digit hexadecimal number.

On Alpha and I64, the CPU ID is displayed as a decimal number with no leading zeros.

On all platforms, after the breakpoint message is displayed, you can enter other DELTA/XDELTA commands. You can reset the flag that controls the mode in which instructions are displayed by entering the Open Location and Display Contents (/) command.

Setting a Breakpoint and Assigning a Number to It

To set a breakpoint and assign it a number, enter the address where you want the breakpoint, a comma, a single digit for the breakpoint number, a semicolon (;), the letter B, and then press the Return key.

For example, if you wanted to set breakpoint 4 at address 408, the command is as follows:

408,4;B[Return]

DELTA/XDELTA sets a breakpoint at the specified location and assigns it the specified breakpoint number.

Clearing Breakpoints

To clear a breakpoint, enter zero (0), followed by a comma, the number of the breakpoint to remove, a semicolon (;), the letter B, and then press the Return key. DELTA/XDELTA clears the specified breakpoint. For example, if you wanted to clear breakpoint 4, the command is as follows:

0,4;B[Return]

On VAX, when using XDELTA, do not clear breakpoint 1. If you do, any calls to INI$BRK in your program will not result in entry into XDELTA.

Setting Complex Breakpoints

On all platforms, a complex breakpoint completes one or more of the following actions:

• Always displays the next instruction to be executed
• Optionally displays the contents of another, specified location
• Optionally executes a string of DELTA/XDELTA commands stored in memory

To use the complex breakpoint, you must first create the string of DELTA commands you want executed. Then deposit those commands at a memory location with the Deposit ASCII String command (').

To set a complex breakpoint, use the following syntax:

addr-exp,n,display-addr-exp,cmd-string-addr;B

Example

;B 1 00000690 2 00000699 (1) 0,2;B (2) ;B 1 00000690 (3) ;P (4)

1. Two breakpoints have already been set and are displayed. Using ;B, DELTA/XDELTA displays each breakpoint number and the address location of each breakpoint.
2. Breakpoint 2 is cleared.
3. Current breakpoints are displayed. Because breakpoint 2 has been cleared, DELTA/XDELTA displays just breakpoint 1.
4. Program execution is continued using the ;P command.

Displaying Breakpoints in a Multithreaded Application

To support the debugging of multithreaded applications, DELTA has the capability of displaying a thread ID at a breakpoint. When DELTA reaches a breakpoint in a multithreaded application, DELTA displays the thread ID and stops the execution of all other threads. (When DELTA reaches a breakpoint in a single-threaded application, the display and behavior is the same as in the past; DELTA displays the address and stops program execution.)

In the following example, a breakpoint is set in a multithreaded application with 30000;B and is followed by the ;P (Proceed from Breakpoint) command. The breakpoint is taken. Because it is a multithreaded application, the thread ID is included in the display.

30000;B  ;P
Brk 1 at 30000 on Thread 12
00030000!  LDA  SP,#XFF80(SP)