OpenVMS Delta/XDelta Debugger Manual

Document revision date: 30 March 2001

OpenVMS Delta/XDelta Debugger Manual

Contents

Index

402,4F0/

This command changes the current address (. symbol) to the contents of the opened location. A subsequent Close Location command does not change the current address. However, a subsequent Close Current Location and Open Next command (ESC or LINEFEED) executes as follows:

Writes any new-exp specified
Closes the location opened by the / command
Adds the number of bytes (defined by the prevailing display width mode) to the address just opened with the / command
Changes the current address to the new value
Opens the new location and displays the contents

The display mode remains hexadecimal until the next Open Location and Display Contents in Instruction Mode (!) command or Open Location and Display Contents in ASCII Mode (") command.

In DELTA, not XDELTA, processes having the CMKRNL privilege can examine the address space of any existing process. Use pid to specify the internal PID of the process you want to examine. For example, use the following command to view address location 402 in the process with a PID of 00010010:

00010010:402/

On Alpha, DELTA also permits the examination of general purpose registers in another process. The PID specifies the internal PID of the process you want to examine. For example, use the following command to examine R5 in the process with a PID of 00010010:

00010010:R5/

Example

R0,R9/00000001 R1/00000000 R2/00000226 R3/7FF2AD94 R4/000019B4 R5/00000000 R6/7FF2AA49 R7/8001E4DD R8/7FFED052 R9/7FFED25A
Contents of all the general registers R0 through R9 are displayed.

! (Open Location and Display Contents in Instruction Mode)

Displays an instruction and its operands.

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 instruction, or the first address of the range of instructions, to display. If you do not specify this parameter, the address displayed is that currently specified by Q (last quantity displayed). When you want to view just one location, the syntax is as follows:

start-addr-exp!

end-addr-exp
The address of the last instruction in the range to display. When you want to view several instructions, the syntax is as follows:

start-addr-exp,end-addr-exp!

Each location within the range is displayed with the address, a slash (/), and the MACRO instruction.

Description

The Open Location and Display Contents in Instruction Mode command displays the contents of a location or range of locations as a MACRO instruction. DELTA/XDELTA does not make any distinction between reasonable and unreasonable instructions or instruction streams.
This command does not allow you to modify the contents of the location. The command sets a flag that causes subsequent Close Current Location and Display Next (LINEFEED) and Open Location and Display Indirect Location (TAB) commands to display MACRO instructions. You can clear the flag by using the Open Location and Display Contents (/) command, which displays the contents of the location as a hexadecimal number, or Open Location and Display Contents in ASCII Mode ("), which displays the contents of the location in ASCII.
When an address appears as an instruction's operand, DELTA/XDELTA sets the Q symbol to that address. Then enter ! again to go to the address specified in the instruction operand. DELTA/XDELTA changes Q only for operands that use program-counter or branch-displacement addressing modes; Q is not altered for operands that use literal and register addressing modes. This feature is useful for branches that follow.

Example

The following example applies only to OpenVMS VAX.
69B!BRB 0000067A (1) !CLRQ -(SP) (2)
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.
The instruction at address 67A is displayed using the ! command. The value of Q is used as the address location.

Example

The following example applies only to OpenVMS Alpha.
30000! LDA SP,#XFFE0(SP) (1) 00030004! BIS R31,R31,R18 (2)
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.
After typing a LINEFEED command, DELTA/XDELTA displays the next instruction location and the instruction at that address.

LINEFEED (Close Current Location, Open Next)

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 MACRO instructions, a series of register values, or a series of values on the stack.
The values in the symbol Q and the symbol . are changed automatically.

Example

The following example applies only to OpenVMS VAX.
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
Instruction at address 6B9 is displayed using the ! command.
Five successive instructions are displayed by pressing the Linefeed key five times. The LINEFEED command is not echoed on the terminal.

Example

The following example applies only to OpenVMS Alpha.
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
Instruction at address 30000 is displayed using the ! command.
Five successive instructions are displayed by pressing the Linefeed key five times. The LINEFEED command is not echoed on the terminal.

ESC (Open Location and Display Previous Location)

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

TAB (Open Location and Display Indirect Location)

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.

Example

The following example applies only to OpenVMS VAX.
69B!BRB 0000067A (1) [Tab] 0000067A/CLRQ -(SP) (2)
The instruction at 69B is displayed using the ! command. DELTA/XDELTA displays a branch instruction.
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.

Example

The following example applies only to OpenVMS Alpha.
10000/00083089 (1) 00010004/00000000 (2) 00010008/00030000 (3) 00030000/23DEFFE0
The contents of location 10000 are displayed using the / command.
The subsequent two locations are displayed using the LINEFEED command.
After displaying the contents of location 10008 (30000), the TAB command is used to display the contents of location 30000.

" (Open Location and Display Contents in ASCII)

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
The current display mode is word (displays one word in hexadecimal).
The " command changes the prevailing display mode to ASCII but does not affect the width of the display.
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.

RETURN (Close Current Location)

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

;Q
;C
;W
;I
;H
\string\

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

;B (Breakpoint)

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, 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, the format of the display differs slightly, as shown in the following example:
Brk n at address address!decoded-instruction
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, the CPU ID is displayed as a decimal number with no leading zeros.
On Alpha and VAX, 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 Alpha and VAX, 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)

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