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OpenVMS Debugger Manual
SHOW STACK
Displays information on the currently active routine calls.
Format
SHOW STACK [integer]
Parameters
integer
Specifies the number of frames to display. If you omit the parameter,
the debugger displays information about all call frames.
Description
For each call frame, the SHOW STACK command displays information such
as the condition handler, saved register values, and the argument list,
if any. The latter is the list of arguments passed to the subroutine
with that call. In some cases the argument list can contain the
addresses of actual arguments. In such cases, use the EXAMINE
address-expression command to display the values of these
arguments.
On VAX processors, each routine invocation results in a call frame on
the call stack.
On Alpha processors, a routine invocation can result in a stack frame
procedure (with a call frame on the stack), a register frame procedure
(with a call frame stored in the register set), or a null frame
procedure (without a call frame). SHOW STACK provides information on
all three: stack frame procedures, register frame procedures, and null
frame procedures. (See Example 2 below.)
Related command:
SHOW CALLS
Examples
| #1 |
DBG> SHOW STACK
stack frame 0 (2146814812)
condition handler: 0
SPA: 0
S: 0
mask: ^M<R2>
PSW: 0000 (hexadecimal)
saved AP: 7
saved FP: 2146814852
saved PC: EIGHTQUEENS\%LINE 69
saved R2: 0
argument list:(1) EIGHTQUEENS\%LINE 68+2
stack frame 1 (2146814852)
condition handler: SHARE$PASRTL+888
SPA: 0
S: 0
mask: none saved
PSW: 0000 (hexadecimal)
saved AP: 2146814924
saved FP: 2146814904
saved PC: SHARE$DEBUG+667
DBG>
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In this example for VAX systems, the SHOW STACK command displays
information about all call stack frames at the current PC location.
| #2 |
DBG> SHOW STACK
invocation block 0
FP: 000000007F907AD0
Detected what appears to be a NULL frame
NULL frames operate in the same invocation context as their caller
NULL Procedure Descriptor (0000000000010050):
Flags: 3089
KIND: PDSC$K_KIND_FP_STACK (09)
Signature Offset 0000
Entry Address: MAIN\FFFF
Procedure Descriptor (0000000000010000):
Flags: 3089
KIND: PDSC$K_KIND_FP_STACK (09)
FP is Base Register
Rsa Offset: 0008
Signature Offset 0000
Entry Address: MAIN
Ireg Mask: 20000004 <R2,FP>
RA Saved @ 000000007F907AD8: FFFFFFFF8255A1F8
R2 Saved @ 000000007F907AE0: 000000007FFBF880
FP Saved @ 000000007F907AE8: 000000007F907B30
Freg Mask: 00000000
Size: 00000020
invocation block 1
FP: 000000007F907B30
Procedure Descriptor (FFFFFFFF8255D910):
Flags: 3099
KIND: PDSC$K_KIND_FP_STACK (09)
Handler Valid
FP is Base Register
Rsa Offset: 0048
Signature Offset 0001
Entry Address: -2108317536
Ireg Mask: 20002084 <R2,R7,R13,FP>
RA Saved @ 000000007F907B78: 000000007FA28160
R2 Saved @ 000000007F907B80: 0000000000000000
R7 Saved @ 000000007F907B88: 000000007FF9C9E0
R13 Saved @ 000000007F907B90: 000000007FA00900
FP Saved @ 000000007F907B98: 000000007F907BB0
Freg Mask: 00000000
Size: 00000070
Condition Handler: -2108303104
DBG>
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This example is for Alpha systems. Note that sections of routine
prologues and epilogues appear to the debugger to be
null frames. The portion of the prologue before the change in the frame
pointer (FP) and the portion of the epilogue after restoration of the
FP each look like a null frame, and are reported accordingly.
SHOW STEP
Identifies the default qualifiers (/INTO, /INSTRUCTION, /NOSILENT and
so on) currently in effect for the STEP command.
Format
SHOW STEP
Description
The default qualifiers for the STEP command are the default qualifiers
last established by the SET STEP command. If you did not enter a SET
STEP command, the default qualifiers are /LINE, /OVER, /NOSILENT, and
/SOURCE.
Enabling screen mode by pressing PF1-PF3 enters the SET STEP NOSOURCE
command as well as the SET MODE SCREEN command (to eliminate redundant
source display in output and DO displays). In that case, the default
qualifiers are /LINE, /OVER, /NOSILENT, and /NOSOURCE.
Related commands:
STEP
SET STEP
Example
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DBG> SET STEP INTO,NOSYSTEM,NOSHARE,INSTRUCTION,NOSOURCE
DBG> SHOW STEP
step type: nosystem, noshare, nosource, nosilent, into routine calls,
by instruction
DBG>
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In this example, the SHOW STEP command indicates that the debugger take
the following actions:
- Steps into called routines, but not those in system space or in
shareable images
- Steps by instruction
- Does not display lines of source code while stepping
SHOW SYMBOL
Displays information about the symbols in the debugger's run-time
symbol table (RST) for the current image.
Note
The current image is either the main image (by default) or the image
established as the current image by a previous SET IMAGE command.
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Format
SHOW SYMBOL symbol-name[,...] [IN scope[,...]]
Parameters
symbol-name
Specifies a symbol to be identified. A valid symbol name is a single
identifier or a label name of the form %LABEL n, where
n is an integer. Compound names such as RECORD.FIELD or
ARRAY[1,2] are not valid. If you specify the asterisk (*) wildcard
character by itself, all symbols are listed. You can use the wildcard
within a symbol name.
scope
Specifies the name of a module, routine, or lexical block, or a numeric
scope. It has the same syntax as the scope specification in a SET SCOPE
command and can include path-name qualification. All specified scopes
must be in set modules in the current image.
The SHOW SYMBOL command displays only those symbols in the RST for the
current image that both match the specified name and are declared
within the lexical entity specified by the scope
parameter. If you omit this parameter, all set modules and the global
symbol table (GST) for the current image are searched for symbols that
match the name specified by the symbol-name parameter.
Qualifiers
/ADDRESS
Displays the address specification for each selected symbol. The
address specification is the method of computing the symbol's address.
It can merely be the symbol's memory address, but it can also involve
indirection or an offset from a register value. Some symbols have
address specifications too complicated to present in any understandable
way. These address specifications are labeled "complex address
specifications."
On Alpha processors, the command SHOW SYMBOL/ADDRESS
procedure-name displays both the code address and
procedure descriptor address of a specified routine, entry point, or
Ada package.
/DEFINED
Displays symbols you have defined with the DEFINE command (symbol
definitions that are in the DEFINE symbol table).
/DIRECT
Displays only those symbols that are declared directly in the
scope parameter. Symbols declared in lexical entities
nested within the scope specified by the scope parameters are not shown.
/FULL
Displays all information associated with the /ADDRESS, /TYPE, and
/USE_CLAUSE qualifiers.
For C++ modules, if symbol-name is a class, SHOW
SYMBOL/FULL also displays information about the class.
/LOCAL
Displays symbols that are defined with the DEFINE/LOCAL command (symbol
definitions that are in the DEFINE symbol table).
/TYPE
Displays data type information for each selected symbol.
/USE_CLAUSE
(Applies to Ada programs.) Identifies any Ada package that a specified
block, subprogram, or package names in a use clause. If the symbol
specified is a package, also identifies any block, subprogram, package,
and so on, that names the specified symbol in a use clause.
Description
The SHOW SYMBOL command displays information that the debugger has
about a given symbol in the current image. This information might not
be the same as what the compiler had or even what you see in your
source code. Nonetheless, it is useful for understanding why the
debugger might act as it does when handling symbols.
If you do not specify a qualifier, the SHOW SYMBOL command lists all of
the possible declarations or definitions of a specified symbol that
exist in the RST for the current image (that is, in all set modules and
in the GST for that image). Symbols are displayed with their path
names. A path name identifies the search scope (module, nested
routines, blocks, and so on) that the debugger must follow to reach a
particular declaration of a symbol. When specifying symbolic address
expressions in debugger commands, use path names only if a symbol is
defined multiple times and the debugger cannot resolve the ambiguity.
The /DEFINED and /LOCAL qualifiers display information about symbols
defined with the DEFINE command (not the symbols that are derived from
your program). The other qualifiers display information about symbols
defined within your program.
For information specific to Ada programs, type Help Language_Support
Ada.
Related commands:
DEFINE
DELETE
SET MODE [NO]LINE
SET MODE [NO]SYMBOLIC
SHOW DEFINE
SYMBOLIZE
Examples
| #1 |
DBG> SHOW SYMBOL I
data FORARRAY\I
DBG>
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This command shows that symbol I is defined in module FORARRAY and is a
variable (data) rather than a routine.
| #2 |
DBG> SHOW SYMBOL/ADDRESS INTARRAY1
data FORARRAY\INTARRAY1
descriptor address: 0009DE8B
DBG>
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This command shows that symbol INTARRAY1 is defined in module FORARRAY
and has a memory address of 0009DE8B.
This command lists all the symbols whose names contain the string
"PL".
| #4 |
DBG> SHOW SYMBOL/TYPE COLOR
data SCALARS\MAIN\COLOR
enumeration type (primary, 3 elements), size: 4 bytes
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This command shows that the variable COLOR is an enumeration type.
| #5 |
DBG> SHOW SYMBOL/TYPE/ADDRESS *
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This command displays all information about all symbols.
| #6 |
DBG> SHOW SYMBOL * IN MOD3\COUNTER
routine MOD3\COUNTER
data MOD3\COUNTER\X
data MOD3\COUNTER\Y
DBG>
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This command lists all the symbols that are defined in the scope
denoted by the path name MOD3\COUNTER.
| #7 |
DBG> DEFINE/COMMAND SB=SET BREAK
DBG> SHOW SYMBOL/DEFINED SB
defined SB
bound to: SET BREAK
was defined /command
DBG>
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In this example, the DEFINE/COMMAND command defines SB as a symbol for
the SET BREAK command. The SHOW SYMBOL/DEFINED command displays that
definition.
SHOW TASK|THREAD
Displays information about the tasks of a multithread program (also
called a tasking program).
Format
SHOW THREAD [task-spec[,...]]
Parameters
task-spec
Specifies a task value. Use any of the following forms:
- When the event facility is THREADS:
- A task (thread) name as declared in the program, or a language
expression that yields a task ID number.
- A task ID number (for example, 2), as indicated in a SHOW THREAD
display.
- When the event facility is ADA:
- A task (thread) name as declared in the program, or a language
expression that yields a task value. You can use a path name.
- A task ID (for example, 2), as indicated in a SHOW THREAD display.
- One of the following task built-in symbols:
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%ACTIVE_TASK
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The task that runs when a GO, STEP, CALL, or EXIT command executes.
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%CALLER_TASK
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(Applies only to Ada programs.) When an accept statement executes, the
task that called the entry associated with the accept statement.
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%NEXT_TASK
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The task after the visible task in the debugger's task list. The
ordering of tasks is arbitrary but consistent within a single run of a
program.
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%PREVIOUS_TASK
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The task previous to the visible task in the debugger's task list.
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%VISIBLE_TASK
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The task whose call stack and register set are the current context for
looking up symbols, register values, routine calls, breakpoints, and so
on.
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Do not use the asterisk (*) wildcard character. Instead, use the /ALL
qualifier. Do not specify a task with /ALL, /STATISTICS, or /TIME_SLICE.
Qualifiers
/ALL
Selects all existing tasks for display---namely, tasks that have been
created and (in the case of Ada tasks) whose master has not yet
terminated.
/CALLS[=n]
Does a SHOW CALLS command for each task selected for display. This
identifies the currently active routine calls (the call stack) for a
task.
/FULL
When the event facility is THREADS, use the PTHREAD thread -f
thread-number command.
Displays additional information for each task selected for display. The
additional information is provided if you use /FULL by itself or with
/CALLS or /STATISTICS.
/HOLD
/NOHOLD (default)
When the event facility is THREADS, use the PTHREAD tset -n
thread-number command.
Selects either tasks that are on hold, or tasks that are not on hold
for display.
If you do not specify a task, /HOLD selects all tasks that are on hold.
If you specify a task list, /HOLD selects the tasks in the task list
that are on hold.
If you do not specify a task, /NOHOLD selects all tasks that are not on
hold. If you specify a task list, /NOHOLD selects the tasks in the task
list that are not on hold.
/IMAGE
Displays the image name for each active call on the call stack. Valid
only with the /CALLS qualifier.
/PRIORITY=(n[,...])
When the event facility is THREADS, use the PTHREAD tset -s
thread-number command.
If you do not specify a task, selects all tasks having any of the
specified priorities, n, where n is a decimal integer
from 0 to 15. If you specify a task list, selects the tasks in the task
list that have any of the priorities specified.
/STATE=(state[,...])
If you do not specify a task, selects all tasks that are in any of the
specified states---RUNNING, READY, SUSPENDED, or TERMINATED. If you
specify a task list, selects the tasks in the task list that are in any
of the states specified.
/STATISTICS
(Compaq Ada on VAX only) Displays task statistics for the entire
tasking system. This information enables you to measure the performance
of your tasking program. The larger the number of total schedulings
(also known as context switches), the more tasking overhead there is.
/TIME_SLICE
(VAX only) Displays the current time-slice value, in seconds, as
specified by a previous SET TASK/TIME_SLICE command. If no SET
TASK/TIME_SLICE command was previously entered, displays the time-slice
value, if any, that was specified in the program. If no time-slice
value was previously established, the value is 0.0---that is, time
slicing is disabled.
/TIME_SLICE is valid only when the event facility is ADA.
Description
Note
SHOW TASK and SHOW THREAD are synonymous commands. They perform
identically.
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A task can first appear in a SHOW THREAD display as soon as it is
created. A task can no longer appear in a SHOW THREAD display if it is
terminated or (in the case of an Ada tasking program) if its master is
terminated. By default, the SHOW THREAD command displays one line of
information for each task selected.
When you specify the /IMAGE qualifier, the debugger first does a SET
IMAGE command for each image that has debug information (that is, it
was linked using the /DEBUG or /TRACEBACK qualifier). The debugger then
displays the image name for each active call on the calls stack. The
output display has been expanded and displays the image name in the
first column.
The debugger suppresses the share$image_name module name, because that
information is provided by the /IMAGE qualifier.
The SET IMAGE command lasts only for the duration of the SHOW
THREAD/CALLS/IMAGE command. The debugger restores the set image state
when the SHOW THREAD/CALLS/IMAGE command is complete.
Related commands:
DEPOSIT/TASK
EXAMINE/TASK
(SET, SHOW) EVENT_FACILITY
SET TASK|THREAD
Examples
| #1 |
DBG> SHOW EVENT_FACILITY
event facility is ADA
...
DBG> SHOW TASK/ALL
task id pri hold state substate task object
* %TASK 1 7 RUN 122624
%TASK 2 7 HOLD SUSP Accept H4.MONITOR
%TASK 3 6 READY Entry call H4.CHECK_IN
DBG>
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In this example, the SHOW EVENT_FACILITY command identifies ADA as the
current event facility. The SHOW TASK/ALL command provides basic
information about all the tasks that were created through Ada services
and currently exist. One line is devoted to each task. The active task
is marked with an asterisk (*). In this example, it is also the active
task (the task that is in the RUN state).
| #2 |
DBG> SHOW TASK %ACTIVE_TASK,3,MONITOR
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This command selects the active task, 3, and task MONITOR for display.
| #3 |
DBG> SHOW TASK/PRIORITY=6
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This command selects all tasks with priority 6 for display.
| #4 |
DBG> SHOW TASK/STATE=(RUN,SUSP)
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This command selects all tasks that are either running or suspended for
display.
| #5 |
DBG> SHOW TASK/STATE=SUSP/NOHOLD
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This command selects all tasks that are both suspended and not on hold
for display.
| #6 |
DBG> SHOW TASK/STATE=(RUN,SUSP)/PRIO=7 %VISIBLE_TASK, 3
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This command selects for display those tasks among the visible task and
%TASK 3 that are in either the RUNNING or SUSPENDED state and have
priority 7.
SHOW TERMINAL
Identifies the current terminal screen height (page) and width being
used to format output.
Note
This command is not available in the Compaq DECwindows Motif for OpenVMS user interface to
the debugger.
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Format
SHOW TERMINAL
Description
The current terminal screen height and width are the height and width
last established by the SET TERMINAL command. By default, if you did
not enter a SET TERMINAL command, the current height and width are the
height and width known to the terminal driver, as displayed by the DCL
command SHOW TERMINAL (usually 24 lines and 80 columns for VT-series
terminals).
Related commands:
SET TERMINAL
SHOW DISPLAY
SHOW WINDOW
Example
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DBG> SHOW TERMINAL
terminal width: 80
page: 24
wrap: 80
DBG>
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This command displays the current terminal screen width and height
(page) as 80 columns and 24 lines, and the message wrap setting at
column 80.
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