HP OpenVMS Systems Documentation
OpenVMS Debugger Manual
7.9 Saving Displays and the Screen State
The SAVE command enables you to make a snapshot of an existing display and save that copy as a new display. This is useful if, for example, you later want to refer to the current contents of an automatically updated display (such as a DO display).
In the following example, the SAVE command saves the current contents of display CALLS into display CALLS4, which is created by the command:
The new display is removed from the pasteboard. To view its contents, use the DISPLAY command:
The EXTRACT command has two uses. First, it enables you to save the contents of a display in a text file. For example, the following command extracts the contents of display CALLS, appending the resulting text to the file COB34.TXT:
Second, the EXTRACT/SCREEN_LAYOUT command enables you to create a command procedure that can later be executed during a debugging session to re-create the previous state of the screen. In the following example, the EXTRACT/SCREEN_LAYOUT command creates a command procedure with the default specification SYS$DISK:DBGSCREEN.COM. The file contains all the commands needed to re-create the current state of the screen.
Note that you cannot save the PROMPT display as another display, or
extract it into a file.
During a debugging session, you can change the height or width of your terminal screen. One reason might be to accommodate long lines that would wrap if displayed across 80 columns. Or, if you are at a workstation, you might want to reformat your debugger window relative to other windows.
To change the screen height or width, use the SET TERMINAL command. The general effect of the command is the same whether you are at a VT-series terminal or at a workstation.
In this example, assume you are using a workstation window in its default emulated VT100-screen mode, with a screen size of 24 lines by 80 columns. You have started the debugger and are using it in screen mode. You now want to take advantage of the larger screen. The following command increases the screen height and width of the debugger window to 35 lines and 110 columns respectively:
By default, all displays are dynamic. A dynamic display automatically adjusts its window dimensions in proportion when a SET TERMINAL command changes the screen height or width. This means that, when using the SET TERMINAL command, you preserve the relative positions of your displays. The /[NO]DYNAMIC qualifier on the DISPLAY command lets you control whether or not a display is dynamic. If a display is not dynamic, it does not change its window coordinates after you enter a SET TERMINAL command (you can then use the DISPLAY, MOVE, or EXPAND commands, or various keypad key combinations, to move or resize a display).
Note that the debugger's SET TERMINAL command does not affect the
terminal screen size at DCL level. When you exit the debugger, the
original screen size is maintained.
The following built-in symbols are available for specifying displays and screen parameters in language expressions:
7.11.1 Screen Height and Width
The built-in symbols %PAGE and %WIDTH return, respectively, the current height and width of the terminal screen. These symbols can be used in various expressions, such as for window specifications. For example, the following command defines a window named MIDDLE that occupies a region around the middle of the screen:
7.11.2 Display Built-In Symbols
Each time you refer to a specific display with a DISPLAY command, the display list is updated and reordered, if necessary. The most recently referenced display is put at the tail of the display list, because that display is pasted last on the pasteboard (you can identify the display list by entering a SHOW DISPLAY command).
You can use display built-in symbols to specify displays relative to their positions in the display list. These symbols, listed as follows, enable you to refer to displays by their relative positions in the list instead of by their explicit names. The symbols are used mainly in keypad key definitions or command procedures.
Display symbols treat the display list as a circular list. Therefore, you can enter commands that use display symbols to cycle through the display list until you reach the display you want.
7.12 Screen Dimensions and Predefined Windows
On a VT-series terminal, the screen consists of 24 lines by 80 or 132 columns. On a workstation, the screen is larger in both height and width. The debugger can accommodate screen sizes up to 100 lines by 255 columns.
The debugger has many predefined windows that you can use to position displays on the screen. In addition to the full height and width of the screen, the predefined windows include all possible regions that result from:
The SHOW WINDOW command identifies all predefined display windows.
The following conventions apply to the names of predefined windows. The prefixes L and R denote left and right windows, respectively. Other letters denote the full screen (FS) or fractions of the screen height (H: half, T: third, Q: quarter, S: sixth, E: eighth). The trailing numbers denote specific segments of the screen height, starting from the top. For example:
The following four commands create displays that have windows identical in size and location (the top half of the screen):
The horizontal boundaries (start-column, column-count) of the predefined windows for the default terminal screen width of 80 columns are as follows:
Table 7-2 lists the vertical boundaries (start-line, line-count) of single-segment display windows predefined for the default terminal screen height of 24 lines. Table 7-2 does not list windows that consist of multiple segments such as E23 (a display window created from the combination of display windows E2 and E3).
7.13 Internationalization of Screen Mode
You can enable country-specific features for screen mode by defining logical names, as follows:
The Compaq DECwindows Motif for OpenVMS user interface to the OpenVMS Debugger Version 7.1 or later requires Version 1.2 or later of Compaq DECwindows Motif for OpenVMS.
This chapter provides the following information:
For information about starting a debugging session, see Chapter 9.
For detailed information about using the Motif interface for debugging,
see Chapter 10. For the source code of program EIGHTQUEENS.EXE,
shown in the figures of this chapter, see Appendix D.
The OpenVMS Debugger has a Compaq DECwindows Motif for OpenVMS graphical user interface (GUI) for workstations. This enhancement to the screen-mode command interface accepts mouse input to choose items from menus and to activate or deactivate push buttons, to drag the pointer to select text in windows, and so on. The debugger's Compaq DECwindows Motif for OpenVMS GUI menus and push buttons provide the functions for most basic debugging tasks.
The Compaq DECwindows Motif for OpenVMS GUI is layered on the character-cell command interface and has a command-entry prompt on the command line (in the command view). From the Compaq DECwindows Motif for OpenVMS GUI command line, you can enter debugger commands for the following purposes:
You can customize the Compaq DECwindows Motif for OpenVMS GUI to associate other debugger commands with new or existing push buttons.
You can run the Compaq DECwindows Motif for OpenVMS GUI in local mode or in client/server mode. Client/server mode allows you to debug programs remotely from another OpenVMS node. The user interface in both Motif modes is virtually identical. Chapter 9 describes how to start interfaces.
The Compaq DECwindows Motif for OpenVMS GUI does not recognize the HELP command at its command-entry prompt. Choose the On Commands item in the Help menu for online help on debugger commands.
You cannot use the Compaq DECwindows Motif for OpenVMS GUI to debug detached processes such as print symbionts that run without a command line interpreter (CLI). See Section 1.11 for details about debugging detached processes that do not have a CLI.
The following paragraphs highlight some of the convenience features of the debugger's default Compaq DECwindows Motif for OpenVMS interface. Section 8.2 gives visual details. (Convenience features of the debugger's command interface are described in detail in Section 1.1.2.)
The OpenVMS Debugger is a source-level debugger. The debugger displays in the source view the source code that surrounds the instruction where program execution is paused currently. You can enable and disable the display of compiler-generated line numbers.
A source browser lets you:
The call-stack menu on the main window lists the sequence of routine calls currently on the call stack. Click on a routine name in the call-stack menu to set (to that routine) the context (scope) for
You set, activate, and deactivate breakpoints by clicking on buttons next to the source lines in the source view or the instruction view. Optionally, you can set, deactivate, or activate breakpoints by selecting items in window pull-down menus, pop-up menus, context-sensitive menus, or dialog boxes. You can set conditional breakpoints, which suspend program execution if the specified condition is true. You can set action breakpoints, which execute one or more debugger commands when the breakpoint suspends program execution. The main window push buttons, the instruction view push buttons, and the breakpoint view give a visual indication of activated, deactivated, and conditional breakpoints.
Push buttons in the push button view control common operations: by clicking on a push button, you can start execution, step to the next source line, display the value of a variable selected in a window, interrupt execution, and so on.
You can modify, add, remove, and resequence push buttons and the associated debugger commands.
Context-sensitive pop-up menus list common operations associated with your view (source view, command view, and so on.) When you click MB3, the pop-up menu lists actions for the text you have selected, the source line at which you are pointing, or the view in which you are working.
To display the value of a variable or expression, select the variable or expression in the source view and click on a push button, such as EVAL (evaluate expression) or EX (examine variable). You can also display selected values by choosing items from window pull-down menus (such as Examine, in the Commands pull-down menu), context-sensitive menus, or dialog boxes. You can display values in different type or radix formats.
To change the value of a variable, edit the currently displayed value in the monitor view. You can also change values by selecting items in window pull-down menus (such as Deposit, in the Commands pull-down menu), context-sensitive pop-up menus, or dialog boxes.
The monitor view displays the updated values of specified variables whenever the debugger regains control from your program.
You can run the debugger in a state known as the kept debugger from which you can rerun the same program or run another program without exiting the debugger. When rerunning a program, you can choose to save the current state of breakpoints, tracepoints, and static watchpoints. The kept debugger is also available in the screen mode debugger. See Section 9.1 for information on starting the kept debugger.
You can run the debugger in a client/server configuration, which allows you to debug programs that run on an OpenVMS node remotely from another OpenVMS node using the Compaq DECwindows Motif for OpenVMS interface, or from a PC using the Microsoft Windows interface. Up to 31 debug clients can simultaneously access the same debug server, which allows many debugging options.
The instruction view shows the decoded instruction stream (the code that is actually executing) of your program. This view is useful if the program you are debugging has been optimized by the compiler, in which case the source code in the source view may not reflect the code that is executing. You can set breakpoints on instructions and display the memory addresses and source-code line numbers associated with each instruction.
The register view displays the current contents of all machine registers. You can edit the displayed values to deposit other values into the registers.
The debugger has a status indicator to identify the state of the debugger, which can be one of the following:
The tasking view displays information about the current state of all tasks of a tasking program (also called a multithread program). You can modify task characteristics to control task execution, priority, state transitions, and so on.
The debugger's Compaq DECwindows Motif for OpenVMS GUI is an enhancement to the character-cell debugger. It is layered on, and closely integrated with, the command-driven character-cell debugger:
You can edit program source code without exiting from the debugger. In the editor view, you can display the source code, search and replace text, or add additional text. Editor view text buffers allow you to move quickly back and forth between new or existing files, and copy, cut, and paste text from buffer to buffer.
The text editor available through the debugger's Compaq DECwindows Motif for OpenVMS menu interface is a simple convenience feature, not intended to replace sophisticated text editors such as the Language-Sensitive Editor (LSE). To use a different editor, enter the Edit command at the DBG> prompt in the command view (see the EDIT command).
You can modify the following and other aspects of the debugger's Compaq DECwindows Motif for OpenVMS interface and save the current settings in a resource file to customize your debugger startup environment: