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Updated: 11 December 1998

OpenVMS Debugger Manual


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C.15.4.1 Specifications

The following paragraphs describe where you can set breakpoints (or tracepoints) in specifications, using line numbers.

The RPG II program cycle determines the order in which program lines are processed. When setting breakpoints or tracepoints, you can reference the line numbers that RPG II assigns to your program and appear in a listing file or in a debugger source display. The line numbers you specify in columns 1 through 5 of a specification are not used.

The compiler assigns line numbers only to certain specifications at specific points in the logic cycle; therefore, you can specify a breakpoint or tracepoint at these points in the program:

C.15.4.2 Labels

You can specify an RPG II label as a breakpoint or a tracepoint. The following RPG II labels, which correspond to specific points in the logic cycle, are provided in addition to user-defined tags. Note that these labels do not appear in the source code but are accessible from the debugger. The labels do appear in the machine code listing.
RPG II Label Description and Breakpoint Behavior
*DETL Breaks just before outputting heading and detail lines
*GETIN Breaks just before reading the next record from the primary or secondary file
*TOTC Breaks just before performing total-time calculations
*TOTL Breaks just before performing total-time output
*OFL Breaks just before performing overflow output
*DETC Breaks just before performing detail-time calculations

For example:


DBG> SET BREAK *TOTL

C.15.5 EXAMINE Command

The EXAMINE command enables you to look at the contents of a variable, the current table entry, an array element, or the I/O buffer.

C.15.6 DEPOSIT Command

Note the following points when using the DEPOSIT command:

C.15.7 EDIT Command

The EDIT command invokes the RPG II editor rather than the DEC Language-Sensitive Editor.

C.16 SCAN (VAX Only)

The following subtopics describe debugger support for SCAN.

C.16.1 Operators in Language Expressions

Supported SCAN operators in language expressions include:
Kind Symbol Function
Prefix + Unary plus
Prefix - Unary minus (negation)
Infix + Addition
Infix - Subtraction
Infix * Multiplication
Infix / Division
Infix & Concatenation
Infix = Equal to
Infix <> Not equal to
Infix > Greater than
Infix >= Greater than or equal to
Infix < Less than
Infix <= Less than or equal to
Prefix NOT Complement
Infix AND Intersection
Infix OR Union
Infix XOR Exclusive OR

C.16.2 Constructs in Language and Address Expressions

Supported constructs in language and address expressions for SCAN follow:
Symbol Construct
( ) Subscripting
. (period) Record component selection
-> Pointer dereferencing

C.16.3 Predefined Symbols

Supported SCAN predefined symbols follow:
Symbol Meaning
TRUE Boolean True
FALSE Boolean False
NIL Nil pointer

C.16.4 Data Types

Supported SCAN data types follow:
SCAN Data Type Operating System Data Type Name
BOOLEAN (None)
INTEGER Longword Integer (L)
POINTER (None)
FIXED STRING ( n) TEXT with CLASS=S
VARYING STRING ( n) TEXT with CLASS=VS
DYNAMIC STRING TEXT with CLASS=D
TREE (None)
TREEPTR (None)
RECORD (None)
OVERLAY (None)

There is no specific support for the following data types:

C.16.5 Names

You can use the names of the following SCAN constructs in debugger commands:

C.16.6 Controlling Execution

Note the following points about SCAN breakpoints, tracepoints, and watchpoints.

C.16.6.1 Breakpoints and Tracepoints

You can set breakpoints and tracepoints on procedures, trigger macros, syntax macros, and labels, as well as line numbers. For example:


DBG> SET BREAK find_keyword    ! break on a trigger macro
DBG> CANCEL BREAK exit         ! cancel break on label
DBG> SET BREAK compare_trees   ! break on a procedure

Conventional breakpoints and tracepoints are not especially convenient for monitoring SCAN's picture matching. Where do you set a breakpoint or tracepoint to observe the tokens built by your program? There is no statement in your program on which to set such a breakpoint.

To solve this problem, VAX SCAN defines several events. By setting breakpoints or tracepoints on these events, you can observe the picture matching process.

The following event keywords are defined for SCAN programs:
Event Keyword Description
TOKEN A token is built.
PICTURE An operand in a picture is being matched.
INPUT A new line of the input stream is read.
OUTPUT A new line of the output stream is written.
TRIGGER A trigger macro is starting or terminating.
SYNTAX A syntax macro is starting or terminating.
ERROR Picture matching error recovery is starting or terminating.

Use these keywords with the /EVENT qualifier of the following commands:

For example, the following command sets a breakpoint that triggers whenever a TOKEN is built:


DBG> SET BREAK/EVENT=TOKEN

Recognition of SCAN events is enabled automatically by the debugger if the main program is written in SCAN. If you are debugging a program written in another language that calls a SCAN routine, proceed as follows to set up the SCAN environment:

  1. Enter the SET LANGUAGE SCAN command to enable recognition of language-dependent operators, expressions, and other constructs (see the SET LANGUAGE command).
  2. Enter the SET EVENT_FACILITY SCAN command to enable recognition of SCAN events (see the SET EVENT_FACILITY command). The SHOW EVENT_FACILITY command identifies the current facility and its events.

C.16.6.2 Watchpoints

Note the following points about SCAN watchpoints:

C.16.7 Examining and Depositing

The following subtopics explain how to examine and deposit into the following SCAN variables:

C.16.7.1 STRING Variables

If you deposit into a FIXED STRING variable, truncation will occur if the deposited string is longer than the size established by the declaration of that variable.

If you deposit into a VARYING STRING variable, truncation will occur if the deposited string is longer than the maximum size established by the declaration of that variable.

If you deposit into a DYNAMIC STRING variable, truncation will occur if the deposited string is longer than the current size of the variable.

With FIXED and DYNAMIC STRING variables, if the deposited string is shorter than the current size of the variable, the unfilled portion of the variable will be blank padded to the right, with the new string left justified in the variable.

In the case of VARYING STRING variables, the current size of the variable storage space will be adjusted to the size of the deposited string.

C.16.7.2 FILL Variables

Examining a FILL variable causes the contents of the specified variable to be displayed as a string, by default, and so may have little meaning. If the characteristics (or type) of the fill are known, the appropriate qualifier applied to the command will produce a more meaningful display. The following command example shows a fill x that is known to be a single floating number:


DBG> EXAMINE/FLOAT x

C.16.7.3 POINTER Variables

You can examine a POINTER by name to find the address of the variable it points to. Use the operator that combines the minus sign and the greater than symbol (->) to examine the variable that is based on the POINTER.

Consider these declarations and assignments:


TYPE symnode: RECORD 
                 ptr:  POINTER TO symnode, 
                 vstr: VARYING STRING( 20 ), 
              END RECORD; 
 
DECLARE x   : symnode; 
DECLARE xptr: POINTER TO symnode; 
xptr        = POINTER(x); 
x.vstr      = 'prehensile'; 

The following command displays the value of the vstr component of x:


DBG> EXAMINE x.vstr
POINTER\MAINPOINTER\X.VSTR: 'prehensile'

The following command displays the value of vstr based on the POINTER:


DBG> EXAMINE xptr->.vstr
POINTER\MAINPOINTER\XPTR->.VSTR: 'prehensile '

C.16.7.4 TREE and TREEPTR Variables

You can examine the contents of the nodes in a tree using the following syntax:


EXAMINE tree_variable([subscript],...)

You cannot deposit into a TREE variable.

If you specify the name of a tree with the EXAMINE command, the debugger displays the contents of all nodes and leaves of the tree. For example:


DBG> EXAMINE voters

You can specify an interior node by entering the subscript for that node. For example:


DBG> EXAMINE voters('salem')

You can examine the leaf node in a tree by specifying all subscripts leading to the desired leaf. For example:


DBG> EXAMINE voters('salem',ward2)

If you examine a TREEPTR variable, such as cityptr or wardptr, the debugger displays the address of that tree node. You examine what a TREEPTR variable is pointing to as follows:


DBG> EXAMINE cityptr->

C.16.7.5 RECORD and OVERLAY Variables

If you specify a RECORD by name with the EXAMINE command, all components of the RECORD are presented. To examine individual components of the RECORD, specify the full name of each component.

The general format is as follows:


EXAMINE recordname


EXAMINE recordname.componentname.componentname...

You examine an OVERLAY in the same way. All components are again presented; thus, if a four-byte region is a FILL(4), an INTEGER, and a VARYING STRING(2), the four bytes will be displayed three different ways.

C.17 Language UNKNOWN

The following subtopics describe debugger support for language UNKNOWN.

C.17.1 Operators in Language Expressions

Supported operators in language expressions for language UNKNOWN follow:
Kind Symbol Function
Prefix + Unary plus
Prefix - Unary minus (negation)
Infix + Addition
Infix - Subtraction
Infix * Multiplication
Infix / Division
Infix ** Exponentiation (VAX specific)
Infix & Concatenation
Infix // Concatenation
Infix = Equal to
Infix <> Not equal to
Infix /= Not equal to
Infix > Greater than
Infix >= Greater than or equal to
Infix < Less than
Infix <= Less than or equal to
Infix EQL Equal to
Infix NEQ Not equal to
Infix GTR Greater than
Infix GEQ Greater than or equal to
Infix LSS Less than
Infix LEQ Less than or equal to
Prefix NOT Logical NOT
Infix AND Logical AND
Infix OR Logical OR
Infix XOR Exclusive OR
Infix EQV Equivalence


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