There are several ways of changing the type associated with
a program location so that you can display the data at that
location in another data format:
o To change the default type for all locations that do not have
a symbolic name, you can specify a new type with the SET TYPE
command.
o To change the default type for all locations (both those that
do and do not have a symbolic name), you can specify a new
type with the SET TYPE/OVERRIDE command.
o To override the type currently associated with a particular
location for the duration of a single EXAMINE command, you can
specify a new type by using a type qualifier (/ASCII:n, /BYTE,
/TYPE=(name), and so on). Most qualifiers for the EXAMINE
command are type qualifiers.
The debugger can interpret and display integer data in any one of
four radixes: binary, decimal, hexadecimal, and octal.
The default radix for both data entry and display is decimal for
most languages. The exceptions are BLISS and MACRO, which have a
default radix of hexadecimal.
The EXAMINE command has four radix qualifiers (/BINARY, /DECIMAL,
/HEXADECIMAL, /OCTAL) that enable you to display data in another
radix. You can also use the SET RADIX and SET RADIX/OVERRIDE
commands to change the default radix.
In addition to the type and radix qualifiers, the EXAMINE command
has qualifiers for other purposes:
o The /SOURCE qualifier enables you to identify the line of
source code corresponding to a line number, routine name,
label, or any other address expression that is associated with
an instruction rather than data.
o The /[NO]LINE and /[NO]SYMBOLIC qualifiers enable you to
control the symbolization of address expressions.
The EXAMINE command sets the current entity built-in symbols
%CURLOC and period (.) to the location denoted by the address
expression specified. Logical predecessors (%PREVLOC or the
circumflex character (^)) and successors (%NEXTLOC) are based
on the value of the current entity.
The /VARIANT qualifier enables the debugger to display the
correct item when it encounters an anonymous variant.
In a C program, a union contains members, only one of which is
valid at any one time. When displaying a union, the debugger does
not know which member is currently valid. In a PASCAL program,
a record with a variant part contains variants, only one of
which is valid at any one time. When displaying a record with an
anonymous variant part, the debugger does not know which variant
is currently valid, and displays all variants by default.
You can use the /VARIANT qualifier of the EXAMINE command to
select which member of a union (C program) or anonymous variant
(PASCAL program) to display. The format is as follows:
DBG> EXAMINE /VARIANT=variant-selector address-expression
DBG> EXAMINE /VARIANT=(variant-selector,...) address-expression
The variant selector variant-selector specifies a name, a
discriminant (PASCAL only), or a position; that is, one of the
following:
o NAME = name-string
o DISCRIMINANT = expression
o POSITION = expression
The /VARIANT qualifier takes a list of zero or more variant
selectors. /VARIANT without any variant selectors is the
default: the first variant of all anonymous variant lists will
be displayed.
Each variant selector specifies either the name, the
discriminant, or the position of the variant to be displayed.
The debugger uses the variant selector as follows:
1. If the debugger encounters an anonymous variable list while
displaying address-expression, the debugger uses the variant
selector to choose which variant to display.
2. Each time the debugger encounters an anonymous variant list,
it attempts to use the next variant selector to choose which
variant to display. If the variant selector matches one of the
variants of the variant list (union), the debugger displays
that variant.
3. The debugger walks the structure top-to-bottom, depth first,
so that children are encountered before siblings.
4. If the debugger encounters an anonymous variant list and does
not have a variant selector to match it with, the debugger
displays the first variant.
5. If the variant selector does not match any of the variants of
an anonymous variant list, the debugger displays a single line
to indicate that. This is similar to what the debugger does if
the discriminant value fails to match any of the variants in a
discriminated variant list. . For example:
[Variant Record omitted - null or illegal Tag Value: 3]
A name specifies a name string. A name matches a variant if that
variant contains a field with the name specified by name.
A discriminant specifies a language expression that must be
type compatible with the tag type of the variant part it is
meant to match. The discriminant expression matches a variant
if it evaluates to a value in the variant's case-label list.
Discriminants apply only to Pascal programs, because C and C++
unions do not have discriminants.
A positional-selector specifies a language expression, which
should evaluate to a integer between 1 and N, where N is the
number of variants in a variant list. A positional-selector that
evaluates to I specifies that the Ith variant is to be displayed.
You can use asterisk (*) as a wildcard, which matches all
variants of an anonymous variant list.
Each of these variant selectors can be used to match all
variants. In particular, each of the following variant selectors
indicates that all of the variants of the first anonymous variant
list are to be displayed.
/VAR=D=*
/VAR=N=*
/VAR=P=*
The variant selectors can themselves contain a list of selectors.
For example, the following commands all mean the same thing.
EXAMINE /VARIANT=(DIS=3,DIS=1,DIS=54) x
EXAMINE /VARIANT=(DIS=(3,1,54)) x
EXAMINE /VARIANT=DIS=(3,1,54) x
You can specify a a single discriminant or position value without
parentheses if the value is a simple decimal integer. To use
a general expression to specify the value, you enclose the
expression in parentheses. In the following list of commands,
the first four are legal while the last three are not.
EXAMINE /VARIANT=POS=3
EXAMINE /VARIANT=POS=(3) ! parentheses unnecessary
EXAMINE /VARIANT=(POS=(3)) ! parentheses unnecessary
EXAMINE /VARIANT=(POS=3) ! parentheses unnecessary
EXAMINE /VARIANT=(POS=foo) ! parentheses necessary
EXAMINE /VARIANT=POS=(foo) ! parentheses necessary
EXAMINE /VARIANT=(POS=3-1) ! parentheses necessary
Related Commands:
CANCEL TYPE/OVERRIDE
DEPOSIT
DUMP
EVALUATE
SET MODE [NO]OPERANDS
SET MODE [NO]SYMBOLIC
(SET,SHOW,CANCEL) RADIX
(SET,SHOW) TYPE