||Cobol Data Types
||Accepted with modifications
Support for COBOL-specific data types is not available in DWARF.
Desirable capabilities include support for packed and unpacked
decimal, edited and fixed point types as well as COBOL "level-88"
A draft proposal for COBOL data types was sent to the DWARF list
by Bob Monteleone (then of Compaq) in December 2001. During
January 2002, there was significant discussion of alternative
In April 2002, Ron Brender distributed a copy of the final
specification that (then) Compaq had adopted. That specification
is attached below.
This specification is currently being used by two OS environments
- OpenVMS for Itanium Systems
- NonStop (formerly Tandem NSK) for Itanium Systems
OpenVMS support is currently in field test and expected to ship
by the end of the year. NonStop support is fully implemented in
internal development versions (but I am not aware of the rollout
ATTACHMENT ("The Proposal")
DWARF spec for COBOL support
22 April 2002
In order to support the COBOL language in DWARF, enhancements to the
DWARF V3 specification are necessary. Specifically, extensions are
required to describe decimal, packed decimal, edited and scaled
binary data types; also to describe 'level-88' conditions.
Five new base types and one new tag will be introduced to represent
the new COBOL types and level-88 conditions.
2 BASE TYPES
New base type values are needed for the DW_AT_encoding attribute to
represent fundamental COBOL types.
2.1 Packed Decimal And Zoned Decimal Types
The DW_ATE_CPQ_packed_decimal and DW_ATE_CPQ_zoned_decimal base
types are used to represent decimal string numeric data types;
packed and unpacked, and, signed and unsigned.
The DW_ATE_CPQ_packed_decimal and DW_ATE_CPQ_zoned_decimal base
types have a DW_AT_CPQ_decimal_sign, DW_AT_CPQ_digit_count and a
A DW_AT_CPQ_decimal_sign attribute is used to convey the
representation of the sign of the decimal type. Its integer
constant value is interpreted to mean that the type has a leading
overpunch, trailing overpunch, leading separate or trailing separate
sign representation or, alternatively, no sign at all.
The DW_AT_CPQ_digit_count attribute is an integer constant value
that represents the number of digits in an instance of the type.
The DW_AT_CPQ_decimal scale attribute is an integer constant value
that represents the exponent of the base ten scale factor to be
applied to an instance of the type. Zero scale puts the decimal
point immediately to the right of the least significant digit.
Positive scale moves the decimal point to the right and implies that
additional zero digits on the right are not stored in an instance of
the type. Negative scale moves the decimal point to the left; if
the absolute value of the scale is larger than the digit count, this
implies additional zero digits on the left not stored in an instance
of the type.
Values and Meanings for DW_AT_CPQ_decimal_sign
Sign is encoded in the most significant digit in a
Sign is encoded in the least significant digit in a
Sign is a '+' or '-' character to the left of the
most significant digit.
Decimal type: Sign is a '+' or '-' character to the
right of the least significant digit. Packed decimal
type: Least significant nibble contains a
target-dependent value indicating positive or
2.2 Edited Numeric And Edited Alphanumeric Types
The DW_ATE_CPQ_edited base type is used to represent a COBOL edited
numeric or alphanumeric data type.
The edited type entry has a DW_AT_CPQ_picture_string attribute whose
value is a null-terminated string containing the target-dependent
picture string associated with the type.
If the edited base type entry describes an edited numeric data type,
the edited type entry has a DW_AT_CPQ_digit_count and a
DW_AT_CPQ_decimal_scale attribute. These attributes are interpreted
as in the context of the DW_ATE_CPQ_packed_decimal and
DW_ATE_CPQ_zoned_decimal base types. If the edited type entry
describes an edited alphanumeric data type, the edited type entry
does not have these attributes.
The presence or absence of the DW_AT_CPQ_digit_count and
DW_AT_CPQ_decimal_scale attributes allows a debugger to easily
distinguish edited numeric from edited alphanumeric, although in
principle the digit count and scale are derivable by interpreting
the picture string.
2.3 Signed And Unsigned Fixed-Point Types
The DW_ATE_CPQ_signed_fixed and DW_ATE_CPQ_unsigned_fixed entries
describe signed and unsigned fixed-point binary data types,
The fixed binary type entries have a DW_AT_CPQ_digit_count attribute
with the same interpretation as described for the
DW_ATE_CPQ_packed_decimal and DW_ATE_CPQ_zoned_decimal base types.
For a data type with a decimal scale factor, the fixed binary type
entry has a DW_AT_CPQ_decimal_scale attribute with the same
interpretation as described for the DW_ATE_CPQ_packed_decimal and
DW_ATE_CPQ_zoned_decimal base types.
For a data type with a binary scale factor, the fixed binary type
entry has a DW_AT_CPQ_binary_scale attribute. The
DW_AT_CPQ_binary_scale attribute is an integer constant value that
represents the exponent of the base two scale factor to be applied
to an instance of the type. Zero scale puts the binary point
immediately to the right of the least significant bit. Positive
scale moves the binary point to the right and implies that
additional zero bits on the right are not stored in an instance of
the type. Negative scale moves the binary point to the left; if the
absolute value of the scale is larger than the number of bits, this
implies additional zero bits on the left not stored in an instance
of the type.
For a data type with an arbitrary scale factor, the fixed binary
type entry has a DW_AT_CPQ_small attribute. It references a
DW_TAG_constant entry with an arbitrary type attribute. The scale
factor value is interpreted in accordance with the value enumerated
in the DW_TAG_constant entry. The value represented is the product
of the integer value in memory and the associated contant entry for
The DW_TAG_CPQ_condition debugging information entry describes a
COBOL level-88 condition. A level-88 condition associates a data
item, called the conditional variable, with a set of one or more
constant values and/or value ranges. Semantically, the condition is
'true' if the conditional variable's value matches any of the
described constants, and the condition is 'false' otherwise.
If a name has been given to the condition, the condition entry has a
DW_AT_name attribute whose value is a null-terminated string giving
the condition name as it appears in the source program.
The condition entry's parent entry describes the conditional
variable; normally this will be a DW_TAG_variable or DW_TAG_member
entry. The type of the condition entry is derived from the
DW_AT_type attribute of the parent entry.
The condition entry owns DW_TAG_constant and/or DW_TAG_subrange_type
entries that describe the constant values associated with the
condition. If any child entry has a DW_AT_type attribute, that
attribute should describe a type compatible with the type derived
from the condition entry's parent.
For conditional variables with alphanumeric types, COBOL permits a
source program to provide ranges of alphanumeric constants in the
condition. Normally a subrange type entry does not describe ranges
of strings; however, it can be done using bounds' attributes that
are references to constant entries describing strings. A subrange
type entry may refer to constant entries that are siblings of the
subrange type entry.
Tags and Attributes
The "proposal" in issue 020401.1 is not quite a proper proposal
in that it uses the vendor-specific names adopted by (then)
Compaq which include "CPQ_" in the attribute and code names.
Clearly the "CPQ_" substrings should be removed.
One other naming change is recommended: the base type name
DW_ATE_CPQ_zoned_decimal have proven obscure and confusing. For
the DWARF standard, the name DW_ATE_numeric_string is much more
descriptive and suggestive.
Finally, the write-up does not propose where text should be
included. This can be handled as follows:
Proposal What Goes here in DWARF V3
-------- ---- ---------------------
1 list of base types Figure 12 (Sec 5.1, p64)
Add new DW_ATE codes in
Figure 23 (p141)
2.1 description of base Insert at end of 5.1
types (prior to Fig 12)
Create a new Figure
in Section 7.8 for the
Decimal Sign (DW_DS_*)
Note: while 2.1 has subsections, I don't propose
to add corresponding subsections to 5.1
3 Condition Insert as new 5.7 (and
renumber the following
in Figure 1 (p6) and
in Figure 16 (p127)
With these changes and supplemental information, 020401.1 should
be appropriate for consideration.
5/17/2005: Accepted with modifications:
Remove CPQ from names.
Replace "zoned decimal" with "decimal string".