Issue 090402.2: Clarify DW_TAG_condition_name
In section 5.7 Condition Entries, the normative text currently reads:
The DW_TAG_condition debugging information entry describes a COBOL
level-88 condition. 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.
There are a few problems with this description.
1. The type "derived from" the parent is not well defined. In particular
what happens when the parent has an array type is not specified, and
it needs to be because it's not obvious.
2. The "type of the condition entry" is actually best described as
boolean, and is not interesting (so don't bother describing it at
all). What matters is the relationship between the type of the
conditional variable and the type(s) of the constant(s).
3. Normative text explicitly mentions COBOL.
I propose to replace the normative text with the following.
The DW_TAG_condition debugging information entry describes a logical
condition that tests whether a given data item's value matches one
of a set of constant values. 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, DW_TAG_member or
DW_TAG_formal_parameter entry. If the parent entry has an array
type, the condition can test any invididual element, but not the
array as a whole. The condition entry implicitly specifies a
"comparison type" that is the type of an array element if the parent
has an array type, otherwise it is the type 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 comparison type;
otherwise the child's type is the same as the comparison type.
The non-normative text would remain as is.
--
Accepted July 7, 2009.
