DWARF: add DW_AT_encoding attributes for DW_TAG_enumeration_type DIEs
Currently, the DWARF description does not specify the signedness of the
representation of enumeration types. This is a problem in some
contexts where DWARF consumers need to determine if value X is greater
than value Y.
For instance in Ada:
type Enum_Type is ( A, B, C, D);
for Enum_Type use (-1, 0, 1, 2);
type Rec_Type (E : Enum_Type) is record
when A .. B => null;
when others => B : Booleann;
end record;
The above can be described in DWARF the following way:
DW_TAG_enumeration_type(Enum_Type)
| DW_AT_byte_size: 1
DW_TAG_enumerator(A)
| DW_AT_const_value: -1
DW_TAG_enumerator(B)
| DW_AT_const_value: 0
DW_TAG_enumerator(C)
| DW_AT_const_value: 1
DW_TAG_enumerator(D)
| DW_AT_const_value: 2
DW_TAG_structure_type(Rec_Type)
DW_TAG_member(E)
| DW_AT_type: <Enum_Type>
DW_TAG_variant_part
| DW_AT_discr: <E>
DW_TAG_variant
| DW_AT_discr_list: DW_DSC_range 0x7f 0
DW_TAG_variant
| DW_TAG_member(b)
DWARF consumers need to know that enumerators (A, B, C and D) are signed
in order to determine the set of E values for which Rec_Type has a B
field. In practice, they need to know how to interpret the 0x7f LEB128
number above (-1, not 127).
When in non-strict DWARF mode, this patch adds a DW_AT_encoding
attribute to generated DW_TAG_enumeration_type DIEs to make this
signedness explicit.
gcc/
* dwarf2out.c (gen_enumeration_type_die): When
-gno-strict-dwarf, add a DW_AT_encoding attribute.
git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/trunk@244015 138bc75d-0d04-0410-961f-82ee72b054a4