[Dwarf-discuss] Encoding variant records: request for clarification.

[Nettleton, Brian]

The example in Appendix D section D.2.2 shows how to encode Data and
Name.  Something like the following for the variant:

    DW_TAG_structure_type
        DW_AT_name "R"

1$:     DW_TAG_member
            DW_AT_name "N" 

        ...
        DW_TAG_variant_part
            DW_AT_discr reference to 1$

            DW_TAG_variant
                DW_AT_discr_value 0

                DW_TAG_member
                    DW_AT_name "Name"
                    [type info references 1$ like appendix example]

            DW_TAG_variant
                DW_AT_discr_list block DW_DSC_range 1 20

                DW_TAG_member
                    DW_TAG_name "Id"

                DW_TAG_member
                    DW_TAG_name "Port"

           DW_TAG_variant
                [this variant is empty]




-Brian Nettleton              



> -----Original Message-----
> From: dwarf-discuss-bounces at lists.freestandards.org 
> [mailto:dwarf-discuss-bounces at lists.freestandards.org] On 
> Behalf Of Paul Hilfinger
> Sent: Friday, August 18, 2006 1:11 AM
> To: dwarf-discuss at lists.freestandards.org
> Subject: [Dwarf-discuss] Encoding variant records: request 
> for clarification.
> 
> 
> I'm finding the description of variants a little difficult to
> interpret and apply, and I wonder if someone could supply me with an
> example.  Let's consider specifically the Ada record type R,
> defined
> 
>     type R (N : Integer) is record
>        Data : String (1 .. N);
>        case N is
>        when 0 =>
>            Name : String (1 .. N);
>        when 1..20 =>
>            Id, Port : Integer;
>        when others =>
>            null;
>        end case;
>     end record;
> 
> N here is basically a member of R.  As you can see, it is referred to
> in Data.  According to the standard, however, there is ALSO a child of
> the variant part for N.  What is the relationship between the two (the
> child of R representing N and the child of the variant child of R
> representing N)?  How exactly is type R to be encoded?
> 
> Thanks in advance.
> 
> Paul Hilfinger
> AdaCore, Inc. & UC Berkeley
> 
> 
>      
> 
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