[Dwarf-discuss] Proposal: Add support for "property" with getter/setter (based on Pascal properties)

[Martin]

Small correction

   property MyProp: integer read public MyFunc write MyMember;

Should be
   property MyProp: integer read public MyFunc write MyMember; default;

As I added the  DW_AT_Default_Property flag in the example.
In FreePascal, this would currently only be valid for properties with 
array-indexes, but may be extended in future. For the example it just 
shows where the attribute would go.



On 08/05/2024 12:35, Martin via Dwarf-discuss wrote:
> Here are 2 examples of what it would look like
> 
> ## Property with different visibility
> 
> ```
>    type
>      TFoo = class
>      private
>        MyMember: integer;
>        function MyFunc: integer;
>      protected
>        // "read public" is currently from oxygene, but may be added to 
> FreePascal
>        property MyProp: integer read public MyFunc write MyMember;
>      end;
> 
>      TBar = clall(TFoo)
>      public
>        property MyProp; // elevate to public
>      end;
> ```
> 
> ```
>    DW_TAG_Structure_type
>      DW_AT_Name :  "TFoo"
> L1:
>      DW_TAG_Member
>          DW_AT_Name            :  "MyMember"
>          DW_AT_Type            :  <...>
>          DW_AT_Member_location :  <...>
> L2:
>      DW_TAG_subprogram
>          DW_AT_Name            :  "MyFunc"
>          DW_AT_Type            :  <...>
> 
>      DW_TAG_Property
>          DW_AT_Name             :  "MyProp"
>          DW_AT_Type             :  <...>
>          DW_AT_Accessibility    :  DW_ACCESS_protected
>          DW_AT_Default_Property :  TRUE
>        DW_TAG_Property_Getter
>            DW_AT_Property_Forward :  reference to L2
>            DW_AT_Accessibility    :  DW_ACCESS_public
>        DW_TAG_Property_Setter
>            DW_AT_Property_Forward :  reference to L1
> 
>    DW_TAG_Structure_type
>      DW_AT_Name :  "TBar"
>      DW_TAG_Inheritance
>          <...>
>      DW_TAG_Property
>          DW_AT_Name             :  "MyProp"
>          DW_AT_Accessibility    :  DW_ACCESS_public
> ```
> 
> ## Property with access to nested field
> 
> 
> ```
>    type
>      TFoo = class
>        OtherData: DWORD;
>        FNested: record
>          MyMember: integer;
>        end;
>        property MyProp: integer read FNested.MyMember;
>      end;
> ```
> 
> ```
> L1:
>    DW_TAG_Structure_type
> L2:
>      DW_TAG_Member
>          DW_AT_Name            :  "MyMember"
>          DW_AT_Type            :  <...>
>          DW_AT_Member_location :  <...>    ! inside FNested
> 
>    DW_TAG_Structure_type
>      DW_AT_Name :  "TFoo"
>      DW_TAG_Member
>          DW_AT_Name :  "OtherData"
>      DW_TAG_Member
>          DW_AT_Name :  "FNested"
>          DW_AT_Type            :  reference to L1
>          DW_AT_Member_location :
>                DW_OP_plus_uconst 4             ! where 4 == offset of 
> MyMember in the instance data
> 
>      DW_TAG_Property
>          DW_AT_Name             :  "MyProp"
>          DW_AT_Type             :  <...>
>        DW_TAG_Property_Getter
>            DW_AT_Property_Forward :  reference to L2
>            DW_AT_Property_Object  :
>                DW_OP_push_object_address  ! maybe should be on stack by 
> default
>                DW_OP_plus_uconst 4        ! where 4 == offset of 
> MyMember in the instance data
>                                           ! There could be several 
> levels of nesting, so that expression could be more complex
> ```
> 
> In the example the property does not have a reference to FNested itself. 
> All it needs is the object_address of FNested, so it can calculate the 
> location of the referenced field MyMember (using the member_location).
> 
>