Re: PROPOSAL: DW_AT_byte_size & DW_AT_bit_* as DW_FORM_ref*; allow on

[todd dot allen at ccur dot com (Todd Allen)]

> 
> I believe that this can be described completely within in the current
> standard, without requiring any changes.
> 
> We do not need to have every object able to specify a size and offset.
> This information is localized to two places:  the structure description
> and the base types.  There seems to be no need to scatter it everywhere.
> 

   My example didn't convey the full scope of the problem, then.  I'll
   explain further.

   Those two places do not allow the description a record object which is
   located at bit offset 3 of address ..., and has a bit size of 5.

   The object is not a component, and the record type isn't a base type.

   The issue is that Ada permits many more objects within a program to have
   bit offsets and bit sizes than just base type scalars or components of
   records.

   Allowing DW_AT_byte_size, DW_AT_bit_size, and DW_AT_bit_offset on objects
   isn't strictly necessary.  Merely allowing them on all types would
   suffice.  I concede that.  But it will cause DWARF bloat.  Allowing them
   on objects reduces the bloat.

>
> Also, I believe that a location expression would address your concerns.
> 

   DW_AT_bit_offset does not permit a location expression.  If it did, then
   technically allowing references wouldn't be necessary.  But if a reference
   is allowed, it would permit debuggers to give better descriptions of the
   location, since it could use the name or description of the referenced
   entity.

-- 
Todd Allen
Concurrent Computer Corporation