[Dwarf-Discuss] decoding of form entries

Ron Brender ron.brender at charter.net
Tue Aug 3 09:33:46 PDT 2010


I am in agreement with Todd and David G that the intent for the 
attributes discussed in 2.19 is that the reference will identify a DIE 
for an object (variable, parameter, constant), whose contents is the 
value of the original attribute.

In no case was it ever envisioned, so far as I recall, that the target 
DIE would need to have a "matching" attribute.

David A also has a point about the wording being not quite consistent 
with intended usage, mixing up our conventions for entry versus entity. 
Something like the following as a replacement for the second bullet in 
2.19 might be better, or at least a starting point for discussion:

   . "For a reference, the reference identifies another debugging 
information entry, typically corresponding to a variable, constant or 
other object; the value of the other entity specifies the value of the 
attribute."

Moreover,scanning through the list of DIE kinds, I actually don't see 
any ones other than the various object kinds that can actually make 
sense in the context of Section 2.19. This suggests that without loss of 
generality the second bullet can be made specific to objects as in

   . "For a reference, the reference identifies another debugging 
information entry corresponding to a variable, constant or other object; 
the contents of that object specifies the value of the attribute."

Note that this does not restrict what references can refer to in 
general, just what they can refer for the attributes discussed in 
Section 2.19.

Such are my 2 bits...

Ron

---------------------
David Anderson wrote:
> On 08/02/2010 12:58 AM, Mathieu Lacage wrote:
>> Something that has been bugging me for a while is that I am not sure I
>> understand the meaning of 2.19  p 40 (dw4) that talks about how to
>> retrieve the value associated to an attribute in an entry. It says:
>>
>> "For a reference, the value is a reference to another entity whose
>> value is the value of the
>> attribute."
> 
> The quoted sentence from DWARF4 confuses me too.
> 
> A 'reference' is defined in 'classes of attribute value', Figure 3, as 
> referring to
> a debugging information entry or a type signature.
> 
> The word 'entity' is used to refer to data in the running application, 
> as in
> Sec 2.1:
> " An entry, or group of entries together, provide a description of a
> corresponding entity in the source program. "
> Or elsewhere "entity in memory"  or "Program entity".
> 
> Others seem to think the 'entity' is another DIE (indeed
> I think that was the intent), but I wonder what
> in DWARF4 terminology supports that interpretation of that word 'entity' 
> in 2.19.
> 
> The sentence seems(?) to be inconsistent with the rest of DWARF4 in its
> use of 'entity'.
> 
> David Anderson
> 






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