[PATCH] D28303: Add iterator support to DWARFDie to allow child DIE iteration.

[Greg Clayton via llvm-commits]

> On Jan 5, 2017, at 1:20 PM, Adrian Prantl <aprantl at apple.com> wrote:
> 
>> 
>> On Jan 5, 2017, at 1:16 PM, David Blaikie <dblaikie at gmail.com> wrote:
>> 
>> 
>> 
>> On Thu, Jan 5, 2017 at 12:38 PM Greg Clayton <clayborg at gmail.com> wrote:
>>>> On Jan 5, 2017, at 11:33 AM, David Blaikie <dblaikie at gmail.com> wrote:
>>>> 
>>>> Looks like it might be missing test coverage for the "skip null" in the iterator ctor.
>>> 
>>> I have added a test for this that I’ll post in the next diff.
>>> 
>>>> Also - I'd like a good sense of what's going to happen with the child iteration inconsistency between this and the getChild/Sibling API before this is committed.
>>> 
>>> DWARFDie::getSibling() will still return a NULL DIE at the end. Iteration won’t. What are you suggesting happen?
>>> 
>>> We could add a bool to the getSibling() API:
>>> 
>>> DWARFDie DWARFDie::getSibling(bool IncludeNull = false);
>>> 
>>> Then we could get rid of the code in DWARFDie::iterator and have it call DWARFDie::getSibling() with false. The DWARFDie::dump would call it with true. 
>>> 
>>> Am I missing something? Let me know what you were thinking.
>> 
>> Mostly I was hoping/thinking/suggesting removing the null DIEs as you'd suggested previously.
>> 
>> It's only a couple of places - one in obj2yaml and one in dwarfdump, yes? It doesn't seem worth complicating the libDebugInfo APIs for those two use cases, I think?
>> 
>> Adrian - any thoughts/preferences here?
> 
> Removing the NULL DIEs make computing the offsets for printing in dwarfdump more complicated but it does save about 50MB when parsing something the size of clang. I would like to defer to Greg here since he actually looked at much work / extra overhead that would be.

It really comes down to the obj2yaml and yaml2obj making things hard for removing the NULL DIEs since they iterate over the raw DIE array. Let me get this in and I will work on that patch once again and get things right.

Greg