[Dwarf-Discuss] Default Location List Entry Issue 130121.1

Frank Ch. Eigler fche at redhat.com
Wed Apr 23 05:49:54 PDT 2014


Hi -

On Wed, Apr 23, 2014 at 01:46:30PM +0200, Mark Wielaard wrote:
> [...]
> > > So if a producer wants to take advantage of a default location list
> > > entry to encode a smaller location list for an object, then how should
> > > it present to the consumer the same "not available" information?
> > 
> > I think that this is an unusual situation.  Can you describe when this
> > might be the case?
> 
> I think it is not such an uncommon situation. When a compiler inlines
> part of a function somewhere else that often seems to create interesting
> ranges and locations. [...]

It sounds like the situation for gcc's -g -O0 (unoptimized) case,
where a default location is emitted for a variable DIEs, but that
location is only valid/accurate outside the prologue/epiogue areas.
(The pc-address ranges of those areas are not noted in DWARF, and this
requires consumers like gdb & systemtap to employ heuristics.)

- FChE



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