[Dwarf-Discuss] Does gcc optimization impacts retriving Dwarf information?

Mark Wielaard mjw at redhat.com
Fri May 29 02:41:42 PDT 2009


(Resent, now actually subscribed to the list from the correct address)

On Fri, 2009-05-29 at 14:28 +0530, M. Mohan Kumar wrote:
> >> That's all true in the abstract, but modern gcc has been known to
> >> abscond with variable location data even for values that are
> >> live/recomputable.  This is the main reason why the VTA (and
> >> debuglocus and other) gcc projects are under way -- to represent the
> >> maximum possible conceptual data, despite -O2 etc.
> 
> Frank, Will VTA/debuglocus have the dwarf compatibility (i.e. it does not
> need modification to existing applications using libdwarf APIs)?
> 
> When can we expect this features (VTA/debuglocus) integrated into mainline
> gcc?

Yes, it will output (hopefully better/more complete) dwarf information.
I don't know the schedule details of when this will land in gcc
mainline. But the ideas behind how to improve the tracking of debug
locations for variables in gcc can be found in this paper from Alexandre
Olivia: http://www.lsd.ic.unicamp.br/~oliva/papers/vta/slides.pdf
And on this GCC wiki page:
http://gcc.gnu.org/wiki/Var_Tracking_Assignments

DebugLocus is an alternative idea on an implementation to improve
tracking debug information from Andrew MacLeod described here:
http://gcc.gnu.org/wiki/AndrewMacLeod/debuglocus

Cheers,

Mark




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