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

Frank Ch. Eigler fche at redhat.com
Thu May 28 07:59:01 PDT 2009


Hi -

On Thu, May 28, 2009 at 02:57:08AM -0700, Michael Eager wrote:
> [...]
>> This problem (unable to retrieve variable values) raises two questions:
>> 1. Does it mean that compiling with -O2 option removes some of the
>> information needed by DWARF library functions?
>
> [...]  DIEs for variables which do not have DW_AT_location
> attributes do not have physical locations.  Your crash dump utility
> should not attempt to find the locations or print the values for
> these variables.

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.

- FChE



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