[Dwarf-discuss] Proposal: Error: DW_OP_entry_value description and examples

[Kyle Huey]

On Tue, Aug 8, 2023 at 9:22 AM Metzger, Markus T via Dwarf-discuss <
dwarf-discuss@lists.dwarfstd.org> wrote:

> >### Section 2.5.1.7 Special Operations, p.37
> >
> >The first sentence of the description of DW_OP_entry_value reads:
> >
> >    The DW_OP_entry_value operation pushes the value that the described
> >    location held upon entering the current subprogram.
> >
> >A DWARF expression does not describe a location, so this should read:
> >
> >    The DW_OP_entry_value operation evaluates an expression or register
> >    location description as if it had been evaluated upon entering the
> >    current subprogram, and pushes the value of the expression or content
> >    of the register, respectively.
>
> Aren't register location descriptions the only thing that, given
> appropriate
> unwind rules, can actually be implemented?
>
> Should this be restricted to only allow register location descriptions?
>

There exist debuggers (e.g. Pernosco https://pernos.co/about/overview/)
that are capable of handling non-register location descriptions in the
past, so I would oppose any spec limitation on what DW_OP_entry_value can
evaluate.

- Kyle


> Regards,
> Markus.
> Intel Deutschland GmbH
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