Re: [PATCH 1/3] Add support for DW_OP_GNU_variable_value

Kevin Buettner
2018-08-23T21:12:45Z

On Wed, 22 Aug 2018 17:35:23 +0200
Tom de Vries <tdevries@suse.de> wrote:

> On 08/18/2018 10:31 PM, Kevin Buettner wrote:
> > This patch adds support for DW_OP_GNU_variable_value to GDB.
> >
> > Jakub Jelinek provides a fairly expansive discussion of this DWARF
> > expression opcode in his GCC patch...
> >
> > https://gcc.gnu.org/ml/gcc-patches/2017-02/msg01499.html
> >
> > It has also been proposed for addition to the DWARF Standard:
> >
> > http://www.dwarfstd.org/ShowIssue.php?issue=161109.2
>
> Hi,
>
> AFAIU from the discussion here (
> https://gcc.gnu.org/ml/gcc-patches/2018-08/msg01351.html ) if:
> - a DW_OP_GNU_variable_value refers to a die 'a', and
> - there's a die 'b' with abstract_origin 'a' that does have a
> DW_AT_location, and
> - die 'b' is 'in scope' in an evaluation context,
> then the evaluation of DW_OP_GNU_variable_value 'a' should return the
> value found at the DW_AT_location of die 'b'.
>
> I've written a gcc demonstrator patch to generate code like this for
> VLAs, and found that gdb master (containing this patch series) does not
> support this.
>
> Is this further support of DW_OP_GNU_variable_value something you're
> currently working on, or plan to work on?

Tom and I discussed this briefly on IRC. Tom says that he'll take
a look at it...

Kevin