gdbhooks: Update gdbhooks.py for recent tree_code_type changes [PR108634]

gdbhooks: Update gdbhooks.py for recent tree_code_type changes [PR108634]

On Mon, Mar 13, 2023 at 04:15:12PM -0400, Jason Merrill wrote:
> The r13-6577 change to use tree_code_type_tmpl in earlier C++ dialects broke
> gdbhooks, which expects tree_code_type to always be available.  I considered
> trying to make gdbhooks more robust, but it seemed simpler to define
> tree_code_type as a reference to the template.

As I said earlier, I think it is better to tweak gdbhooks.

The following patch does that, I've tested it now both with gcc 12 and
older gcc as system compiler and the patch fixed the latter while keeping
the former working as before.

2023-03-17  Jakub Jelinek  <jakub@redhat.com>

	PR plugins/108634
	* gdbhooks.py (TreePrinter.to_string): Wrap
	gdb.parse_and_eval('tree_code_type') in a try block, parse
	and eval 'tree_code_type_tmpl<0>::tree_code_type' instead if it
	raises exception.  Update comments for the recent tree_code_type
	changes.