Re: GDB 13 Release 2022-09-11 update

[Tom Tromey <tom@tromey.com>]

Tom> Perhaps it would be worth clarifying the status of support for .gdb_index.

Tom> It is the defacto standard for the index cache, but ada support is
Tom> broken ( https://sourceware.org/bugzilla/show_bug.cgi?id=29179 ).

Tom> Do we want to fix this?

Tom> Do we want to deprecate .gdb_index and start using .debug_names for
Tom> the index cache?

Tom> Or are we fine with the status quo (which then might need documenting)?

My impression is that .gdb_index never really worked correctly for Ada.
So, while that is a regression of sorts, since the feature isn't really
usable for Ada in general, it doesn't seem worthwhile to fix it.

I did make .debug_names work for Ada.  See commit 3b00ef10a2a ("Add Ada
support for .debug_names").  I'm not at my work machine right now but
IIRC this is tested internally.

As for the overall plan, my view is:

* .gdb_index is (or should be) deprecated.  It was good but now we can
  do better.  However...

* In order to switch over fully, we have to fix the bugs in .debug_names.
  Fixing the writing side is easy (I have a patch somewhere) but I
  haven't worked on the reader yet.

* Once that is done we could switch over the index cache, but this also
  requires some more work to handle the situation where the index needs
  a string that isn't already in .debug_str.

I don't mind if this situation is documented.  We could even make
.gdb_index writing fail for Ada, though it seems to me that for the
index cache it is better to just fail silently.  Based on the Ada
programs I've seen, the new DWARF reader seems plenty fast enough
anyway.

Tom