[Dwarf-discuss] Proposal/clarification: "inherited" subrange bounds

[Cary Coutant]

Alexandre,

It sounds like you still would like to propose a change to DWARF. Can I ask
you to come back with a formal proposal? It's OK if you're not sure of one
alternative over another, but I'd like to see something more specific in
terms of what changes you'd like to make.

-cary


On Tue, Jul 30, 2024 at 6:22 PM Alexandre Oliva via Dwarf-discuss <
dwarf-discuss@lists.dwarfstd.org> wrote:

> On Jul 29, 2024, David Blaikie <dblaikie@gmail.com> wrote:
>
> >> The situation is not very different, but in Ada one can specify the
> >> target size (in bits) for the type (which may require biased
> >> representations, but that's besides the point).  Despite the specified
> >> size, standalone variables and members of unpacked types use full
> >> storage units, unless packing is requested.  See
> >> e.g.
> >>
> https://gcc.gnu.org/git/?p=gcc.git;a=blob;f=gcc/testsuite/gnat.dg/bias1.adb
>
> > I see, so do I understand correctly that you'd prefer not to use the
> > bitfield style representation, because it'd be repetitious?
>
> There's that (Dwarf aims for compactness), but there's also the fact
> that the type size is explicitly specified as the smaller bit size, so a
> proper representation of that type would carry that piece of
> information.  ISTM that ideally the larger, full-unit-sized variant
> would be the one using explicit sizes or a separate type variant
> inheriting the same bounds.
>
> But the problem I see, and try to raise in this thread, is that there's
> no way for a subrange type to inherit bounds from another subrange type,
> which once again plays against compactness.
>
> --
> Alexandre Oliva, happy hacker
> https://FSFLA.org/blogs/lxo/
>    Free Software Activist                           GNU Toolchain Engineer
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