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From: "vries at gcc dot gnu.org" <sourceware-bugzilla@sourceware.org>
To: gdb-prs@sourceware.org
Subject: [Bug symtab/28200] DW_AT_ranges handling in partial_die_info::read
 does not handle discontinuous ranges
Date: Fri, 06 Aug 2021 11:57:08 +0000
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https://sourceware.org/bugzilla/show_bug.cgi?id=3D28200

--- Comment #2 from Tom de Vries <vries at gcc dot gnu.org> ---
Essentially, there are two interpretations of has_pc_info:
- this is not something to be ignored, build a symbol in the partial symbol
  table
- the field lowpc and highpc are valid.

The code:
...
            if (dwarf2_ranges_read (ranges_offset, &lowpc, &highpc, cu,
                                    nullptr, tag))
              has_pc_info =3D 1;
...
uses the first interpretation to fix the problem that a symbol is not liste=
d in
the partial symbol table.

Which also implies the second interpretation, which apparently usually does=
n't
cause much trouble, but evidently it does in combination with this workarou=
nd
for gcc 4.8 (see PR15231):
...
          scan_partial_symbols (first_die, &lowpc, &highpc,
                                cu_bounds_kind <=3D PC_BOUNDS_INVALID, cu);
...

So, at this point I see two potential solutions:
- add an address map along side lowpc/highpc and pass that instead of nullp=
tr
to=20
  dwarf2_ranges_read, and handle things from there-on
- split up the two interpretations of has_pc_info, say by adding
  highlowpc_valid (or have_ranges), and when encountering DW_AT_ranges
  just mark highlowpc_valid =3D 0 and has_pc_info =3D 1, and deferring read=
ing
  the ranges till we have the partial symtab address map to work with.

My guess is that the latter is more space-efficient.

--=20
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