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From: "vries at gcc dot gnu.org" <sourceware-bugzilla@sourceware.org>
To: dwz@sourceware.org
Subject: [Bug default/24399] New: Dead code in partition_dups_1
Date: Tue, 01 Jan 2019 00:00:00 -0000
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https://sourceware.org/bugzilla/show_bug.cgi?id=3D24399

            Bug ID: 24399
           Summary: Dead code in partition_dups_1
           Product: dwz
           Version: unspecified
            Status: NEW
          Severity: normal
          Priority: P2
         Component: default
          Assignee: nobody at sourceware dot org
          Reporter: vries at gcc dot gnu.org
                CC: dwz at sourceware dot org
  Target Milestone: ---

There's this clause in partition_dups_1:
...
      /* If during second_phase there are some DIEs we want to force=20=20=
=20=20=20=20=20=20=20=20=20=20
         into a partial unit because they are referenced from something=20=
=20=20=20=20=20=20=20=20
         already forced into a partial unit, but also some DIEs with=20=20=
=20=20=20=20=20=20=20=20=20=20
         the same set of referrers, try to see if we can put also those=20=
=20=20=20=20=20=20=20=20
         into the partial unit.  They can be put there only if they=20=20=
=20=20=20=20=20=20=20=20=20=20=20
         don't refer to DIEs that won't be put into partial units.  */
      if (second_phase && force && force < j - k)
        {
...

It seems that the clause is dead. I can't trigger this abort in the test
suites:
...
diff --git a/dwz.c b/dwz.c
index 6b6a33e..c44d53d 100644
--- a/dwz.c
+++ b/dwz.c
@@ -5349,6 +5349,7 @@ partition_dups_1 (dw_die_ref *arr, size_t vec_size,
         don't refer to DIEs that won't be put into partial units.  */
       if (second_phase && force && force < j - k)
        {
+         abort ();
          /* First optimistically assume all such DIEs can be put there,
             thus mark all such DIEs as going to be included, so that
             even if one of those DIEs references another one from those
...

There's a loop just before this optimization:
...
      for (k =3D i; k < j; k++)
        {
          if (second_phase && arr[k]->die_ref_seen)
            force++;
          size +=3D calc_sizes (arr[k]);
          for (ref =3D arr[k]->die_parent;
               ref->die_named_namespace && ref->die_dup =3D=3D NULL;
               ref =3D ref->die_parent)
            {
              ref->die_dup =3D arr[k];
              namespaces++;
            }
        }
...
and it does not contain a break, so the expected end status will be k =3D=
=3D j.

So, the condition 'force < j - k' with force >=3D will always evaluate to f=
alse.

--=20
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