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From: "vries at gcc dot gnu.org" <sourceware-bugzilla@sourceware.org>
To: gdb-prs@sourceware.org
Subject: [Bug symtab/26327] GDB hangs in get_builder() due to recursive
 ancestor pointers
Date: Mon, 19 Oct 2020 12:21:22 +0000
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https://sourceware.org/bugzilla/show_bug.cgi?id=3D26327

Tom de Vries <vries at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |keiths at redhat dot com,
                   |                            |tromey at sourceware dot o=
rg

--- Comment #6 from Tom de Vries <vries at gcc dot gnu.org> ---
Tentative patch, prevents introducing cycles in ancestor chain:
...
diff --git a/gdb/dwarf2/read.c b/gdb/dwarf2/read.c
index 37409c5c3f..72e5446b8b 100644
--- a/gdb/dwarf2/read.c
+++ b/gdb/dwarf2/read.c
@@ -22947,7 +22947,19 @@ follow_die_offset (sect_offset sect_off, int
offset_in_dwz,
   temp_die.sect_off =3D sect_off;

   if (target_cu !=3D cu)
-    target_cu->ancestor =3D cu;
+    {
+      bool cycle_p =3D false;
+      for (struct dwarf2_cu *tmp =3D cu->ancestor; tmp; tmp =3D tmp->ances=
tor)
+       {
+         if (tmp !=3D target_cu)
+           continue;
+
+         cycle_p =3D true;
+         break;
+       }
+      if (!cycle_p)
+       target_cu->ancestor =3D cu;
+    }

   return (struct die_info *) htab_find_with_hash (target_cu->die_hash,
                                                  &temp_die,
@@ -24256,7 +24268,8 @@ dwarf2_cu::dwarf2_cu (dwarf2_per_cu_data *per_cu,
     producer_is_icc (false),
     producer_is_icc_lt_14 (false),
     producer_is_codewarrior (false),
-    processing_has_namespace_info (false)
+    processing_has_namespace_info (false),
+    ancestor (nullptr)
 {
 }

...

--=20
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