[PATCH] Fix crash in DWARF indexer

[Tom Tromey <tromey@adacore.com>]

Iain pointed out a crash in the DWARF indexer when run on a certain D
program.  The DWARF in this case has a nameless enum class; this
causes an assertion failure.

This patch arranges to simply ignore such types.  The fact that an
enum class is nameless in this case appears to be a compiler bug.

Bug: https://sourceware.org/bugzilla/show_bug.cgi?id=32518
---
 gdb/dwarf2/read.c                          | 35 ++++++------
 gdb/testsuite/gdb.dwarf2/nameless-enum.exp | 62 ++++++++++++++++++++++
 2 files changed, 82 insertions(+), 15 deletions(-)
 create mode 100644 gdb/testsuite/gdb.dwarf2/nameless-enum.exp

diff --git a/gdb/dwarf2/read.c b/gdb/dwarf2/read.c
index a008f0ee88b..034bba01ad6 100644
--- a/gdb/dwarf2/read.c
+++ b/gdb/dwarf2/read.c
@@ -16814,22 +16814,27 @@ cooked_indexer::index_dies (cutu_reader *reader,
 		 whether we're reading an "enum class".  If so, we use
 		 the enum itself as the parent, yielding names like
 		 "enum_class::enumerator"; otherwise we inject the
-		 names into our own parent scope.  */
-	      {
-		std::variant<const cooked_index_entry *,
-			     parent_map::addr_type> recurse_parent;
-		if (is_enum_class)
-		  {
-		    gdb_assert (this_entry != nullptr);
-		    recurse_parent = this_entry;
-		  }
-		else if (defer != 0)
-		  recurse_parent = defer;
-		else
-		  recurse_parent = this_parent_entry;
+		 names into our own parent scope.
 
-		info_ptr = recurse (reader, info_ptr, recurse_parent, fully);
-	      }
+		 Some versions of gdc could emit an "enum class"
+		 without a name, which is nonsensical.  These are
+		 skipped.  */
+	      if (!is_enum_class || this_entry != nullptr)
+		{
+		  std::variant<const cooked_index_entry *,
+			       parent_map::addr_type> recurse_parent;
+		  if (is_enum_class)
+		    {
+		      gdb_assert (this_entry != nullptr);
+		      recurse_parent = this_entry;
+		    }
+		  else if (defer != 0)
+		    recurse_parent = defer;
+		  else
+		    recurse_parent = this_parent_entry;
+
+		  info_ptr = recurse (reader, info_ptr, recurse_parent, fully);
+		}
 	      continue;
 
 	    case DW_TAG_module:
diff --git a/gdb/testsuite/gdb.dwarf2/nameless-enum.exp b/gdb/testsuite/gdb.dwarf2/nameless-enum.exp
new file mode 100644
index 00000000000..c2eda994984
--- /dev/null
+++ b/gdb/testsuite/gdb.dwarf2/nameless-enum.exp
@@ -0,0 +1,62 @@
+# Copyright 2025 Free Software Foundation, Inc.
+
+# This program is free software; you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation; either version 3 of the License, or
+# (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+# Test a nameless "enum class".  This is nonsensical but previously
+# made gdb crash.
+
+load_lib dwarf.exp
+require dwarf2_support
+
+standard_testfile main.c nameless-enum.S
+
+set asm_file [standard_output_file $srcfile2]
+Dwarf::assemble $asm_file {
+    global srcfile
+
+    cu {} {
+	DW_TAG_compile_unit {
+	    {DW_AT_language @DW_LANG_D}
+	    {DW_AT_name	$srcfile}
+	    {DW_AT_comp_dir /tmp}
+	} {
+	    declare_labels integer_label
+
+	    integer_label: DW_TAG_base_type {
+		{DW_AT_byte_size 4 DW_FORM_sdata}
+		{DW_AT_encoding	 @DW_ATE_signed}
+		{DW_AT_name	 int}
+	    }
+
+	    DW_TAG_enumeration_type {
+		{DW_AT_type :$integer_label}
+		{DW_AT_enum_class 1 DW_FORM_flag}
+	    } {
+		DW_TAG_enumerator {
+		    {DW_AT_name VALUE}
+		    {DW_AT_const_value 17 DW_FORM_sdata}
+		}
+	    }
+	}
+    }
+}
+
+if {[prepare_for_testing "failed to prepare" ${testfile} \
+	 [list $srcfile $asm_file] {nodebug}]} {
+    return -1
+}
+
+# The bug was a crash, so just do anything here to verify gdb is still
+# alive.
+gdb_test "print 23" " = 23"
-- 
2.47.0