[gdb/testsuite] Add gdb.dwarf2/clang-debug-names.c

Add test-case with .debug_names section using DW_FORM_ref4.

There's currently no support for .debug_names in the dwarf assembler, so we
use plain _emit rather than something more structured.

Consequently, we cannot use regular declare_labels-generated labels to refer
from .debug_names to .debug_info.  Instead, we use labels with a
predefined name, which we generate using _compute_label, and then define using
define_label.

This is the test-case for PR25952, so kfail the corresponding test.

Tested on x86_64-linux.

gdb/testsuite/ChangeLog:

2020-05-08  Tom de Vries  <tdevries@suse.de>

	* gdb.dwarf2/clang-debug-names.c: New test.
	* gdb.dwarf2/clang-debug-names.exp: New file.

3 files changed, 186 insertions, 0 deletions

diff --git a/gdb/testsuite/ChangeLog b/gdb/testsuite/ChangeLog
index a2e0d87e89d..49445fa3316 100644
--- a/gdb/testsuite/ChangeLog
+++ b/gdb/testsuite/ChangeLog
@@ -1,3 +1,8 @@
+2020-05-08  Tom de Vries  <tdevries@suse.de>
+
+	* gdb.dwarf2/clang-debug-names.c: New test.
+	* gdb.dwarf2/clang-debug-names.exp: New file.
+
 2020-05-06  Simon Marchi  <simon.marchi@efficios.com>
 
 	* gdb.arch/amd64-prologue-skip-cf-protection.exp: New file.
diff --git a/gdb/testsuite/gdb.dwarf2/clang-debug-names.c b/gdb/testsuite/gdb.dwarf2/clang-debug-names.c
new file mode 100644
index 00000000000..d66c192dbf3
--- /dev/null
+++ b/gdb/testsuite/gdb.dwarf2/clang-debug-names.c
@@ -0,0 +1,25 @@
+/* This testcase is part of GDB, the GNU debugger.
+
+   Copyright 2020 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/>.  */
+
+int
+main (void)
+{
+  asm ("main_label: .globl main_label");
+  int sum, a, b;
+  sum = a + b;
+  return sum;
+}
diff --git a/gdb/testsuite/gdb.dwarf2/clang-debug-names.exp b/gdb/testsuite/gdb.dwarf2/clang-debug-names.exp
new file mode 100644
index 00000000000..8bd60401c46
--- /dev/null
+++ b/gdb/testsuite/gdb.dwarf2/clang-debug-names.exp
@@ -0,0 +1,156 @@
+# Copyright 2020 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/>.
+
+load_lib dwarf.exp
+
+# This test can only be run on targets which support DWARF-2 and use gas.
+if {![dwarf2_support]} {
+    return 0
+}
+
+standard_testfile clang-debug-names.c clang-debug-names-debug.S
+
+# Set up the DWARF for the test.
+
+set main_str_label [Dwarf::_compute_label info_string3]
+set int_str_label [Dwarf::_compute_label info_string4]
+set main_die_label [Dwarf::_compute_label main_die_label]
+set int_die_label [Dwarf::_compute_label int_die_label]
+
+set debug_str \
+    [list \
+         "$main_str_label:" \
+         "  .asciz \"main\"" \
+         "$int_str_label:" \
+         "  .asciz \"int\""]
+
+set debug_names \
+    [list \
+         "  .4byte  .Ldebug_names_end - .Ldebug_names_start" \
+         ".Ldebug_names_start:" \
+         "  .short 5                      # Header: version" \
+         "  .short 0                      # Header: padding" \
+         "  .long 1                       # Header: compilation unit count" \
+         "  .long 0                       # Header: local type unit count" \
+         "  .long 0                       # Header: foreign type unit count" \
+         "  .long 2                       # Header: bucket count" \
+         "  .long 2                       # Header: name count" \
+         "  .long .Lnames_abbrev_end0-.Lnames_abbrev_start0 " \
+         "                                # Header: abbreviation table size" \
+         "  .long 8                       # Header: augmentation string size" \
+         "  .ascii \"LLVM0700\"    # Header: augmentation string" \
+         "  .long .Lcu1_begin             # Compilation unit 0" \
+         "  .long 1                       # Bucket 0" \
+         "  .long 0                       # Bucket 1" \
+         "  .long 193495088               # Hash in Bucket 0" \
+         "  .long 2090499946              # Hash in Bucket 0" \
+         "  .long $int_str_label          # String in Bucket 0: int" \
+         "  .long $main_str_label         # String in Bucket 0: main" \
+         "  .long .Lnames1-.Lnames_entries0 # Offset in Bucket 0" \
+         "  .long .Lnames0-.Lnames_entries0 # Offset in Bucket 0" \
+         ".Lnames_abbrev_start0:" \
+         "  .byte 46                      # Abbrev code" \
+         "  .byte 46                      # DW_TAG_subprogram" \
+         "  .byte 3                       # DW_IDX_die_offset" \
+         "  .byte 19                      # DW_FORM_ref4" \
+         "  .byte 0                       # End of abbrev" \
+         "  .byte 0                       # End of abbrev" \
+         "  .byte 36                      # Abbrev code" \
+         "  .byte 36                      # DW_TAG_base_type" \
+         "  .byte 3                       # DW_IDX_die_offset" \
+         "  .byte 19                      # DW_FORM_ref4" \
+         "  .byte 0                       # End of abbrev" \
+         "  .byte 0                       # End of abbrev" \
+         "  .byte 0                       # End of abbrev list" \
+         ".Lnames_abbrev_end0:" \
+         ".Lnames_entries0:" \
+         ".Lnames1:" \
+         "  .byte 36                      # Abbreviation code" \
+         "  .long $int_die_label - .Lcu1_begin # DW_IDX_die_offset" \
+         "  .long 0                       # End of list: int" \
+         ".Lnames0:" \
+         "  .byte 46                      # Abbreviation code" \
+         "  .long $main_die_label - .Lcu1_begin # DW_IDX_die_offset" \
+         "  .long 0                       # End of list: main" \
+         "  .p2align 2" \
+         ".Ldebug_names_end:"]
+
+set asm_file [standard_output_file $srcfile2]
+Dwarf::assemble $asm_file {
+    global srcdir subdir srcfile
+
+    lassign [function_range main ${srcdir}/${subdir}/${srcfile}] \
+	main_start main_length
+
+    cu {} {
+	DW_TAG_compile_unit {
+                {DW_AT_language @DW_LANG_C}
+                {DW_AT_name     clang-debug-names.c}
+                {DW_AT_comp_dir /tmp}
+
+        } {
+	    global int_die_label
+	    global main_die_label
+
+	    define_label $int_die_label
+	    base_type {
+		{name "int"}
+		{encoding @DW_ATE_signed}
+		{byte_size 4 DW_FORM_sdata}
+	    }
+
+	    define_label $main_die_label
+	    subprogram {
+		{name main}
+		{type :$int_die_label}
+		{low_pc $main_start addr}
+		{high_pc "$main_start + $main_length" addr}
+	    }
+	}
+    }
+
+    _defer_output .debug_str {
+	global debug_str
+	_emit [join $debug_str "\n"]
+    }
+
+    _defer_output .debug_names {
+	global debug_names
+	_emit [join $debug_names "\n"]
+    }
+}
+
+if { [prepare_for_testing "failed to prepare" ${testfile} \
+	  [list $srcfile $asm_file] {nodebug}] } {
+    return -1
+}
+
+set cmd "ptype main"
+set pass_re \
+    [multi_line \
+	 $cmd \
+	 "type = int \\(\\)"]
+set kfail_re \
+    [multi_line \
+	 $cmd \
+	 "type = <unknown return type> \\(\\)"]
+gdb_test_multiple $cmd "" {
+    -re -wrap $pass_re {
+	pass $gdb_test_name
+    }
+    -re -wrap $kfail_re {
+	kfail symtab/25952 $gdb_test_name
+    }
+}