gdb/testsuite: use the correct .debug_str section name for DW_FORM_strp

When handling DWARF attributes of the form DW_FORM_strp the strings
should be placed in the .debug_str section, not .debug_string as they
currently are by the DWARF assembler (in lib/dwarf.exp).

I've added a test.  This is as much to test the DWARF generator as it
is to test GDB as GCC makes frequent use of DW_FORM_strp so we can be
pretty sure this part of GDB is already well tested.

gdb/testsuite/ChangeLog:

	* gdb.dwarf2/dw2-using-debug-str.c: New file.
	* gdb.dwarf2/dw2-using-debug-str.exp: New file.
	* lib/dwarf.exp (Dwarf::DW_FORM_strp): Create .debug_str section,
	not .debug_string.

gdb/testsuite/ChangeLog

@@ -1,3 +1,10 @@
+2021-03-22  Andrew Burgess  <andrew.burgess@embecosm.com>
+
+	* gdb.dwarf2/dw2-using-debug-str.c: New file.
+	* gdb.dwarf2/dw2-using-debug-str.exp: New file.
+	* lib/dwarf.exp (Dwarf::DW_FORM_strp): Create .debug_str section,
+	not .debug_string.
+
 2021-03-20  Tom Tromey  <tom@tromey.com>
 
 	* gdb.base/maint.exp: Update "maint print statistics" output.

gdb/testsuite/gdb.dwarf2/dw2-using-debug-str.c

@@ -0,0 +1,28 @@
+/* This testcase is part of GDB, the GNU debugger.
+
+   Copyright 2021 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/>.  */
+
+/* Our fake object.  */
+int global_var[100];
+
+int
+main (int argc, char **argv)
+{
+  asm ("main_label: .globl main_label");
+
+  return 0;
+}

gdb/testsuite/gdb.dwarf2/dw2-using-debug-str.exp

@@ -0,0 +1,101 @@
+# Copyright 2021 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/>.
+
+# This test is as much about testing the lib/dwarf.exp DWARF generator
+# as it is about testing GDB.  At the time this test was written, this
+# was the only test that generated any DWARF using DW_FORM_strp.
+
+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 .c -dw.S
+
+if { [prepare_for_testing "failed to prepare" ${testfile} ${srcfile}] } {
+    return -1
+}
+
+set asm_file [standard_output_file $srcfile2]
+Dwarf::assemble $asm_file {
+    global srcfile
+
+    cu {} {
+	compile_unit {
+            {language @DW_LANG_C}
+            {name ${srcfile}}
+        } {
+	    declare_labels int4_type struct_type
+
+	    int4_type: DW_TAG_base_type {
+		{DW_AT_byte_size 4 DW_FORM_sdata}
+		{DW_AT_encoding  @DW_ATE_signed}
+		{DW_AT_name      integer}
+	    }
+
+	    struct_type: DW_TAG_structure_type {
+		{DW_AT_name "foo_t" DW_FORM_strp}
+		{DW_AT_byte_size 12 DW_FORM_sdata}
+	    } {
+		member {
+		    {name "aa" DW_FORM_strp}
+		    {type :$int4_type}
+		    {data_member_location 0 data1}
+		}
+		member {
+		    {name "bb" DW_FORM_strp}
+		    {type :$int4_type}
+		    {data_member_location 4 data1}
+		}
+		member {
+		    {name "cc" DW_FORM_strp}
+		    {type :$int4_type}
+		    {data_member_location 8 data1}
+		}
+	    }
+
+	    DW_TAG_variable {
+		{DW_AT_name global_var DW_FORM_strp}
+		{DW_AT_type :$struct_type}
+		{DW_AT_location {
+		    DW_OP_addr [gdb_target_symbol global_var]
+		} SPECIAL_expr}
+		{external 1 flag}
+	    }
+
+	    subprogram {
+		{external 1 flag}
+		{name main DW_FORM_strp}
+		{MACRO_AT_range {main}}
+	    }
+	}
+    }
+}
+
+if { [prepare_for_testing "failed to prepare" ${testfile} \
+	  [list $srcfile $asm_file] {nodebug}] } {
+    return -1
+}
+
+if ![runto_main] {
+    return -1
+}
+
+# Print the type of global_var.  This type information is entirely
+# fictional, it only exists in the DWARF, but it contains lots of nice
+# field names, all of which are stored in the .debug_str section.
+gdb_test "p global_var" " = \\{aa = 0, bb = 0, cc = 0\\}"

gdb/testsuite/lib/dwarf.exp

@@ -507,7 +507,7 @@ namespace eval Dwarf {
 
 		if {![info exists _strings($value)]} {
 		    set _strings($value) [new_label strp]
-		    _defer_output .debug_string {
+		    _defer_output .debug_str {
 			define_label $_strings($value)
 			_op .ascii [_quote $value]
 		    }