Use generic_printstr from ada_language::printstr

Currently, if you create a lazy string while in Ada language mode, the
string will be rendered strangely, like:

    "["d0"]["9f"]["d1"]["80"]["d0"]["b8"]...

This happens because ada_printstr does not really handle UTF-8
decoding.

This patch changes ada_language::printstr to use generic_printstr when
UTF-8 is used.

Note that this code could probably be improved some more -- the
current patch only addresses the narrow case of the Python API.  I've
filed a follow-up bug (PR ada/32413) for the remaining changes.

Approved-By: Andrew Burgess <aburgess@redhat.com>

gdb/ada-lang.c

@@ -13800,8 +13800,15 @@ public:
 		 const char *encoding, int force_ellipses,
 		 const struct value_print_options *options) const override
   {
-    ada_printstr (stream, elttype, string, length, encoding,
-		  force_ellipses, options);
+    /* ada_printstr doesn't handle UTF-8 too well, but we want this
+       for lazy-string printing.  Defer this case to the generic
+       code.  */
+    if (encoding != nullptr && strcasecmp (encoding, "UTF-8") == 0)
+      generic_printstr (stream, elttype, string, length, encoding,
+			force_ellipses, '"', 0, options);
+    else
+      ada_printstr (stream, elttype, string, length, encoding,
+		    force_ellipses, options);
   }
 
   /* See language.h.  */

gdb/testsuite/gdb.ada/lazy-string.exp

@@ -0,0 +1,43 @@
+# Copyright 2024 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 GDB's 'set print characters' setting works for Ada strings.
+
+load_lib "ada.exp"
+load_lib gdb-python.exp
+
+require allow_ada_tests allow_python_tests
+
+standard_ada_testfile main
+
+# Enable basic use of UTF-8.  LC_ALL gets reset for each testfile.
+setenv LC_ALL C.UTF-8
+
+if {[gdb_compile_ada "${srcfile}" "${binfile}" executable {debug}] != ""} {
+    return -1
+}
+
+clean_restart ${testfile}
+
+set bp_location [gdb_get_line_number "STOP" ${testdir}/main.adb]
+if ![runto "main.adb:$bp_location" ] then {
+  return -1
+}
+
+gdb_test_no_output "python arg = gdb.parse_and_eval('arg.all')"
+
+gdb_test "python print(str(arg.lazy_string(encoding='utf-8')))" \
+    "\"funçao\"" \
+    "print lazy string using utf-8"

gdb/testsuite/gdb.ada/lazy-string/main.adb

@@ -0,0 +1,25 @@
+--  Copyright 2024 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/>.
+
+procedure Main is
+
+   procedure Blah (Arg : String) is
+   begin
+     null; -- STOP
+   end;
+
+begin
+   Blah ("funçao");
+end Main;