Select variant field when printing variant

When I updated the Ada variant-printing code to be value-based, I
neglected a couple of issues.  First, print_variant_part must first
extract the variant field before finding the active component; second,
print_field_values should pass in the field value as the outer value
when recursing.

This patch fixes both of these issues.

gdb/ChangeLog
2020-04-06  Tom Tromey  <tromey@adacore.com>

	* ada-valprint.c (print_variant_part): Extract the variant field.
	(print_field_values): Use the field as the outer value when
	recursing.

gdb/testsuite/ChangeLog
2020-04-06  Tom Tromey  <tromey@adacore.com>

	* gdb.ada/variant-record/proc.adb: New file.
	* gdb.ada/variant-record/value.adb: New file.
	* gdb.ada/variant-record/value.s: New file.
	* gdb.ada/variant-record.exp: New file.

gdb/ChangeLog

@@ -1,3 +1,9 @@
+2020-04-06  Tom Tromey  <tromey@adacore.com>
+
+	* ada-valprint.c (print_variant_part): Extract the variant field.
+	(print_field_values): Use the field as the outer value when
+	recursing.
+
 2020-04-06  Tom Tromey  <tromey@adacore.com>
 
 	* sh-nbsd-tdep.c: Include nbsd-tdep.h.

gdb/ada-valprint.c

@@ -565,7 +565,8 @@ print_variant_part (struct value *value, int field_num,
   if (which < 0)
     return 0;
 
-  struct value *active_component = value_field (value, which);
+  struct value *variant_field = value_field (value, field_num);
+  struct value *active_component = value_field (variant_field, which);
   return print_field_values (active_component, outer_value, stream, recurse,
 			     options, comma_needed, language);
 }
@@ -603,8 +604,9 @@ print_field_values (struct value *value, struct value *outer_value,
 
       if (ada_is_wrapper_field (type, i))
 	{
+	  struct value *field_val = value_field (value, i);
 	  comma_needed =
-	    print_field_values (value_field (value, i), outer_value,
+	    print_field_values (field_val, field_val,
 				stream, recurse, options,
 				comma_needed, language);
 	  continue;

gdb/testsuite/ChangeLog

@@ -1,3 +1,10 @@
+2020-04-06  Tom Tromey  <tromey@adacore.com>
+
+	* gdb.ada/variant-record/proc.adb: New file.
+	* gdb.ada/variant-record/value.adb: New file.
+	* gdb.ada/variant-record/value.s: New file.
+	* gdb.ada/variant-record.exp: New file.
+
 2020-04-03  Hannes Domani  <ssbssa@yahoo.de>
 
 	PR gdb/25325

gdb/testsuite/gdb.ada/variant-record.exp

@@ -0,0 +1,30 @@
+# 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 "ada.exp"
+
+standard_ada_testfile proc
+
+if {[gdb_compile_ada "${srcfile}" "${binfile}" executable debug] != ""} {
+  return -1
+}
+
+clean_restart ${testfile}
+
+set bp_location [gdb_get_line_number "STOP" ${testdir}/proc.adb]
+runto "proc.adb:$bp_location"
+
+gdb_test "print Value.Name(My_Value)" \
+    "= \\(well => yes, name => \"abcdefgh\"\\)"

gdb/testsuite/gdb.ada/variant-record/proc.adb

@@ -0,0 +1,21 @@
+--  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/>.
+
+with Value;
+procedure Proc is
+  My_Value : Value.T := Value.Create;
+begin
+  null; -- STOP
+end;

gdb/testsuite/gdb.ada/variant-record/value.adb

@@ -0,0 +1,30 @@
+--  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/>.
+
+package body Value is
+  function Create return T is
+  begin
+    return (One => (Well => Value_Name.No,
+                    Unique_Name => (X1 => 1, X2 => 2)),
+            Two => (Well => Value_Name.Yes,
+                    Name => "abcdefgh"));
+  end Create;
+
+  function Name (Of_Value : T) return Value_Name.T is
+  begin
+    return Of_Value.Two;
+  end Name;
+
+end Value;

gdb/testsuite/gdb.ada/variant-record/value.ads

@@ -0,0 +1,48 @@
+--  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/>.
+
+package Value is
+  package Value_Name is
+    Length : constant Positive := 8;
+    subtype Name_T is String (1 .. Length);
+
+    type A_Record_T is
+      record
+        X1 : Natural;
+        X2 : Natural;
+      end record;
+
+    type Yes_No_T is (Yes, No);
+    type T (Well : Yes_No_T := Yes) is
+      record
+        case Well is
+          when Yes =>
+            Name : Name_T;
+          when No =>
+            Unique_Name : A_Record_T;
+        end case;
+      end record;
+  end;
+
+  type T is private;
+  function Create return T;
+  function Name (Of_Value : T) return Value_Name.T;
+private
+  type T is
+    record
+      One : Value_Name.T (Well => Value_Name.No);
+      Two : Value_Name.T (Well => Value_Name.Yes);
+    end record;
+end;