Pass void_context_p to parse_expression

An earlier patch pointed out that nothing in GDB sets void_context_p
when parsing an expression.  This patch fixes this omission.

"print" and "call" differ in that the former will print a value that
has void type, while the latter will not.  AdaCore has had a patch for
a long time that uses this distinction to help with overload
resolution.  In particular, in a "call" context, a procedure will be
chosen, while in a "print" context, a zero-argument function will be
chosen instead.

Regression tested on x86-64 Fedora 32.

gdb/ChangeLog
2021-01-08  Tom Tromey  <tromey@adacore.com>

	* parse.c (parse_expression): Add void_context_p parameter.  Use
	parse_exp_in_context.
	* printcmd.c (print_command_1): Change voidprint to bool.  Pass to
	parse_expression.
	(print_command, call_command): Update.
	* expression.h (parse_expression): Add void_context_p parameter.

gdb/testsuite/ChangeLog
2021-01-08  Tom Tromey  <tromey@adacore.com>

	* gdb.ada/voidctx/pck.adb: New file.
	* gdb.ada/voidctx/pck.ads: New file.
	* gdb.ada/voidctx/voidctx.adb: New file.
	* gdb.ada/voidctx.exp: New file.

gdb/ChangeLog

@@ -1,3 +1,12 @@
+2021-01-08  Tom Tromey  <tromey@adacore.com>
+
+	* parse.c (parse_expression): Add void_context_p parameter.  Use
+	parse_exp_in_context.
+	* printcmd.c (print_command_1): Change voidprint to bool.  Pass to
+	parse_expression.
+	(print_command, call_command): Update.
+	* expression.h (parse_expression): Add void_context_p parameter.
+
 2021-01-08  Andrew Burgess  <andrew.burgess@embecosm.com>
 
 	* value.c (set_value_component_location): Adjust the VALUE_LVAL

gdb/expression.h

@@ -142,7 +142,8 @@ typedef std::unique_ptr<expression> expression_up;
 
 class innermost_block_tracker;
 extern expression_up parse_expression (const char *,
-				       innermost_block_tracker * = nullptr);
+				       innermost_block_tracker * = nullptr,
+				       bool void_context_p = false);
 
 extern expression_up parse_expression_with_language (const char *string,
 						     enum language lang);

gdb/parse.c

@@ -1158,13 +1158,20 @@ parse_exp_in_context (const char **stringptr, CORE_ADDR pc,
   return result;
 }
 
-/* Parse STRING as an expression, and complain if this fails
-   to use up all of the contents of STRING.  */
+/* Parse STRING as an expression, and complain if this fails to use up
+   all of the contents of STRING.  TRACKER, if non-null, will be
+   updated by the parser.  VOID_CONTEXT_P should be true to indicate
+   that the expression may be expected to return a value with void
+   type.  Parsers are free to ignore this, or to use it to help with
+   overload resolution decisions.  */
 
 expression_up
-parse_expression (const char *string, innermost_block_tracker *tracker)
+parse_expression (const char *string, innermost_block_tracker *tracker,
+		  bool void_context_p)
 {
-  expression_up exp = parse_exp_1 (&string, 0, 0, 0, tracker);
+  expression_up exp = parse_exp_in_context (&string, 0, nullptr, 0,
+					    void_context_p, nullptr,
+					    tracker, nullptr);
   if (*string)
     error (_("Junk after end of expression."));
   return exp;

gdb/printcmd.c

@@ -1206,7 +1206,7 @@ print_value (value *val, const value_print_options &opts)
 /* Implementation of the "print" and "call" commands.  */
 
 static void
-print_command_1 (const char *args, int voidprint)
+print_command_1 (const char *args, bool voidprint)
 {
   struct value *val;
   value_print_options print_opts;
@@ -1223,7 +1223,9 @@ print_command_1 (const char *args, int voidprint)
 
   if (exp != nullptr && *exp)
     {
-      expression_up expr = parse_expression (exp);
+      /* VOIDPRINT is true to indicate that we do want to print a void
+	 value, so invert it for parse_expression.  */
+      expression_up expr = parse_expression (exp, nullptr, !voidprint);
       val = evaluate_expression (expr.get ());
     }
   else
@@ -1321,14 +1323,14 @@ print_command_completer (struct cmd_list_element *ignore,
 static void
 print_command (const char *exp, int from_tty)
 {
-  print_command_1 (exp, 1);
+  print_command_1 (exp, true);
 }
 
 /* Same as print, except it doesn't print void results.  */
 static void
 call_command (const char *exp, int from_tty)
 {
-  print_command_1 (exp, 0);
+  print_command_1 (exp, false);
 }
 
 /* Implementation of the "output" command.  */

gdb/testsuite/ChangeLog

@@ -1,3 +1,10 @@
+2021-01-08  Tom Tromey  <tromey@adacore.com>
+
+	* gdb.ada/voidctx/pck.adb: New file.
+	* gdb.ada/voidctx/pck.ads: New file.
+	* gdb.ada/voidctx/voidctx.adb: New file.
+	* gdb.ada/voidctx.exp: New file.
+
 2021-01-08  Simon Marchi  <simon.marchi@polymtl.ca>
 
 	PR gdb/27157

gdb/testsuite/gdb.ada/voidctx.exp

@@ -0,0 +1,40 @@
+# 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/>.
+
+load_lib "ada.exp"
+
+if { [skip_ada_tests] } { return -1 }
+
+standard_ada_testfile voidctx
+
+if {[gdb_compile_ada "${srcfile}" "${binfile}" executable [list debug ]] != "" } {
+  return -1
+}
+
+clean_restart ${testfile}
+
+set bp_location [gdb_get_line_number "STOP" ${testdir}/voidctx.adb]
+runto "voidctx.adb:$bp_location"
+
+gdb_test "print pck.proc_count" " = 0" "initial proc_count"
+gdb_test "print pck.func_count" " = 0" "initial func_count"
+
+gdb_test "print DoSomething" " = 42"
+gdb_test "print pck.proc_count" " = 0" "check proc_count 1"
+gdb_test "print pck.func_count" " = 1" "check func_count 1"
+
+gdb_test_no_output "call DoSomething"
+gdb_test "print pck.proc_count" " = 1" "check proc_count 2"
+gdb_test "print pck.func_count" " = 1" "check func_count 2"

gdb/testsuite/gdb.ada/voidctx/pck.adb

@@ -0,0 +1,27 @@
+--  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/>.
+
+package body Pck is
+   function DoSomething return Integer is
+   begin
+      Func_Count := Func_Count + 1;
+      return 42;
+   end;
+
+   procedure DoSomething is
+   begin
+      Proc_Count := Proc_Count + 1;
+   end;
+end Pck;

gdb/testsuite/gdb.ada/voidctx/pck.ads

@@ -0,0 +1,23 @@
+--  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/>.
+
+package Pck is
+   -- Each count is incremented by the respective DoSomething.
+   Proc_Count : Integer := 0;
+   Func_Count : Integer := 0;
+
+   function DoSomething return Integer;
+   procedure DoSomething;
+end Pck;

gdb/testsuite/gdb.ada/voidctx/voidctx.adb

@@ -0,0 +1,31 @@
+--  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/>.
+
+with Pck; use Pck;
+procedure Voidctx is
+
+   function DoSomething return Integer is
+   begin
+      return 42;
+   end;
+
+   procedure DoSomething is
+   begin
+      null;
+   end;
+
+begin
+   null;  -- STOP
+end Voidctx;