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.

1 files changed, 23 insertions, 0 deletions

diff --git a/gdb/testsuite/gdb.ada/voidctx/pck.ads b/gdb/testsuite/gdb.ada/voidctx/pck.ads
new file mode 100644
index 0000000..cf7fe15
--- /dev/null
+++ b/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;