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, 11 insertions, 4 deletions

diff --git a/gdb/parse.c b/gdb/parse.c
index 51e7d65..b3cd91d 100644
--- a/gdb/parse.c
+++ b/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;