Add expected type parameter to evaluate_expression

While working on the expression rewrite, I found a few spots that
called the internal functions of the expression evaluator, just to
pass in an expected type.  This patch adds a parameter to
evaluate_expression so that these functions can avoid this dependency.

Regression tested on x86-64 Fedora 28.

gdb/ChangeLog
2020-12-15  Tom Tromey  <tom@tromey.com>

	* stap-probe.c (stap_probe::evaluate_argument): Use
	evaluate_expression.
	* dtrace-probe.c (dtrace_probe::evaluate_argument): Use
	evaluate_expression.
	* value.h (evaluate_expression): Add expect_type parameter.
	* objc-lang.c (print_object_command): Call evaluate_expression.
	* eval.c (evaluate_expression): Add expect_type parameter.

gdb/ChangeLog

@@ -1,3 +1,13 @@
+2020-12-15  Tom Tromey  <tom@tromey.com>
+
+	* stap-probe.c (stap_probe::evaluate_argument): Use
+	evaluate_expression.
+	* dtrace-probe.c (dtrace_probe::evaluate_argument): Use
+	evaluate_expression.
+	* value.h (evaluate_expression): Add expect_type parameter.
+	* objc-lang.c (print_object_command): Call evaluate_expression.
+	* eval.c (evaluate_expression): Add expect_type parameter.
+
 2020-12-15  Tom Tromey  <tom@tromey.com>
 
 	* varobj.c (varobj_create): Use first_opcode.

gdb/dtrace-probe.c

@@ -714,11 +714,9 @@ dtrace_probe::evaluate_argument (unsigned n,
 {
   struct gdbarch *gdbarch = this->get_gdbarch ();
   struct dtrace_probe_arg *arg;
-  int pos = 0;
 
   arg = this->get_arg_by_number (n, gdbarch);
-  return evaluate_subexp_standard (arg->type, arg->expr.get (), &pos,
-				   EVAL_NORMAL);
+  return evaluate_expression (arg->expr.get (), arg->type);
 }
 
 /* Implementation of the compile_to_ax method.  */

gdb/eval.c

@@ -120,17 +120,15 @@ parse_to_comma_and_eval (const char **expp)
   return evaluate_expression (expr.get ());
 }
 
-/* Evaluate an expression in internal prefix form
-   such as is constructed by parse.y.
 
-   See expression.h for info on the format of an expression.  */
+/* See value.h.  */
 
 struct value *
-evaluate_expression (struct expression *exp)
+evaluate_expression (struct expression *exp, struct type *expect_type)
 {
   int pc = 0;
 
-  return evaluate_subexp (nullptr, exp, &pc, EVAL_NORMAL);
+  return evaluate_subexp (expect_type, exp, &pc, EVAL_NORMAL);
 }
 
 /* Evaluate an expression, avoiding all memory references

gdb/objc-lang.c

@@ -1194,10 +1194,10 @@ print_object_command (const char *args, int from_tty)
 
   {
     expression_up expr = parse_expression (args);
-    int pc = 0;
 
-    object = evaluate_subexp (builtin_type (expr->gdbarch)->builtin_data_ptr,
-			      expr.get (), &pc, EVAL_NORMAL);
+    object
+      = evaluate_expression (expr.get (),
+			     builtin_type (expr->gdbarch)->builtin_data_ptr);
   }
 
   /* Validate the address for sanity.  */

gdb/stap-probe.c

@@ -1389,12 +1389,10 @@ struct value *
 stap_probe::evaluate_argument (unsigned n, struct frame_info *frame)
 {
   struct stap_probe_arg *arg;
-  int pos = 0;
   struct gdbarch *gdbarch = get_frame_arch (frame);
 
   arg = this->get_arg_by_number (n, gdbarch);
-  return evaluate_subexp_standard (arg->atype, arg->aexpr.get (), &pos,
-				   EVAL_NORMAL);
+  return evaluate_expression (arg->aexpr.get (), arg->atype);
 }
 
 /* Compile the probe's argument N (indexed from 0) to agent expression.

gdb/value.h

@@ -905,7 +905,14 @@ extern int using_struct_return (struct gdbarch *gdbarch,
 				struct value *function,
 				struct type *value_type);
 
-extern struct value *evaluate_expression (struct expression *exp);
+/* Evaluate the expression EXP.  If set, EXPECT_TYPE is passed to the
+   outermost operation's evaluation.  This is ignored by most
+   operations, but may be used, e.g., to determine the type of an
+   otherwise untyped symbol.  The caller should not assume that the
+   returned value has this type.  */
+
+extern struct value *evaluate_expression (struct expression *exp,
+					  struct type *expect_type = nullptr);
 
 extern struct value *evaluate_type (struct expression *exp);