Introduce scope_operation

This adds class scope_operation, an implementation of OP_SCOPE.

gdb/ChangeLog
2021-03-08  Tom Tromey  <tom@tromey.com>

	* expop.h (class scope_operation): New.
	* eval.c (eval_op_scope): No longer static.
	(scope_operation::evaluate_for_address): New method.
	* ax-gdb.c (scope_operation::do_generate_ax): New method.

gdb/ChangeLog

@@ -1,3 +1,10 @@
+2021-03-08  Tom Tromey  <tom@tromey.com>
+
+	* expop.h (class scope_operation): New.
+	* eval.c (eval_op_scope): No longer static.
+	(scope_operation::evaluate_for_address): New method.
+	* ax-gdb.c (scope_operation::do_generate_ax): New method.
+
 2021-03-08  Tom Tromey  <tom@tromey.com>
 
 	* expprint.c (float_const_operation::dump): New method.

gdb/ax-gdb.c

@@ -2301,6 +2301,19 @@ operation::generate_ax (struct expression *exp,
     }
 }
 
+void
+scope_operation::do_generate_ax (struct expression *exp,
+				 struct agent_expr *ax,
+				 struct axs_value *value,
+				 struct type *cast_type)
+{
+  struct type *type = std::get<0> (m_storage);
+  const std::string &name = std::get<1> (m_storage);
+  int found = gen_aggregate_elt_ref (ax, value, type, name.c_str ());
+  if (!found)
+    error (_("There is no field named %s"), name.c_str ());
+}
+
 }
 
 /* This handles the middle-to-right-side of code generation for binary

gdb/eval.c

@@ -1185,7 +1185,7 @@ is_integral_or_integral_reference (struct type *type)
 
 /* Helper function that implements the body of OP_SCOPE.  */
 
-static struct value *
+struct value *
 eval_op_scope (struct type *expect_type, struct expression *exp,
 	       enum noside noside,
 	       struct type *type, const char *string)
@@ -3289,6 +3289,18 @@ operation::evaluate_for_address (struct expression *exp, enum noside noside)
   return evaluate_subexp_for_address_base (exp, noside, val);
 }
 
+value *
+scope_operation::evaluate_for_address (struct expression *exp,
+				       enum noside noside)
+{
+  value *x = value_aggregate_elt (std::get<0> (m_storage),
+				  std::get<1> (m_storage).c_str (),
+				  NULL, 1, noside);
+  if (x == NULL)
+    error (_("There is no field named %s"), std::get<1> (m_storage).c_str ());
+  return x;
+}
+
 }
 
 /* Evaluate like `evaluate_subexp' except coercing arrays to pointers.

gdb/expop.h

@@ -41,6 +41,11 @@ extern void gen_expr_structop (struct expression *exp,
 			       const char *name,
 			       struct agent_expr *ax, struct axs_value *value);
 
+extern struct value *eval_op_scope (struct type *expect_type,
+				    struct expression *exp,
+				    enum noside noside,
+				    struct type *type, const char *string);
+
 namespace expr
 {
 
@@ -415,6 +420,37 @@ private:
   float_data m_data;
 };
 
+class scope_operation
+  : public maybe_constant_operation<struct type *, std::string>
+{
+public:
+
+  using maybe_constant_operation::maybe_constant_operation;
+
+  value *evaluate (struct type *expect_type,
+		   struct expression *exp,
+		   enum noside noside) override
+  {
+    return eval_op_scope (expect_type, exp, noside,
+			  std::get<0> (m_storage),
+			  std::get<1> (m_storage).c_str ());
+  }
+
+  value *evaluate_for_address (struct expression *exp,
+			       enum noside noside) override;
+
+  enum exp_opcode opcode () const override
+  { return OP_SCOPE; }
+
+protected:
+
+  void do_generate_ax (struct expression *exp,
+		       struct agent_expr *ax,
+		       struct axs_value *value,
+		       struct type *cast_type)
+    override;
+};
+
 } /* namespace expr */
 
 #endif /* EXPOP_H */