Replace interp_set_temp with scoped_restore_interp

This removes interp_set_temp and an associated cleanup, in favor of a
new RAII class, scoped_restore_interp.

ChangeLog
2017-09-11  Tom Tromey  <tom@tromey.com>

	* cli/cli-script.c (restore_interp): Remove.
	(read_command_lines): Use scoped_restore_interp.
	* interps.c (scoped_restore_interp::set_temp): Rename from
	interp_set_temp.
	* interps.h (class scoped_restore_interp): New.
	(interp_set_temp): Remove.

gdb/ChangeLog

@@ -1,3 +1,12 @@
+2017-09-11  Tom Tromey  <tom@tromey.com>
+
+	* cli/cli-script.c (restore_interp): Remove.
+	(read_command_lines): Use scoped_restore_interp.
+	* interps.c (scoped_restore_interp::set_temp): Rename from
+	interp_set_temp.
+	* interps.h (class scoped_restore_interp): New.
+	(interp_set_temp): Remove.
+
 2017-09-11  Tom Tromey  <tom@tromey.com>
 
 	* mi/mi-cmd-catch.c (mi_cmd_catch_assert)

gdb/cli/cli-script.c

@@ -1158,12 +1158,6 @@ recurse_read_control_structure (char * (*read_next_line_func) (void),
   return ret;
 }
 
-static void
-restore_interp (void *arg)
-{
-  interp_set_temp (interp_name ((struct interp *)arg));
-}
-
 /* Read lines from the input stream and accumulate them in a chain of
    struct command_line's, which is then returned.  For input from a
    terminal, the special command "end" is used to mark the end of the
@@ -1203,12 +1197,10 @@ read_command_lines (char *prompt_arg, int from_tty, int parse_commands,
 				 validator, closure);
   else
     {
-      struct interp *old_interp = interp_set_temp (INTERP_CONSOLE);
+      scoped_restore_interp interp_restorer (INTERP_CONSOLE);
-      struct cleanup *old_chain = make_cleanup (restore_interp, old_interp);
 
       head = read_command_lines_1 (read_next_line, parse_commands,
 				   validator, closure);
-      do_cleanups (old_chain);
     }
 
   if (from_tty && input_interactive_p (current_ui)

gdb/interps.c

@@ -288,7 +288,7 @@ current_interp_set_logging (ui_file_up logfile,
 
 /* Temporarily overrides the current interpreter.  */
 struct interp *
-interp_set_temp (const char *name)
+scoped_restore_interp::set_interp (const char *name)
 {
   struct ui_interp_info *ui_interp = get_current_interp_info ();
   struct interp *interp = interp_lookup (current_ui, name);

gdb/interps.h

@@ -104,6 +104,32 @@ extern struct ui_out *interp_ui_out (struct interp *interp);
 extern const char *interp_name (struct interp *interp);
 extern struct interp *interp_set_temp (const char *name);
 
+/* Temporarily set the current interpreter, and reset it on
+   destruction.  */
+class scoped_restore_interp
+{
+public:
+
+  scoped_restore_interp (const char *name)
+    : m_interp (set_interp (name))
+  {
+  }
+
+  ~scoped_restore_interp ()
+  {
+    set_interp (interp_name (m_interp));
+  }
+
+  scoped_restore_interp (const scoped_restore_interp &) = delete;
+  scoped_restore_interp &operator= (const scoped_restore_interp &) = delete;
+
+private:
+
+  struct interp *set_interp (const char *name);
+
+  struct interp *m_interp;
+};
+
 extern int current_interp_named_p (const char *name);
 
 /* Call this function to give the current interpreter an opportunity