[RFA 7/7] Use ui_out_emit_list and ui_out_emit_tuple with gdb::optional

[Tom Tromey <tom at tromey dot com>]

This changes a few spots to use ui_out_emit_list and/or
ui_out_emit_tuple with gdb::optional, to preserve existing behavior.
This allows for the removal of a few more cleanups.

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

	* mi/mi-cmd-var.c (mi_cmd_var_list_children): Use gdb::optional,
	ui_out_emit_list, ui_out_emit_tuple.
	(mi_cmd_var_update): Likewise.
---
 gdb/ChangeLog       |  6 ++++++
 gdb/mi/mi-cmd-var.c | 24 +++++++++++++-----------
 2 files changed, 19 insertions(+), 11 deletions(-)

diff --git a/gdb/ChangeLog b/gdb/ChangeLog
index cc8e4e4..d1ed50f 100644
--- a/gdb/ChangeLog
+++ b/gdb/ChangeLog
@@ -1,5 +1,11 @@
 2017-09-09  Tom Tromey  <tom@tromey.com>
 
+	* mi/mi-cmd-var.c (mi_cmd_var_list_children): Use gdb::optional,
+	ui_out_emit_list, ui_out_emit_tuple.
+	(mi_cmd_var_update): Likewise.
+
+2017-09-09  Tom Tromey  <tom@tromey.com>
+
 	* mi/mi-interp.c (mi_user_selected_context_changed): Use
 	ui_out_redirect_pop.
 	* guile/scm-ports.c (ioscm_with_output_to_port_worker): Use
diff --git a/gdb/mi/mi-cmd-var.c b/gdb/mi/mi-cmd-var.c
index 191e770..8b22b2f 100644
--- a/gdb/mi/mi-cmd-var.c
+++ b/gdb/mi/mi-cmd-var.c
@@ -410,14 +410,15 @@ mi_cmd_var_list_children (const char *command, char **argv, int argc)
 
   if (from < to)
     {
-      struct cleanup *cleanup_children;
+      /* For historical reasons this might emit a list or a tuple, so
+	 we construct one or the other.  */
+      gdb::optional<ui_out_emit_tuple> tuple_emitter;
+      gdb::optional<ui_out_emit_list> list_emitter;
 
       if (mi_version (uiout) == 1)
-	cleanup_children
-	  = make_cleanup_ui_out_tuple_begin_end (uiout, "children");
+	tuple_emitter.emplace (uiout, "children");
       else
-	cleanup_children
-	  = make_cleanup_ui_out_list_begin_end (uiout, "children");
+	list_emitter.emplace (uiout, "children");
       for (ix = from;
 	   ix < to && VEC_iterate (varobj_p, children, ix, child);
 	   ++ix)
@@ -426,7 +427,6 @@ mi_cmd_var_list_children (const char *command, char **argv, int argc)
 
 	  print_varobj (child, print_values, 1 /* print expression */);
 	}
-      do_cleanups (cleanup_children);
     }
 
   uiout->field_int ("has_more", varobj_has_more (var, to));
@@ -648,7 +648,6 @@ void
 mi_cmd_var_update (const char *command, char **argv, int argc)
 {
   struct ui_out *uiout = current_uiout;
-  struct cleanup *cleanup;
   char *name;
   enum print_values print_values;
 
@@ -665,10 +664,15 @@ mi_cmd_var_update (const char *command, char **argv, int argc)
   else
     print_values = PRINT_NO_VALUES;
 
+  /* For historical reasons this might emit a list or a tuple, so we
+     construct one or the other.  */
+  gdb::optional<ui_out_emit_tuple> tuple_emitter;
+  gdb::optional<ui_out_emit_list> list_emitter;
+
   if (mi_version (uiout) <= 1)
-    cleanup = make_cleanup_ui_out_tuple_begin_end (uiout, "changelist");
+    tuple_emitter.emplace (uiout, "changelist");
   else
-    cleanup = make_cleanup_ui_out_list_begin_end (uiout, "changelist");
+    list_emitter.emplace (uiout, "changelist");
 
   /* Check if the parameter is a "*", which means that we want to
      update all variables.  */
@@ -693,8 +697,6 @@ mi_cmd_var_update (const char *command, char **argv, int argc)
 
       varobj_update_one (var, print_values, 1 /* explicit */);
     }
-
-  do_cleanups (cleanup);
 }
 
 /* Helper for mi_cmd_var_update().  */
-- 
2.9.4