Remove cleanups from prepare_execute_command

This changes prepare_execute_command to return a scoped_value_mark
rather than a cleanup.

ChangeLog
2017-10-19  Tom Tromey  <tom@tromey.com>

	* mi/mi-main.c (mi_cmd_execute): Update.
	* top.h (prepare_execute_command): Return scoped_value_mark.
	* value.h (class scoped_value_mark): Use DISABLE_COPY_AND_ASSIGN.
	Add move constructor.
	* top.c (prepare_execute_command): Return scoped_value_mark.
	(execute_command): Update.

gdb/ChangeLog

@@ -1,3 +1,12 @@
+2017-10-19  Tom Tromey  <tom@tromey.com>
+
+	* mi/mi-main.c (mi_cmd_execute): Update.
+	* top.h (prepare_execute_command): Return scoped_value_mark.
+	* value.h (class scoped_value_mark): Use DISABLE_COPY_AND_ASSIGN.
+	Add move constructor.
+	* top.c (prepare_execute_command): Return scoped_value_mark.
+	(execute_command): Update.
+
 2017-10-19  Pedro Alves  <palves@redhat.com>
 
 	* xml-support.c (xml_fetch_content_from_file): Check fread's

gdb/mi/mi-main.c

@@ -2095,9 +2095,7 @@ mi_execute_command (const char *cmd, int from_tty)
 static void
 mi_cmd_execute (struct mi_parse *parse)
 {
-  struct cleanup *cleanup;
-
-  cleanup = prepare_execute_command ();
+  scoped_value_mark cleanup = prepare_execute_command ();
 
   if (parse->all && parse->thread_group != -1)
     error (_("Cannot specify --thread-group together with --all"));
@@ -2189,7 +2187,6 @@ mi_cmd_execute (struct mi_parse *parse)
 
       error_stream (stb);
     }
-  do_cleanups (cleanup);
 }
 
 /* FIXME: This is just a hack so we can get some extra commands going.

gdb/top.c

@@ -438,15 +438,9 @@ do_chdir_cleanup (void *old_dir)
 }
 #endif
 
-struct cleanup *
-prepare_execute_command (void)
+scoped_value_mark
+prepare_execute_command ()
 {
-  struct value *mark;
-  struct cleanup *cleanup;
-
-  mark = value_mark ();
-  cleanup = make_cleanup_value_free_to_mark (mark);
-
   /* With multiple threads running while the one we're examining is
      stopped, the dcache can get stale without us being able to detect
      it.  For the duration of the command, though, use the dcache to
@@ -454,7 +448,7 @@ prepare_execute_command (void)
   if (non_stop)
     target_dcache_invalidate ();
 
-  return cleanup;
+  return scoped_value_mark ();
 }
 
 /* Tell the user if the language has changed (except first time) after
@@ -534,12 +528,12 @@ maybe_wait_sync_command_done (int was_sync)
 void
 execute_command (char *p, int from_tty)
 {
-  struct cleanup *cleanup_if_error, *cleanup;
+  struct cleanup *cleanup_if_error;
   struct cmd_list_element *c;
   char *line;
 
   cleanup_if_error = make_bpstat_clear_actions_cleanup ();
-  cleanup = prepare_execute_command ();
+  scoped_value_mark cleanup = prepare_execute_command ();
 
   /* Force cleanup of any alloca areas if using C alloca instead of
      a builtin alloca.  */
@@ -548,7 +542,6 @@ execute_command (char *p, int from_tty)
   /* This can happen when command_line_input hits end of file.  */
   if (p == NULL)
     {
-      do_cleanups (cleanup);
       discard_cleanups (cleanup_if_error);
       return;
     }
@@ -623,7 +616,6 @@ execute_command (char *p, int from_tty)
 
   check_frame_language_change ();
 
-  do_cleanups (cleanup);
   discard_cleanups (cleanup_if_error);
 }
 

gdb/top.h

@@ -22,6 +22,7 @@
 
 #include "buffer.h"
 #include "event-loop.h"
+#include "value.h"
 
 struct tl_interp_info;
 
@@ -249,7 +250,7 @@ extern void check_frame_language_change (void);
 /* Prepare for execution of a command.
    Call this before every command, CLI or MI.
    Returns a cleanup to be run after the command is completed.  */
-extern struct cleanup *prepare_execute_command (void);
+extern scoped_value_mark prepare_execute_command (void);
 
 /* This function returns a pointer to the string that is used
    by gdb for its command prompt.  */

gdb/value.h

@@ -730,6 +730,10 @@ class scoped_value_mark
     free_to_mark ();
   }
 
+  scoped_value_mark (scoped_value_mark &&other) = default;
+
+  DISABLE_COPY_AND_ASSIGN (scoped_value_mark);
+
   /* Free the values currently on the value stack.  */
   void free_to_mark ()
   {