Use counted_command_line everywhere

Currently command lines are reference counted using shared_ptr only
when attached to breakpoints.  This patch changes gdb to use
shared_ptr in commands as well.  This allows for the removal of
copy_command_lines.

Note that the change to execute_user_command explicitly makes a new
reference to the command line.  This will be used in a later patch.

This simplifies struct command_line based on the observation that a
given command can have at most two child bodies: an "if" can have both
"then" and "else" parts.  Perhaps the names I've chosen for the
replacements here are not very good -- your input requested.

ChangeLog
2018-05-04  Tom Tromey  <tom@tromey.com>

	* tracepoint.c (all_tracepoint_actions): Rename from
	all_tracepoint_actions_and_cleanup.  Change return type.
	(actions_command, encode_actions_1, encode_actions)
	(trace_dump_actions, tdump_command): Update.
	* remote.c (remote_download_command_source): Update.
	* python/python.c (gdbpy_eval_from_control_command)
	(python_command, python_interactive_command): Update.
	* mi/mi-cmd-break.c (mi_cmd_break_commands): Update.
	* guile/guile.c (guile_command)
	(gdbscm_eval_from_control_command, guile_command): Update.
	* compile/compile.c (compile_code_command)
	(compile_print_command, compile_to_object): Update.
	* cli/cli-script.h (struct command_lines_deleter): New.
	(counted_command_line): New typedef.
	(struct command_line): Add constructor, destructor.
	<body_list>: Remove.
	<body_list_0, body_list_1>: New members.
	(command_line_up): Remove typedef.
	(read_command_lines, read_command_lines_1, get_command_line):
	Update.
	(copy_command_lines): Don't declare.
	* cli/cli-script.c (build_command_line): Use "new".
	(get_command_line): Return counted_command_line.
	(print_command_lines, execute_user_command)
	(execute_control_command_1, while_command, if_command): Update.
	(realloc_body_list): Remove.
	(process_next_line, recurse_read_control_structure): Update.
	(read_command_lines, read_command_lines_1): Return counted_command_line.
	(free_command_lines): Use "delete".
	(copy_command_lines): Remove.
	(define_command, document_command, show_user_1): Update.
	* cli/cli-decode.h (struct cmd_list_element) <user_commands>: Now
	a counted_command_line.
	* breakpoint.h (counted_command_line): Remove typedef.
	(breakpoint_set_commands): Update.
	* breakpoint.c (check_no_tracepoint_commands)
	(validate_commands_for_breakpoint): Update.
	(breakpoint_set_commands): Change commands to be a
	counted_command_line.
	(commands_command_1, update_dprintf_command_list)
	(create_tracepoint_from_upload): Update.

gdb/cli/cli-script.h

@@ -45,31 +45,7 @@ enum command_control_type
   invalid_control
 };
 
-/* * Structure for saved commands lines (for breakpoints, defined
-   commands, etc).  */
-
-struct command_line
-{
-  struct command_line *next;
-  char *line;
-  enum command_control_type control_type;
-  union
-    {
-      struct
-	{
-	  enum compile_i_scope_types scope;
-	  void *scope_data;
-	}
-      compile;
-    }
-  control_u;
-  /* * The number of elements in body_list.  */
-  int body_count;
-  /* * For composite commands, the nested lists of commands.  For
-     example, for "if" command this will contain the then branch and
-     the else branch, if that is available.  */
-  struct command_line **body_list;
-};
+struct command_line;
 
 extern void free_command_lines (struct command_line **);
 
@@ -83,16 +59,58 @@ struct command_lines_deleter
   }
 };
 
-/* A unique pointer to a command_line.  */
+/* A reference-counted struct command_line.  */
+typedef std::shared_ptr<command_line> counted_command_line;
 
-typedef std::unique_ptr<command_line, command_lines_deleter> command_line_up;
+/* * Structure for saved commands lines (for breakpoints, defined
+   commands, etc).  */
 
-extern command_line_up read_command_lines (char *, int, int,
-					   void (*)(char *, void *),
-					   void *);
-extern command_line_up read_command_lines_1 (char * (*) (void), int,
-					     void (*)(char *, void *),
-					     void *);
+struct command_line
+{
+  explicit command_line (command_control_type type_, char *line_ = nullptr)
+    : line (line_),
+      control_type (type_)
+  {
+    memset (&control_u, 0, sizeof (control_u));
+  }
+
+  DISABLE_COPY_AND_ASSIGN (command_line);
+
+  struct command_line *next = nullptr;
+  char *line;
+  enum command_control_type control_type;
+  union
+    {
+      struct
+	{
+	  enum compile_i_scope_types scope;
+	  void *scope_data;
+	}
+      compile;
+    }
+  control_u;
+  /* * For composite commands, the nested lists of commands.  For
+     example, for "if" command this will contain the then branch and
+     the else branch, if that is available.  */
+  counted_command_line body_list_0;
+  counted_command_line body_list_1;
+
+private:
+
+  friend void free_command_lines (struct command_line **);
+
+  ~command_line ()
+  {
+    xfree (line);
+  }
+};
+
+extern counted_command_line read_command_lines (char *, int, int,
+						void (*)(char *, void *),
+						void *);
+extern counted_command_line read_command_lines_1 (char * (*) (void), int,
+						  void (*)(char *, void *),
+						  void *);
 
 
 /* Exported to cli/cli-cmds.c */
@@ -112,14 +130,12 @@ extern enum command_control_type
 extern enum command_control_type
 	execute_control_command_untraced (struct command_line *cmd);
 
-extern command_line_up get_command_line (enum command_control_type,
-					 const char *);
+extern counted_command_line get_command_line (enum command_control_type,
+					      const char *);
 
 extern void print_command_lines (struct ui_out *,
 				 struct command_line *, unsigned int);
 
-extern command_line_up copy_command_lines (struct command_line *cmds);
-
 /* Exported to gdb/infrun.c */
 
 extern void execute_user_command (struct cmd_list_element *c, const char *args);