Introduce gdb_argv, a class wrapper for buildargv

This introduces gdb_argv, a class wrapping an "argv" pointer; that is,
a pointer to a NULL-terminated array of char*, where both the array
and each non-NULL element in the array are xmalloc'd.

This patch then changes most users of gdb_buildargv to use gdb_argv
instead.

ChangeLog
2017-08-03  Tom Tromey  <tom@tromey.com>

	* utils.h (struct gdb_argv_deleter): New.
	(gdb_argv): New class.
	* utils.c (gdb_argv::reset): New method.
	* tracepoint.c (delete_trace_variable_command): Use gdb_argv.
	* tracefile.c (tsave_command): Use gdb_argv.
	* top.c (new_ui_command): Use gdb_argv.
	* symmisc.c (maintenance_print_symbols)
	(maintenance_print_msymbols, maintenance_expand_symtabs): Use gdb_argv.
	* symfile.c (symbol_file_command, generic_load)
	(remove_symbol_file_command): Use gdb_argv.
	* stack.c (backtrace_command): Use gdb_argv.
	* source.c (add_path, show_substitute_path_command)
	(unset_substitute_path_command, set_substitute_path_command):
	Use gdb_argv.
	* skip.c (skip_command): Use gdb_argv.  Use gdb_buildargv.
	* ser-mingw.c (pipe_windows_open): Use gdb_argv.
	* remote.c (extended_remote_run, remote_put_command)
	(remote_get_command, remote_delete_command): Use gdb_argv.
	* remote-sim.c (gdbsim_load, gdbsim_create_inferior)
	(gdbsim_open): Use gdb_argv.
	* python/py-cmd.c (gdbpy_string_to_argv): Use gdb_argv.
	* psymtab.c (maintenance_print_psymbols): Use gdb_argv.
	* procfs.c (procfs_info_proc): Use gdb_argv.
	* interps.c (interpreter_exec_cmd): Use gdb_argv.
	* infrun.c (handle_command): Use gdb_argv.
	* inferior.c (add_inferior_command, clone_inferior_command):
	Use gdb_argv.
	* guile/scm-string.c (gdbscm_string_to_argv): Use gdb_argv.
	* exec.c (exec_file_command): Use gdb_argv.
	* cli/cli-cmds.c (alias_command): Use gdb_argv.
	* compile/compile.c (build_argc_argv): Use gdb_argv.

gdb/source.c

@@ -484,16 +484,12 @@ add_path (char *dirname, char **which_path, int parse_separators)
 
   if (parse_separators)
     {
-      char **argv, **argvp;
-
       /* This will properly parse the space and tab separators
 	 and any quotes that may exist.  */
-      argv = gdb_buildargv (dirname);
+      gdb_argv argv (dirname);
 
-      for (argvp = argv; *argvp; argvp++)
-	dirnames_to_char_ptr_vec_append (&dir_vec, *argvp);
-
-      freeargv (argv);
+      for (char *arg : argv)
+	dirnames_to_char_ptr_vec_append (&dir_vec, arg);
     }
   else
     VEC_safe_push (char_ptr, dir_vec, xstrdup (dirname));
@@ -1883,12 +1879,9 @@ static void
 show_substitute_path_command (char *args, int from_tty)
 {
   struct substitute_path_rule *rule = substitute_path_rules;
-  char **argv;
   char *from = NULL;
-  struct cleanup *cleanup;
   
-  argv = gdb_buildargv (args);
-  cleanup = make_cleanup_freeargv (argv);
+  gdb_argv argv (args);
 
   /* We expect zero or one argument.  */
 
@@ -1912,8 +1905,6 @@ show_substitute_path_command (char *args, int from_tty)
         printf_filtered ("  `%s' -> `%s'.\n", rule->from, rule->to);
       rule = rule->next;
     }
-
-  do_cleanups (cleanup);
 }
 
 /* Implement the "unset substitute-path" command.  */
@@ -1922,14 +1913,12 @@ static void
 unset_substitute_path_command (char *args, int from_tty)
 {
   struct substitute_path_rule *rule = substitute_path_rules;
-  char **argv = gdb_buildargv (args);
+  gdb_argv argv (args);
   char *from = NULL;
   int rule_found = 0;
-  struct cleanup *cleanup;
 
   /* This function takes either 0 or 1 argument.  */
 
-  cleanup = make_cleanup_freeargv (argv);
   if (argv != NULL && argv[0] != NULL && argv[1] != NULL)
     error (_("Incorrect usage, too many arguments in command"));
 
@@ -1967,8 +1956,6 @@ unset_substitute_path_command (char *args, int from_tty)
     error (_("No substitution rule defined for `%s'"), from);
 
   forget_cached_source_info ();
-
-  do_cleanups (cleanup);
 }
 
 /* Add a new source path substitution rule.  */
@@ -1976,12 +1963,9 @@ unset_substitute_path_command (char *args, int from_tty)
 static void
 set_substitute_path_command (char *args, int from_tty)
 {
-  char **argv;
   struct substitute_path_rule *rule;
-  struct cleanup *cleanup;
   
-  argv = gdb_buildargv (args);
-  cleanup = make_cleanup_freeargv (argv);
+  gdb_argv argv (args);
 
   if (argv == NULL || argv[0] == NULL || argv [1] == NULL)
     error (_("Incorrect usage, too few arguments in command"));
@@ -2008,8 +1992,6 @@ set_substitute_path_command (char *args, int from_tty)
 
   add_substitute_path_rule (argv[0], argv[1]);
   forget_cached_source_info ();
-
-  do_cleanups (cleanup);
 }