gdb: Setting setter return a bool to tell if the value changed

GDB can notify observers when a parameter is changed.

To do that, do_set_command (in gdb/cli/cli-setshow.c) compares the new
value against the old one before updating it, and based on that notifies
observers.  This looks like something like:

    int valuechanged = 0;
    switch (cmd->var.type ())
    {
    case var_integer:
      {
        LONGEST new_val = parse_and_eval_long (arg)
        if (new_val != cmd->var.get<int> ())
        {
          cmd->var.get<int> (new_val);
          value_changes = 1;
        }
      }
      break;
    case var_string:
      {
        std::string val = std::string (arg);
        if (new_val != cmd->var.get<std::string> ())
        {
          cmd->var.get<std::string> (new_val);
          value_changes = 1;
        }
      }
      break;
    case...
      /* And so on for all possible var_types.  */
    }

This comparison is done for each possible var_type, which leads to
unnecessary code duplication.

In this patch I propose to move all those checks in one place within the
setting setter method.  This limits the code duplication and simplifies
the do_set_command implementation.

This patch also changes slightly the way a value change is detected.
Instead of comparing the user provided value against the current value
of the setting, we compare the value of the setting before and after the
set operation.  This is meant to handle edge cases where trying to set
an unrecognized value would be equivalent to a noop (the actual value
remains unchanged).

There should be no user visible change introduced by this commit.

Tested on x86_64 GNU/Linux.

[1] https://review.lttng.org/c/binutils-gdb/+/5831/41

Change-Id: If064b9cede3eb56275aacd2b286f74eceb1aed11

gdb/auto-load.c

@@ -137,7 +137,7 @@ show_auto_load_local_gdbinit (struct ui_file *file, int from_tty,
 /* Directory list from which to load auto-loaded scripts.  It is not checked
    for absolute paths but they are strongly recommended.  It is initialized by
    _initialize_auto_load.  */
-static char *auto_load_dir;
+static std::string auto_load_dir = AUTO_LOAD_DIR;
 
 /* "set" command for the auto_load_dir configuration variable.  */
 
@@ -145,11 +145,8 @@ static void
 set_auto_load_dir (const char *args, int from_tty, struct cmd_list_element *c)
 {
   /* Setting the variable to "" resets it to the compile time defaults.  */
-  if (auto_load_dir[0] == '\0')
-    {
-      xfree (auto_load_dir);
-      auto_load_dir = xstrdup (AUTO_LOAD_DIR);
-    }
+  if (auto_load_dir.empty ())
+    auto_load_dir = AUTO_LOAD_DIR;
 }
 
 /* "show" command for the auto_load_dir configuration variable.  */
@@ -166,7 +163,7 @@ show_auto_load_dir (struct ui_file *file, int from_tty,
 /* Directory list safe to hold auto-loaded files.  It is not checked for
    absolute paths but they are strongly recommended.  It is initialized by
    _initialize_auto_load.  */
-static char *auto_load_safe_path;
+static std::string auto_load_safe_path = AUTO_LOAD_SAFE_PATH;
 
 /* Vector of directory elements of AUTO_LOAD_SAFE_PATH with each one normalized
    by tilde_expand and possibly each entries has added its gdb_realpath
@@ -181,7 +178,7 @@ auto_load_expand_dir_vars (const char *string)
 {
   char *s = xstrdup (string);
   substitute_path_component (&s, "$datadir", gdb_datadir.c_str ());
-  substitute_path_component (&s, "$debugdir", debug_file_directory);
+  substitute_path_component (&s, "$debugdir", debug_file_directory.c_str ());
 
   if (debug_auto_load && strcmp (s, string) != 0)
     auto_load_debug_printf ("Expanded $-variables to \"%s\".", s);
@@ -199,9 +196,10 @@ static void
 auto_load_safe_path_vec_update (void)
 {
   auto_load_debug_printf ("Updating directories of \"%s\".",
-			  auto_load_safe_path);
+			  auto_load_safe_path.c_str ());
 
-  auto_load_safe_path_vec = auto_load_expand_dir_vars (auto_load_safe_path);
+  auto_load_safe_path_vec
+    = auto_load_expand_dir_vars (auto_load_safe_path.c_str ());
   size_t len = auto_load_safe_path_vec.size ();
 
   /* Apply tilde_expand and gdb_realpath to each AUTO_LOAD_SAFE_PATH_VEC
@@ -253,11 +251,8 @@ set_auto_load_safe_path (const char *args,
 			 int from_tty, struct cmd_list_element *c)
 {
   /* Setting the variable to "" resets it to the compile time defaults.  */
-  if (auto_load_safe_path[0] == '\0')
-    {
-      xfree (auto_load_safe_path);
-      auto_load_safe_path = xstrdup (AUTO_LOAD_SAFE_PATH);
-    }
+  if (auto_load_safe_path.empty ())
+    auto_load_safe_path = AUTO_LOAD_SAFE_PATH;
 
   auto_load_safe_path_vec_update ();
 }
@@ -291,17 +286,14 @@ show_auto_load_safe_path (struct ui_file *file, int from_tty,
 static void
 add_auto_load_safe_path (const char *args, int from_tty)
 {
-  char *s;
-
   if (args == NULL || *args == 0)
     error (_("\
 Directory argument required.\n\
 Use 'set auto-load safe-path /' for disabling the auto-load safe-path security.\
 "));
 
-  s = xstrprintf ("%s%c%s", auto_load_safe_path, DIRNAME_SEPARATOR, args);
-  xfree (auto_load_safe_path);
-  auto_load_safe_path = s;
+  auto_load_safe_path = string_printf ("%s%c%s", auto_load_safe_path.c_str (),
+				       DIRNAME_SEPARATOR, args);
 
   auto_load_safe_path_vec_update ();
 }
@@ -312,14 +304,11 @@ Use 'set auto-load safe-path /' for disabling the auto-load safe-path security.\
 static void
 add_auto_load_dir (const char *args, int from_tty)
 {
-  char *s;
-
   if (args == NULL || *args == 0)
     error (_("Directory argument required."));
 
-  s = xstrprintf ("%s%c%s", auto_load_dir, DIRNAME_SEPARATOR, args);
-  xfree (auto_load_dir);
-  auto_load_dir = s;
+  auto_load_dir = string_printf ("%s%c%s", auto_load_dir.c_str (),
+				 DIRNAME_SEPARATOR, args);
 }
 
 /* Implementation for filename_is_in_pattern overwriting the caller's FILENAME
@@ -459,7 +448,7 @@ file_is_auto_load_safe (const char *filename)
   warning (_("File \"%ps\" auto-loading has been declined by your "
 	     "`auto-load safe-path' set to \"%s\"."),
 	   styled_string (file_name_style.style (), filename_real.get ()),
-	   auto_load_safe_path);
+	   auto_load_safe_path.c_str ());
 
   if (!advice_printed)
     {
@@ -749,11 +738,11 @@ auto_load_objfile_script_1 (struct objfile *objfile, const char *realname,
 	 directory.  */
 
       std::vector<gdb::unique_xmalloc_ptr<char>> vec
-	= auto_load_expand_dir_vars (auto_load_dir);
+	= auto_load_expand_dir_vars (auto_load_dir.c_str ());
 
       auto_load_debug_printf
 	("Searching 'set auto-load scripts-directory' path \"%s\".",
-	 auto_load_dir);
+	 auto_load_dir.c_str ());
 
       /* Convert Windows file name from c:/dir/file to /c/dir/file.  */
       if (HAS_DRIVE_SPEC (debugfile))
@@ -1408,7 +1397,7 @@ set_auto_load_cmd (const char *args, int from_tty)
 	     "otherwise check the auto-load sub-commands."));
 
   for (list = *auto_load_set_cmdlist_get (); list != NULL; list = list->next)
-    if (list->var_type == var_boolean)
+    if (list->var->type () == var_boolean)
       {
 	gdb_assert (list->type == set_cmd);
 	do_set_command (args, from_tty, list);
@@ -1542,8 +1531,6 @@ This option has security implications for untrusted inferiors."),
 Usage: info auto-load local-gdbinit"),
 	   auto_load_info_cmdlist_get ());
 
-  auto_load_dir = xstrdup (AUTO_LOAD_DIR);
-
   suffix = ext_lang_auto_load_suffix (get_ext_lang_defn (EXT_LANG_GDB));
   gdb_name_help
     = xstrprintf (_("\
@@ -1595,7 +1582,6 @@ Show the list of directories from which to load auto-loaded scripts."),
   xfree (gdb_name_help);
   xfree (guile_name_help);
 
-  auto_load_safe_path = xstrdup (AUTO_LOAD_SAFE_PATH);
   auto_load_safe_path_vec_update ();
   add_setshow_optional_filename_cmd ("safe-path", class_support,
 				     &auto_load_safe_path, _("\

gdb/breakpoint.c

@@ -276,7 +276,7 @@ static const char *dprintf_style = dprintf_style_gdb;
    copied into the command, so it can be anything that GDB can
    evaluate to a callable address, not necessarily a function name.  */
 
-static char *dprintf_function;
+static std::string dprintf_function = "printf";
 
 /* The channel to use for dynamic printf if the preferred style is to
    call into the inferior; if a nonempty string, it will be passed to
@@ -286,7 +286,7 @@ static char *dprintf_function;
    "stderr", this could be an app-specific expression like
    "mystreams[curlogger]".  */
 
-static char *dprintf_channel;
+static std::string dprintf_channel;
 
 /* True if dprintf commands should continue to operate even if GDB
    has disconnected.  */
@@ -6672,7 +6672,7 @@ default_collect_info (void)
   /* If it has no value (which is frequently the case), say nothing; a
      message like "No default-collect." gets in user's face when it's
      not wanted.  */
-  if (!*default_collect)
+  if (default_collect.empty ())
     return;
 
   /* The following phrase lines up nicely with per-tracepoint collect
@@ -8773,17 +8773,17 @@ update_dprintf_command_list (struct breakpoint *b)
     printf_line = xstrprintf ("printf %s", dprintf_args);
   else if (strcmp (dprintf_style, dprintf_style_call) == 0)
     {
-      if (!dprintf_function)
+      if (dprintf_function.empty ())
 	error (_("No function supplied for dprintf call"));
 
-      if (dprintf_channel && strlen (dprintf_channel) > 0)
+      if (!dprintf_channel.empty ())
 	printf_line = xstrprintf ("call (void) %s (%s,%s)",
-				  dprintf_function,
-				  dprintf_channel,
+				  dprintf_function.c_str (),
+				  dprintf_channel.c_str (),
 				  dprintf_args);
       else
 	printf_line = xstrprintf ("call (void) %s (%s)",
-				  dprintf_function,
+				  dprintf_function.c_str (),
 				  dprintf_args);
     }
   else if (strcmp (dprintf_style, dprintf_style_agent) == 0)
@@ -15116,8 +15116,8 @@ save_breakpoints (const char *filename, int from_tty,
 	}
     }
 
-  if (extra_trace_bits && *default_collect)
-    fp.printf ("set default-collect %s\n", default_collect);
+  if (extra_trace_bits && !default_collect.empty ())
+    fp.printf ("set default-collect %s\n", default_collect.c_str ());
 
   if (from_tty)
     printf_filtered (_("Saved to file '%s'.\n"), expanded_filename.get ());
@@ -16028,7 +16028,6 @@ output stream by setting dprintf-function and dprintf-channel."),
 			update_dprintf_commands, NULL,
 			&setlist, &showlist);
 
-  dprintf_function = xstrdup ("printf");
   add_setshow_string_cmd ("dprintf-function", class_support,
 			  &dprintf_function, _("\
 Set the function to use for dynamic printf."), _("\
@@ -16036,7 +16035,6 @@ Show the function to use for dynamic printf."), NULL,
 			  update_dprintf_commands, NULL,
 			  &setlist, &showlist);
 
-  dprintf_channel = xstrdup ("");
   add_setshow_string_cmd ("dprintf-channel", class_support,
 			  &dprintf_channel, _("\
 Set the channel to use for dynamic printf."), _("\

gdb/build-id.c

@@ -130,7 +130,7 @@ build_id_to_bfd_suffix (size_t build_id_len, const bfd_byte *build_id,
      cause "/.build-id/..." lookups.  */
 
   std::vector<gdb::unique_xmalloc_ptr<char>> debugdir_vec
-    = dirnames_to_char_ptr_vec (debug_file_directory);
+    = dirnames_to_char_ptr_vec (debug_file_directory.c_str ());
 
   for (const gdb::unique_xmalloc_ptr<char> &debugdir : debugdir_vec)
     {
@@ -167,7 +167,7 @@ build_id_to_bfd_suffix (size_t build_id_len, const bfd_byte *build_id,
 	 Don't do it if the sysroot is the target system ("target:").  It
 	 could work in theory, but the lrealpath in build_id_to_debug_bfd_1
 	 only works with local paths.  */
-      if (strcmp (gdb_sysroot, TARGET_SYSROOT_PREFIX) != 0)
+      if (gdb_sysroot != TARGET_SYSROOT_PREFIX)
 	{
 	  link = gdb_sysroot + link;
 	  debug_bfd = build_id_to_debug_bfd_1 (link, build_id_len, build_id);

gdb/cli/cli-cmds.c

@@ -232,7 +232,7 @@ with_command_1 (const char *set_cmd_prefix,
 					  /*ignore_help_classes=*/ 1);
   gdb_assert (set_cmd != nullptr);
 
-  if (set_cmd->var == nullptr)
+  if (!set_cmd->var.has_value ())
     error (_("Cannot use this setting with the \"with\" command"));
 
   std::string temp_value
@@ -241,7 +241,7 @@ with_command_1 (const char *set_cmd_prefix,
   if (nested_cmd == nullptr)
     nested_cmd = skip_spaces (delim + 2);
 
-  std::string org_value = get_setshow_command_value_string (set_cmd);
+  std::string org_value = get_setshow_command_value_string (*set_cmd->var);
 
   /* Tweak the setting to the new temporary value.  */
   do_set_command (temp_value.c_str (), from_tty, set_cmd);
@@ -645,7 +645,7 @@ find_and_open_script (const char *script_file, int search_path)
   /* Search for and open 'file' on the search path used for source
      files.  Put the full location in *FULL_PATHP.  */
   gdb::unique_xmalloc_ptr<char> full_path;
-  fd = openp (source_path, search_flags,
+  fd = openp (source_path.c_str (), search_flags,
 	      file.get (), O_RDONLY, &full_path);
 
   if (fd == -1)
@@ -1037,12 +1037,7 @@ edit_command (const char *arg, int from_tty)
 struct pipe_cmd_opts
 {
   /* For "-d".  */
-  char *delimiter = nullptr;
-
-  ~pipe_cmd_opts ()
-  {
-    xfree (delimiter);
-  }
+  std::string delimiter;
 };
 
 static const gdb::option::option_def pipe_cmd_option_defs[] = {
@@ -1079,8 +1074,8 @@ pipe_command (const char *arg, int from_tty)
     (&arg, gdb::option::PROCESS_OPTIONS_UNKNOWN_IS_OPERAND, grp);
 
   const char *delim = "|";
-  if (opts.delimiter != nullptr)
-    delim = opts.delimiter;
+  if (!opts.delimiter.empty ())
+    delim = opts.delimiter.c_str ();
 
   const char *command = arg;
   if (command == nullptr)
@@ -1143,8 +1138,8 @@ pipe_command_completer (struct cmd_list_element *ignore,
     return;
 
   const char *delimiter = "|";
-  if (opts.delimiter != nullptr)
-    delimiter = opts.delimiter;
+  if (!opts.delimiter.empty ())
+    delimiter = opts.delimiter.c_str ();
 
   /* Check if we're past option values already.  */
   if (text > org_text && !isspace (text[-1]))
@@ -2088,31 +2083,31 @@ setting_cmd (const char *fnname, struct cmd_list_element *showlist,
 /* Builds a value from the show CMD.  */
 
 static struct value *
-value_from_setting (const cmd_list_element *cmd, struct gdbarch *gdbarch)
+value_from_setting (const setting &var, struct gdbarch *gdbarch)
 {
-  switch (cmd->var_type)
+  switch (var.type ())
     {
     case var_integer:
-      if (*(int *) cmd->var == INT_MAX)
+      if (var.get<int> () == INT_MAX)
 	return value_from_longest (builtin_type (gdbarch)->builtin_int,
 				   0);
       else
 	return value_from_longest (builtin_type (gdbarch)->builtin_int,
-				   *(int *) cmd->var);
+				   var.get<int> ());
     case var_zinteger:
       return value_from_longest (builtin_type (gdbarch)->builtin_int,
-				 *(int *) cmd->var);
+				 var.get<int> ());
     case var_boolean:
       return value_from_longest (builtin_type (gdbarch)->builtin_int,
-				 *(bool *) cmd->var ? 1 : 0);
+				 var.get<bool> () ? 1 : 0);
     case var_zuinteger_unlimited:
       return value_from_longest (builtin_type (gdbarch)->builtin_int,
-				 *(int *) cmd->var);
+				 var.get<int> ());
     case var_auto_boolean:
       {
 	int val;
 
-	switch (*(enum auto_boolean*) cmd->var)
+	switch (var.get<enum auto_boolean> ())
 	  {
 	  case AUTO_BOOLEAN_TRUE:
 	    val = 1;
@@ -2130,27 +2125,35 @@ value_from_setting (const cmd_list_element *cmd, struct gdbarch *gdbarch)
 				   val);
       }
     case var_uinteger:
-      if (*(unsigned int *) cmd->var == UINT_MAX)
+      if (var.get<unsigned int> () == UINT_MAX)
 	return value_from_ulongest
 	  (builtin_type (gdbarch)->builtin_unsigned_int, 0);
       else
 	return value_from_ulongest
 	  (builtin_type (gdbarch)->builtin_unsigned_int,
-	   *(unsigned int *) cmd->var);
+	   var.get<unsigned int> ());
     case var_zuinteger:
       return value_from_ulongest (builtin_type (gdbarch)->builtin_unsigned_int,
-				  *(unsigned int *) cmd->var);
+				  var.get<unsigned int> ());
     case var_string:
     case var_string_noescape:
     case var_optional_filename:
     case var_filename:
     case var_enum:
-      if (*(char **) cmd->var)
-	return value_cstring (*(char **) cmd->var, strlen (*(char **) cmd->var),
-			      builtin_type (gdbarch)->builtin_char);
-      else
-	return value_cstring ("", 1,
-			      builtin_type (gdbarch)->builtin_char);
+      {
+        std::string value;
+	if (var.type () == var_enum)
+	  value = var.get<const char *> ();
+	else
+	  value = var.get<std::string> ();
+
+	if (!value.empty ())
+	  return value_cstring (value.c_str (), value.length (),
+				builtin_type (gdbarch)->builtin_char);
+	else
+	  return value_cstring ("", 1,
+				builtin_type (gdbarch)->builtin_char);
+      }
     default:
       gdb_assert_not_reached ("bad var_type");
     }
@@ -2163,9 +2166,12 @@ gdb_setting_internal_fn (struct gdbarch *gdbarch,
 			 const struct language_defn *language,
 			 void *cookie, int argc, struct value **argv)
 {
-  return value_from_setting (setting_cmd ("$_gdb_setting", showlist,
-					  argc, argv),
-			     gdbarch);
+  cmd_list_element *show_cmd
+    = setting_cmd ("$_gdb_setting", showlist, argc, argv);
+
+  gdb_assert (show_cmd->var.has_value ());
+
+  return value_from_setting (*show_cmd->var, gdbarch);
 }
 
 /* Implementation of the convenience function $_gdb_maint_setting.  */
@@ -2175,18 +2181,20 @@ gdb_maint_setting_internal_fn (struct gdbarch *gdbarch,
 			       const struct language_defn *language,
 			       void *cookie, int argc, struct value **argv)
 {
-  return value_from_setting (setting_cmd ("$_gdb_maint_setting",
-					  maintenance_show_cmdlist,
-					  argc, argv),
-			     gdbarch);
+  cmd_list_element *show_cmd
+    = setting_cmd ("$_gdb_maint_setting", maintenance_show_cmdlist, argc, argv);
+
+  gdb_assert (show_cmd->var.has_value ());
+
+  return value_from_setting (*show_cmd->var, gdbarch);
 }
 
 /* Builds a string value from the show CMD.  */
 
 static struct value *
-str_value_from_setting (const cmd_list_element *cmd, struct gdbarch *gdbarch)
+str_value_from_setting (const setting &var, struct gdbarch *gdbarch)
 {
-  switch (cmd->var_type)
+  switch (var.type ())
     {
     case var_integer:
     case var_zinteger:
@@ -2196,7 +2204,7 @@ str_value_from_setting (const cmd_list_element *cmd, struct gdbarch *gdbarch)
     case var_uinteger:
     case var_zuinteger:
       {
-	std::string cmd_val = get_setshow_command_value_string (cmd);
+	std::string cmd_val = get_setshow_command_value_string (var);
 
 	return value_cstring (cmd_val.c_str (), cmd_val.size (),
 			      builtin_type (gdbarch)->builtin_char);
@@ -2209,15 +2217,22 @@ str_value_from_setting (const cmd_list_element *cmd, struct gdbarch *gdbarch)
     case var_enum:
       /* For these cases, we do not use get_setshow_command_value_string,
 	 as this function handle some characters specially, e.g. by
-	 escaping quotes.  So, we directly use the cmd->var string value,
-	 similarly to the value_from_setting code for these cases.  */
-      if (*(char **) cmd->var)
-	return value_cstring (*(char **) cmd->var, strlen (*(char **) cmd->var),
-			      builtin_type (gdbarch)->builtin_char);
-      else
-	return value_cstring ("", 1,
-			      builtin_type (gdbarch)->builtin_char);
+	 escaping quotevar.  So, we directly use the cmd->var string value,
+	 similarly to the value_from_setting code for these casevar.  */
+      {
+        std::string value;
+	if (var.type () == var_enum)
+	  value = var.get<const char *> ();
+	else
+	  value = var.get<std::string> ();
 
+	if (!value.empty ())
+	  return value_cstring (value.c_str (), value.length (),
+				builtin_type (gdbarch)->builtin_char);
+	else
+	  return value_cstring ("", 1,
+				builtin_type (gdbarch)->builtin_char);
+      }
     default:
       gdb_assert_not_reached ("bad var_type");
     }
@@ -2230,9 +2245,12 @@ gdb_setting_str_internal_fn (struct gdbarch *gdbarch,
 			     const struct language_defn *language,
 			     void *cookie, int argc, struct value **argv)
 {
-  return str_value_from_setting (setting_cmd ("$_gdb_setting_str",
-					      showlist, argc, argv),
-				 gdbarch);
+  cmd_list_element *show_cmd
+    = setting_cmd ("$_gdb_setting_str", showlist, argc, argv);
+
+  gdb_assert (show_cmd->var.has_value ());
+
+  return str_value_from_setting (*show_cmd->var, gdbarch);
 }
 
 
@@ -2243,10 +2261,13 @@ gdb_maint_setting_str_internal_fn (struct gdbarch *gdbarch,
 				   const struct language_defn *language,
 				   void *cookie, int argc, struct value **argv)
 {
-  return str_value_from_setting (setting_cmd ("$_gdb_maint_setting_str",
-					      maintenance_show_cmdlist,
-					      argc, argv),
-				 gdbarch);
+  cmd_list_element *show_cmd
+    = setting_cmd ("$_gdb_maint_setting_str", maintenance_show_cmdlist, argc,
+		   argv);
+
+  gdb_assert (show_cmd->var.has_value ());
+
+  return str_value_from_setting (*show_cmd->var, gdbarch);
 }
 
 void _initialize_cli_cmds ();

gdb/cli/cli-decode.c

@@ -460,14 +460,21 @@ empty_func (const char *args, int from_tty, cmd_list_element *c)
    CLASS is as in add_cmd.
    VAR_TYPE is the kind of thing we are setting.
    VAR is address of the variable being controlled by this command.
+   SET_SETTING_FUNC is a pointer to an optional function callback used to set
+   the setting value.
+   GET_SETTING_FUNC is a pointer to an optional function callback used to get
+   the setting value.
    DOC is the documentation string.  */
 
+template<typename T>
 static struct cmd_list_element *
 add_set_or_show_cmd (const char *name,
 		     enum cmd_types type,
 		     enum command_class theclass,
 		     var_types var_type,
-		     void *var,
+		     T *var,
+		     setting_setter_ftype<T> set_setting_func,
+		     setting_getter_ftype<T> get_setting_func,
 		     const char *doc,
 		     struct cmd_list_element **list)
 {
@@ -475,8 +482,14 @@ add_set_or_show_cmd (const char *name,
 
   gdb_assert (type == set_cmd || type == show_cmd);
   c->type = type;
-  c->var_type = var_type;
-  c->var = var;
+
+  gdb_assert ((var != nullptr)
+	      != (set_setting_func != nullptr && get_setting_func != nullptr));
+  if (var != nullptr)
+    c->var.emplace (var_type, var);
+  else
+    c->var.emplace (var_type, set_setting_func, get_setting_func);
+
   /* This needs to be something besides NULL so that this isn't
      treated as a help class.  */
   c->func = empty_func;
@@ -486,18 +499,23 @@ add_set_or_show_cmd (const char *name,
 /* Add element named NAME to both the command SET_LIST and SHOW_LIST.
    CLASS is as in add_cmd.  VAR_TYPE is the kind of thing we are
    setting.  VAR is address of the variable being controlled by this
-   command.  SET_FUNC and SHOW_FUNC are the callback functions (if
-   non-NULL).  SET_DOC, SHOW_DOC and HELP_DOC are the documentation
-   strings.
+   command.  If nullptr is given as VAR, then both SET_SETTING_FUNC and
+   GET_SETTING_FUNC must be provided. SET_SETTING_FUNC and GET_SETTING_FUNC are
+   callbacks used to access and modify the underlying property, whatever its
+   storage is.  SET_FUNC and SHOW_FUNC are the callback functions (if non-NULL).
+   SET_DOC, SHOW_DOC and HELP_DOC are the documentation strings.
 
    Return the newly created set and show commands.  */
 
+template<typename T>
 static set_show_commands
 add_setshow_cmd_full (const char *name,
 		      enum command_class theclass,
-		      var_types var_type, void *var,
+		      var_types var_type, T *var,
 		      const char *set_doc, const char *show_doc,
 		      const char *help_doc,
+		      setting_setter_ftype<T> set_setting_func,
+		      setting_getter_ftype<T> get_setting_func,
 		      cmd_func_ftype *set_func,
 		      show_value_ftype *show_func,
 		      struct cmd_list_element **set_list,
@@ -518,15 +536,17 @@ add_setshow_cmd_full (const char *name,
       full_set_doc = xstrdup (set_doc);
       full_show_doc = xstrdup (show_doc);
     }
-  set = add_set_or_show_cmd (name, set_cmd, theclass, var_type, var,
-			     full_set_doc, set_list);
+  set = add_set_or_show_cmd<T> (name, set_cmd, theclass, var_type, var,
+				set_setting_func, get_setting_func,
+				full_set_doc, set_list);
   set->doc_allocated = 1;
 
   if (set_func != NULL)
     set->func = set_func;
 
-  show = add_set_or_show_cmd (name, show_cmd, theclass, var_type, var,
-			      full_show_doc, show_list);
+  show = add_set_or_show_cmd<T> (name, show_cmd, theclass, var_type, var,
+				 set_setting_func, get_setting_func,
+				 full_show_doc, show_list);
   show->doc_allocated = 1;
   show->show_value_func = show_func;
   /* Disable the default symbol completer.  Doesn't make much sense
@@ -555,14 +575,38 @@ add_setshow_enum_cmd (const char *name,
 		      struct cmd_list_element **show_list)
 {
   set_show_commands commands
-    =  add_setshow_cmd_full (name, theclass, var_enum, var,
-			     set_doc, show_doc, help_doc,
-			     set_func, show_func,
-			     set_list, show_list);
+    =  add_setshow_cmd_full<const char *> (name, theclass, var_enum, var,
+					   set_doc, show_doc, help_doc,
+					   nullptr, nullptr, set_func,
+					   show_func, set_list, show_list);
   commands.set->enums = enumlist;
   return commands;
 }
 
+/* Same as above but using a getter and a setter function instead of a pointer
+   to a global storage buffer.  */
+
+set_show_commands
+add_setshow_enum_cmd (const char *name, command_class theclass,
+		      const char *const *enumlist, const char *set_doc,
+		      const char *show_doc, const char *help_doc,
+		      setting_setter_ftype<const char *> set_func,
+		      setting_getter_ftype<const char *> get_func,
+		      show_value_ftype *show_func,
+		      cmd_list_element **set_list,
+		      cmd_list_element **show_list)
+{
+  auto cmds = add_setshow_cmd_full<const char *> (name, theclass, var_enum,
+						  nullptr, set_doc, show_doc,
+						  help_doc, set_func, get_func,
+						  nullptr, show_func, set_list,
+						  show_list);
+
+  cmds.set->enums = enumlist;
+
+  return cmds;
+}
+
 /* See cli-decode.h.  */
 const char * const auto_boolean_enums[] = { "on", "off", "auto", NULL };
 
@@ -583,16 +627,42 @@ add_setshow_auto_boolean_cmd (const char *name,
 			      struct cmd_list_element **show_list)
 {
   set_show_commands commands
-    = add_setshow_cmd_full (name, theclass, var_auto_boolean, var,
-			    set_doc, show_doc, help_doc,
-			    set_func, show_func,
-			    set_list, show_list);
+    = add_setshow_cmd_full<enum auto_boolean> (name, theclass, var_auto_boolean,
+					       var, set_doc, show_doc, help_doc,
+					       nullptr, nullptr, set_func,
+					       show_func, set_list, show_list);
 
   commands.set->enums = auto_boolean_enums;
 
   return commands;
 }
 
+/* Same as above but using a getter and a setter function instead of a pointer
+   to a global storage buffer.  */
+
+set_show_commands
+add_setshow_auto_boolean_cmd (const char *name, command_class theclass,
+			      const char *set_doc, const char *show_doc,
+			      const char *help_doc,
+			      setting_setter_ftype<enum auto_boolean> set_func,
+			      setting_getter_ftype<enum auto_boolean> get_func,
+			      show_value_ftype *show_func,
+			      cmd_list_element **set_list,
+			      cmd_list_element **show_list)
+{
+  auto cmds = add_setshow_cmd_full<enum auto_boolean> (name, theclass,
+						       var_auto_boolean,
+						       nullptr, set_doc,
+						       show_doc, help_doc,
+						       set_func, get_func,
+						       nullptr, show_func,
+						       set_list, show_list);
+
+  cmds.set->enums = auto_boolean_enums;
+
+  return cmds;
+}
+
 /* See cli-decode.h.  */
 const char * const boolean_enums[] = { "on", "off", NULL };
 
@@ -612,22 +682,45 @@ add_setshow_boolean_cmd (const char *name, enum command_class theclass, bool *va
 			 struct cmd_list_element **show_list)
 {
   set_show_commands commands
-    = add_setshow_cmd_full (name, theclass, var_boolean, var,
-			    set_doc, show_doc, help_doc,
-			    set_func, show_func,
-			    set_list, show_list);
+    = add_setshow_cmd_full<bool> (name, theclass, var_boolean, var,
+				  set_doc, show_doc, help_doc,
+				  nullptr, nullptr, set_func, show_func,
+				  set_list, show_list);
 
   commands.set->enums = boolean_enums;
 
   return commands;
 }
 
+/* Same as above but using a getter and a setter function instead of a pointer
+   to a global storage buffer.  */
+
+set_show_commands
+add_setshow_boolean_cmd (const char *name, command_class theclass,
+			 const char *set_doc, const char *show_doc,
+			 const char *help_doc,
+			 setting_setter_ftype<bool> set_func,
+			 setting_getter_ftype<bool> get_func,
+			 show_value_ftype *show_func,
+			 cmd_list_element **set_list,
+			 cmd_list_element **show_list)
+{
+  auto cmds = add_setshow_cmd_full<bool> (name, theclass, var_boolean, nullptr,
+					  set_doc, show_doc, help_doc,
+					  set_func, get_func, nullptr,
+					  show_func, set_list, show_list);
+
+  cmds.set->enums = boolean_enums;
+
+  return cmds;
+}
+
 /* Add element named NAME to both the set and show command LISTs (the
    list for set/show or some sublist thereof).  */
 
 set_show_commands
 add_setshow_filename_cmd (const char *name, enum command_class theclass,
-			  char **var,
+			  std::string *var,
 			  const char *set_doc, const char *show_doc,
 			  const char *help_doc,
 			  cmd_func_ftype *set_func,
@@ -636,22 +729,46 @@ add_setshow_filename_cmd (const char *name, enum command_class theclass,
 			  struct cmd_list_element **show_list)
 {
   set_show_commands commands
-    = add_setshow_cmd_full (name, theclass, var_filename, var,
-			    set_doc, show_doc, help_doc,
-			    set_func, show_func,
-			    set_list, show_list);
+    = add_setshow_cmd_full<std::string> (name, theclass, var_filename, var,
+					 set_doc, show_doc, help_doc,
+					 nullptr, nullptr, set_func,
+					 show_func, set_list, show_list);
 
   set_cmd_completer (commands.set, filename_completer);
 
   return commands;
 }
 
+/* Same as above but using a getter and a setter function instead of a pointer
+   to a global storage buffer.  */
+
+set_show_commands
+add_setshow_filename_cmd (const char *name, command_class theclass,
+			  const char *set_doc, const char *show_doc,
+			  const char *help_doc,
+			  setting_setter_ftype<std::string> set_func,
+			  setting_getter_ftype<std::string> get_func,
+			  show_value_ftype *show_func,
+			  cmd_list_element **set_list,
+			  cmd_list_element **show_list)
+{
+  auto cmds = add_setshow_cmd_full<std::string> (name, theclass, var_filename,
+						 nullptr, set_doc, show_doc,
+						 help_doc, set_func, get_func,
+						 nullptr, show_func, set_list,
+						 show_list);
+
+  set_cmd_completer (cmds.set, filename_completer);
+
+  return cmds;
+}
+
 /* Add element named NAME to both the set and show command LISTs (the
    list for set/show or some sublist thereof).  */
 
 set_show_commands
 add_setshow_string_cmd (const char *name, enum command_class theclass,
-			char **var,
+			std::string *var,
 			const char *set_doc, const char *show_doc,
 			const char *help_doc,
 			cmd_func_ftype *set_func,
@@ -660,10 +777,10 @@ add_setshow_string_cmd (const char *name, enum command_class theclass,
 			struct cmd_list_element **show_list)
 {
   set_show_commands commands
-    = add_setshow_cmd_full (name, theclass, var_string, var,
-			    set_doc, show_doc, help_doc,
-			    set_func, show_func,
-			    set_list, show_list);
+    = add_setshow_cmd_full<std::string> (name, theclass, var_string, var,
+					set_doc, show_doc, help_doc,
+					nullptr, nullptr, set_func,
+					show_func, set_list, show_list);
 
   /* Disable the default symbol completer.  */
   set_cmd_completer (commands.set, nullptr);
@@ -671,12 +788,37 @@ add_setshow_string_cmd (const char *name, enum command_class theclass,
   return commands;
 }
 
+/* Same as above but using a getter and a setter function instead of a pointer
+   to a global storage buffer.  */
+
+set_show_commands
+add_setshow_string_cmd (const char *name, command_class theclass,
+			const char *set_doc, const char *show_doc,
+			const char *help_doc,
+			setting_setter_ftype<std::string> set_func,
+			setting_getter_ftype<std::string> get_func,
+			show_value_ftype *show_func,
+			cmd_list_element **set_list,
+			cmd_list_element **show_list)
+{
+  auto cmds = add_setshow_cmd_full<std::string> (name, theclass, var_string,
+						 nullptr, set_doc, show_doc,
+						 help_doc, set_func, get_func,
+						 nullptr, show_func, set_list,
+						 show_list);
+
+  /* Disable the default symbol completer.  */
+  set_cmd_completer (cmds.set, nullptr);
+
+  return cmds;
+}
+
 /* Add element named NAME to both the set and show command LISTs (the
    list for set/show or some sublist thereof).  */
 
 set_show_commands
 add_setshow_string_noescape_cmd (const char *name, enum command_class theclass,
-				 char **var,
+				 std::string *var,
 				 const char *set_doc, const char *show_doc,
 				 const char *help_doc,
 				 cmd_func_ftype *set_func,
@@ -685,10 +827,10 @@ add_setshow_string_noescape_cmd (const char *name, enum command_class theclass,
 				 struct cmd_list_element **show_list)
 {
   set_show_commands commands
-    = add_setshow_cmd_full (name, theclass, var_string_noescape, var,
-			    set_doc, show_doc, help_doc,
-			    set_func, show_func,
-			    set_list, show_list);
+    = add_setshow_cmd_full<std::string> (name, theclass, var_string_noescape,
+					 var, set_doc, show_doc, help_doc,
+					 nullptr, nullptr, set_func, show_func,
+					 set_list, show_list);
 
   /* Disable the default symbol completer.  */
   set_cmd_completer (commands.set, nullptr);
@@ -696,12 +838,38 @@ add_setshow_string_noescape_cmd (const char *name, enum command_class theclass,
   return commands;
 }
 
+/* Same as above but using a getter and a setter function instead of a pointer
+   to a global storage buffer.  */
+
+set_show_commands
+add_setshow_string_noescape_cmd (const char *name, command_class theclass,
+				 const char *set_doc, const char *show_doc,
+				 const char *help_doc,
+				 setting_setter_ftype<std::string> set_func,
+				 setting_getter_ftype<std::string> get_func,
+				 show_value_ftype *show_func,
+				 cmd_list_element **set_list,
+				 cmd_list_element **show_list)
+{
+  auto cmds = add_setshow_cmd_full<std::string> (name, theclass,
+						 var_string_noescape, nullptr,
+						 set_doc, show_doc, help_doc,
+						 set_func, get_func,
+						 nullptr, show_func, set_list,
+						 show_list);
+
+  /* Disable the default symbol completer.  */
+  set_cmd_completer (cmds.set, nullptr);
+
+  return cmds;
+}
+
 /* Add element named NAME to both the set and show command LISTs (the
    list for set/show or some sublist thereof).  */
 
 set_show_commands
 add_setshow_optional_filename_cmd (const char *name, enum command_class theclass,
-				   char **var,
+				   std::string *var,
 				   const char *set_doc, const char *show_doc,
 				   const char *help_doc,
 				   cmd_func_ftype *set_func,
@@ -710,16 +878,40 @@ add_setshow_optional_filename_cmd (const char *name, enum command_class theclass
 				   struct cmd_list_element **show_list)
 {
   set_show_commands commands
-    = add_setshow_cmd_full (name, theclass, var_optional_filename, var,
-			    set_doc, show_doc, help_doc,
-			    set_func, show_func,
-			    set_list, show_list);
+    = add_setshow_cmd_full<std::string> (name, theclass, var_optional_filename,
+					 var, set_doc, show_doc, help_doc,
+					 nullptr, nullptr, set_func, show_func,
+					 set_list, show_list);
 		
   set_cmd_completer (commands.set, filename_completer);
 
   return commands;
 }
 
+/* Same as above but using a getter and a setter function instead of a pointer
+   to a global storage buffer.  */
+
+set_show_commands
+add_setshow_optional_filename_cmd (const char *name, command_class theclass,
+				   const char *set_doc, const char *show_doc,
+				   const char *help_doc,
+				   setting_setter_ftype<std::string> set_func,
+				   setting_getter_ftype<std::string> get_func,
+				   show_value_ftype *show_func,
+				   cmd_list_element **set_list,
+				   cmd_list_element **show_list)
+{
+  auto cmds =
+    add_setshow_cmd_full<std::string> (name, theclass, var_optional_filename,
+				       nullptr, set_doc, show_doc, help_doc,
+				       set_func, get_func, nullptr, show_func,
+				       set_list,show_list);
+
+  set_cmd_completer (cmds.set, filename_completer);
+
+  return cmds;
+}
+
 /* Completes on literal "unlimited".  Used by integer commands that
    support a special "unlimited" value.  */
 
@@ -754,16 +946,39 @@ add_setshow_integer_cmd (const char *name, enum command_class theclass,
 			 struct cmd_list_element **show_list)
 {
   set_show_commands commands
-    = add_setshow_cmd_full (name, theclass, var_integer, var,
-			    set_doc, show_doc, help_doc,
-			    set_func, show_func,
-			    set_list, show_list);
+    = add_setshow_cmd_full<int> (name, theclass, var_integer, var,
+				 set_doc, show_doc, help_doc,
+				 nullptr, nullptr, set_func,
+				 show_func, set_list, show_list);
 
   set_cmd_completer (commands.set, integer_unlimited_completer);
 
   return commands;
 }
 
+/* Same as above but using a getter and a setter function instead of a pointer
+   to a global storage buffer.  */
+
+set_show_commands
+add_setshow_integer_cmd (const char *name, command_class theclass,
+			 const char *set_doc, const char *show_doc,
+			 const char *help_doc,
+			 setting_setter_ftype<int> set_func,
+			 setting_getter_ftype<int> get_func,
+			 show_value_ftype *show_func,
+			 cmd_list_element **set_list,
+			 cmd_list_element **show_list)
+{
+  auto cmds = add_setshow_cmd_full<int> (name, theclass, var_integer, nullptr,
+					 set_doc, show_doc, help_doc, set_func,
+					 get_func, nullptr, show_func, set_list,
+					 show_list);
+
+  set_cmd_completer (cmds.set, integer_unlimited_completer);
+
+  return cmds;
+}
+
 /* Add element named NAME to both the set and show command LISTs (the
    list for set/show or some sublist thereof).  CLASS is as in
    add_cmd.  VAR is address of the variable which will contain the
@@ -780,16 +995,40 @@ add_setshow_uinteger_cmd (const char *name, enum command_class theclass,
 			  struct cmd_list_element **show_list)
 {
   set_show_commands commands
-    = add_setshow_cmd_full (name, theclass, var_uinteger, var,
-			    set_doc, show_doc, help_doc,
-			    set_func, show_func,
-			    set_list, show_list);
+    = add_setshow_cmd_full<unsigned int> (name, theclass, var_uinteger, var,
+					  set_doc, show_doc, help_doc,
+					  nullptr, nullptr, set_func,
+					  show_func, set_list, show_list);
 
   set_cmd_completer (commands.set, integer_unlimited_completer);
 
   return commands;
 }
 
+/* Same as above but using a getter and a setter function instead of a pointer
+   to a global storage buffer.  */
+
+set_show_commands
+add_setshow_uinteger_cmd (const char *name, command_class theclass,
+			  const char *set_doc, const char *show_doc,
+			  const char *help_doc,
+			  setting_setter_ftype<unsigned int> set_func,
+			  setting_getter_ftype<unsigned int> get_func,
+			  show_value_ftype *show_func,
+			  cmd_list_element **set_list,
+			  cmd_list_element **show_list)
+{
+  auto cmds = add_setshow_cmd_full<unsigned int> (name, theclass, var_uinteger,
+						  nullptr, set_doc, show_doc,
+						  help_doc, set_func, get_func,
+						  nullptr, show_func, set_list,
+						  show_list);
+
+  set_cmd_completer (cmds.set, integer_unlimited_completer);
+
+  return cmds;
+}
+
 /* Add element named NAME to both the set and show command LISTs (the
    list for set/show or some sublist thereof).  CLASS is as in
    add_cmd.  VAR is address of the variable which will contain the
@@ -805,10 +1044,29 @@ add_setshow_zinteger_cmd (const char *name, enum command_class theclass,
 			  struct cmd_list_element **set_list,
 			  struct cmd_list_element **show_list)
 {
-  return add_setshow_cmd_full (name, theclass, var_zinteger, var,
-			       set_doc, show_doc, help_doc,
-			       set_func, show_func,
-			       set_list, show_list);
+  return add_setshow_cmd_full<int> (name, theclass, var_zinteger, var,
+				    set_doc, show_doc, help_doc,
+				    nullptr, nullptr, set_func,
+				    show_func, set_list, show_list);
+}
+
+/* Same as above but using a getter and a setter function instead of a pointer
+   to a global storage buffer.  */
+
+set_show_commands
+add_setshow_zinteger_cmd (const char *name, command_class theclass,
+			  const char *set_doc, const char *show_doc,
+			  const char *help_doc,
+			  setting_setter_ftype<int> set_func,
+			  setting_getter_ftype<int> get_func,
+			  show_value_ftype *show_func,
+			  cmd_list_element **set_list,
+			  cmd_list_element **show_list)
+{
+  return add_setshow_cmd_full<int> (name, theclass, var_zinteger, nullptr,
+				    set_doc, show_doc, help_doc, set_func,
+				    get_func, nullptr, show_func, set_list,
+				    show_list);
 }
 
 set_show_commands
@@ -824,16 +1082,40 @@ add_setshow_zuinteger_unlimited_cmd (const char *name,
 				     struct cmd_list_element **show_list)
 {
   set_show_commands commands
-    = add_setshow_cmd_full (name, theclass, var_zuinteger_unlimited, var,
-			    set_doc, show_doc, help_doc,
-			    set_func, show_func,
-			    set_list, show_list);
+    = add_setshow_cmd_full<int> (name, theclass, var_zuinteger_unlimited, var,
+				 set_doc, show_doc, help_doc, nullptr,
+				 nullptr, set_func, show_func, set_list,
+				 show_list);
 
   set_cmd_completer (commands.set, integer_unlimited_completer);
 
   return commands;
 }
 
+/* Same as above but using a getter and a setter function instead of a pointer
+   to a global storage buffer.  */
+
+set_show_commands
+add_setshow_zuinteger_unlimited_cmd (const char *name, command_class theclass,
+				     const char *set_doc, const char *show_doc,
+				     const char *help_doc,
+				     setting_setter_ftype<int> set_func,
+				     setting_getter_ftype<int> get_func,
+				     show_value_ftype *show_func,
+				     cmd_list_element **set_list,
+				     cmd_list_element **show_list)
+{
+  auto cmds
+    = add_setshow_cmd_full<int> (name, theclass, var_zuinteger_unlimited,
+				 nullptr, set_doc, show_doc, help_doc, set_func,
+				 get_func, nullptr, show_func, set_list,
+				 show_list);
+
+  set_cmd_completer (cmds.set, integer_unlimited_completer);
+
+  return cmds;
+}
+
 /* Add element named NAME to both the set and show command LISTs (the
    list for set/show or some sublist thereof).  CLASS is as in
    add_cmd.  VAR is address of the variable which will contain the
@@ -849,10 +1131,30 @@ add_setshow_zuinteger_cmd (const char *name, enum command_class theclass,
 			   struct cmd_list_element **set_list,
 			   struct cmd_list_element **show_list)
 {
-  return add_setshow_cmd_full (name, theclass, var_zuinteger, var,
-			       set_doc, show_doc, help_doc,
-			       set_func, show_func,
-			       set_list, show_list);
+  return add_setshow_cmd_full<unsigned int> (name, theclass, var_zuinteger,
+					     var, set_doc, show_doc, help_doc,
+					     nullptr, nullptr, set_func,
+					     show_func, set_list, show_list);
+}
+
+/* Same as above but using a getter and a setter function instead of a pointer
+   to a global storage buffer.  */
+
+set_show_commands
+add_setshow_zuinteger_cmd (const char *name, command_class theclass,
+			   const char *set_doc, const char *show_doc,
+			   const char *help_doc,
+			   setting_setter_ftype<unsigned int> set_func,
+			   setting_getter_ftype<unsigned int> get_func,
+			   show_value_ftype *show_func,
+			   cmd_list_element **set_list,
+			   cmd_list_element **show_list)
+{
+  return add_setshow_cmd_full<unsigned int> (name, theclass, var_zuinteger,
+					     nullptr, set_doc, show_doc,
+					     help_doc, set_func, get_func,
+					     nullptr, show_func, set_list,
+					     show_list);
 }
 
 /* Remove the command named NAME from the command list.  Return the

gdb/cli/cli-decode.h

@@ -55,7 +55,6 @@ struct cmd_list_element
       allow_unknown (0),
       abbrev_flag (0),
       type (not_set_cmd),
-      var_type (var_boolean),
       doc (doc_)
   {
     memset (&function, 0, sizeof (function));
@@ -160,9 +159,6 @@ struct cmd_list_element
      or "show").  */
   ENUM_BITFIELD (cmd_types) type : 2;
 
-  /* What kind of variable is *VAR?  */
-  ENUM_BITFIELD (var_types) var_type : 4;
-
   /* Function definition of this command.  NULL for command class
      names and for help topics that are not really commands.  NOTE:
      cagney/2002-02-02: This function signature is evolving.  For
@@ -228,9 +224,8 @@ struct cmd_list_element
      used to finalize the CONTEXT field, if needed.  */
   void (*destroyer) (struct cmd_list_element *self, void *context) = nullptr;
 
-  /* Pointer to variable affected by "set" and "show".  Doesn't
-     matter if type is not_set.  */
-  void *var = nullptr;
+  /* Setting affected by "set" and "show".  Not used if type is not_set.  */
+  gdb::optional<setting> var;
 
   /* Pointer to NULL terminated list of enumerated values (like
      argv).  */

gdb/cli/cli-logging.c

@@ -25,7 +25,7 @@
 
 static char *saved_filename;
 
-static char *logging_filename;
+static std::string logging_filename = "gdb.txt";
 static void
 show_logging_filename (struct ui_file *file, int from_tty,
 		       struct cmd_list_element *c, const char *value)
@@ -102,7 +102,7 @@ handle_redirections (int from_tty)
     }
 
   stdio_file_up log (new no_terminal_escape_file ());
-  if (!log->open (logging_filename, logging_overwrite ? "w" : "a"))
+  if (!log->open (logging_filename.c_str (), logging_overwrite ? "w" : "a"))
     perror_with_name (_("set logging"));
 
   /* Redirects everything to gdb_stdout while this is running.  */
@@ -110,20 +110,20 @@ handle_redirections (int from_tty)
     {
       if (!logging_redirect)
 	fprintf_unfiltered (gdb_stdout, "Copying output to %s.\n",
-			    logging_filename);
+			    logging_filename.c_str ());
       else
 	fprintf_unfiltered (gdb_stdout, "Redirecting output to %s.\n",
-			    logging_filename);
+			    logging_filename.c_str ());
 
       if (!debug_redirect)
 	fprintf_unfiltered (gdb_stdout, "Copying debug output to %s.\n",
-			    logging_filename);
+			    logging_filename.c_str ());
       else
 	fprintf_unfiltered (gdb_stdout, "Redirecting debug output to %s.\n",
-			    logging_filename);
+			    logging_filename.c_str ());
     }
 
-  saved_filename = xstrdup (logging_filename);
+  saved_filename = xstrdup (logging_filename.c_str ());
 
   /* Let the interpreter do anything it needs.  */
   current_interp_set_logging (std::move (log), logging_redirect,
@@ -145,10 +145,8 @@ set_logging_on (const char *args, int from_tty)
   const char *rest = args;
 
   if (rest && *rest)
-    {
-      xfree (logging_filename);
-      logging_filename = xstrdup (rest);
-    }
+    logging_filename = rest;
+
   handle_redirections (from_tty);
 }
 
@@ -201,6 +199,7 @@ If debug redirect is on, debug will go only to the log file."),
 			   set_logging_redirect,
 			   show_logging_redirect,
 			   &set_logging_cmdlist, &show_logging_cmdlist);
+
   add_setshow_filename_cmd ("file", class_support, &logging_filename, _("\
 Set the current logfile."), _("\
 Show the current logfile."), _("\
@@ -212,6 +211,4 @@ The logfile is used when directing GDB's output."),
 	   _("Enable logging."), &set_logging_cmdlist);
   add_cmd ("off", class_support, set_logging_off,
 	   _("Disable logging."), &set_logging_cmdlist);
-
-  logging_filename = xstrdup ("gdb.txt");
 }

gdb/cli/cli-option.c

@@ -45,7 +45,7 @@ union option_value
   const char *enumeration;
 
   /* For var_string options.  This is malloc-allocated.  */
-  char *string;
+  std::string *string;
 };
 
 /* Holds an options definition and its value.  */
@@ -87,7 +87,7 @@ struct option_def_and_value
     if (value.has_value ())
       {
 	if (option.type == var_string)
-	  xfree (value->string);
+	  delete value->string;
       }
   }
 
@@ -439,7 +439,7 @@ parse_option (gdb::array_view<const option_def_group> options_group,
 	  error (_("-%s requires an argument"), match->name);
 
 	option_value val;
-	val.string = xstrdup (str.c_str ());
+	val.string = new std::string (std::move (str));
 	return option_def_and_value {*match, match_ctx, val};
       }
 
@@ -603,8 +603,7 @@ save_option_value_in_ctx (gdb::optional<option_def_and_value> &ov)
       break;
     case var_string:
       *ov->option.var_address.string (ov->option, ov->ctx)
-	= ov->value->string;
-      ov->value->string = nullptr;
+	= std::move (*ov->value->string);
       break;
     default:
       gdb_assert_not_reached ("unhandled option type");

gdb/cli/cli-option.h

@@ -86,7 +86,7 @@ public:
       unsigned int *(*uinteger) (const option_def &, void *ctx);
       int *(*integer) (const option_def &, void *ctx);
       const char **(*enumeration) (const option_def &, void *ctx);
-      char **(*string) (const option_def &, void *ctx);
+      std::string *(*string) (const option_def &, void *ctx);
     }
   var_address;
 
@@ -268,7 +268,7 @@ template<typename Context>
 struct string_option_def : option_def
 {
   string_option_def (const char *long_option_,
-		     char **(*get_var_address_cb_) (Context *),
+		     std::string *(*get_var_address_cb_) (Context *),
 		     show_value_ftype *show_cmd_cb_,
 		     const char *set_doc_,
 		     const char *show_doc_ = nullptr,

gdb/cli/cli-setshow.c

@@ -130,10 +130,14 @@ deprecated_show_value_hack (struct ui_file *ignore_file,
   /* If there's no command or value, don't try to print it out.  */
   if (c == NULL || value == NULL)
     return;
+
   /* Print doc minus "Show " at start.  Tell print_doc_line that
      this is for a 'show value' prefix.  */
   print_doc_line (gdb_stdout, c->doc + 5, true);
-  switch (c->var_type)
+
+  gdb_assert (c->var.has_value ());
+
+  switch (c->var->type ())
     {
     case var_string:
     case var_string_noescape:
@@ -142,6 +146,7 @@ deprecated_show_value_hack (struct ui_file *ignore_file,
     case var_enum:
       printf_filtered ((" is \"%s\".\n"), value);
       break;
+
     default:
       printf_filtered ((" is %s.\n"), value);
       break;
@@ -312,7 +317,9 @@ do_set_command (const char *arg, int from_tty, struct cmd_list_element *c)
   if (arg == NULL)
     arg = "";
 
-  switch (c->var_type)
+  gdb_assert (c->var.has_value ());
+
+  switch (c->var->type ())
     {
     case var_string:
       {
@@ -353,26 +360,12 @@ do_set_command (const char *arg, int from_tty, struct cmd_list_element *c)
 	*q++ = '\0';
 	newobj = (char *) xrealloc (newobj, q - newobj);
 
-	if (*(char **) c->var == NULL
-	    || strcmp (*(char **) c->var, newobj) != 0)
-	  {
-	    xfree (*(char **) c->var);
-	    *(char **) c->var = newobj;
-
-	    option_changed = true;
-	  }
-	else
-	  xfree (newobj);
+	option_changed = c->var->set<std::string> (std::string (newobj));
+	xfree (newobj);
       }
       break;
     case var_string_noescape:
-      if (*(char **) c->var == NULL || strcmp (*(char **) c->var, arg) != 0)
-	{
-	  xfree (*(char **) c->var);
-	  *(char **) c->var = xstrdup (arg);
-
-	  option_changed = true;
-	}
+      option_changed = c->var->set<std::string> (std::string (arg));
       break;
     case var_filename:
       if (*arg == '\0')
@@ -398,16 +391,9 @@ do_set_command (const char *arg, int from_tty, struct cmd_list_element *c)
 	else
 	  val = xstrdup ("");
 
-	if (*(char **) c->var == NULL
-	    || strcmp (*(char **) c->var, val) != 0)
-	  {
-	    xfree (*(char **) c->var);
-	    *(char **) c->var = val;
-
-	    option_changed = true;
-	  }
-	else
-	  xfree (val);
+	option_changed
+	  = c->var->set<std::string> (std::string (val));
+	xfree (val);
       }
       break;
     case var_boolean:
@@ -416,38 +402,18 @@ do_set_command (const char *arg, int from_tty, struct cmd_list_element *c)
 
 	if (val < 0)
 	  error (_("\"on\" or \"off\" expected."));
-	if (val != *(bool *) c->var)
-	  {
-	    *(bool *) c->var = val;
 
-	    option_changed = true;
-	  }
+	option_changed = c->var->set<bool> (val);
       }
       break;
     case var_auto_boolean:
-      {
-	enum auto_boolean val = parse_auto_binary_operation (arg);
-
-	if (*(enum auto_boolean *) c->var != val)
-	  {
-	    *(enum auto_boolean *) c->var = val;
-
-	    option_changed = true;
-	  }
-      }
+      option_changed = c->var->set<enum auto_boolean> (parse_auto_binary_operation (arg));
       break;
     case var_uinteger:
     case var_zuinteger:
-      {
-	unsigned int val = parse_cli_var_uinteger (c->var_type, &arg, true);
-
-	if (*(unsigned int *) c->var != val)
-	  {
-	    *(unsigned int *) c->var = val;
-
-	    option_changed = true;
-	  }
-      }
+      option_changed
+	= c->var->set<unsigned int> (parse_cli_var_uinteger (c->var->type (),
+							     &arg, true));
       break;
     case var_integer:
     case var_zinteger:
@@ -456,35 +422,30 @@ do_set_command (const char *arg, int from_tty, struct cmd_list_element *c)
 
 	if (*arg == '\0')
 	  {
-	    if (c->var_type == var_integer)
+	    if (c->var->type () == var_integer)
 	      error_no_arg (_("integer to set it to, or \"unlimited\"."));
 	    else
 	      error_no_arg (_("integer to set it to."));
 	  }
 
-	if (c->var_type == var_integer && is_unlimited_literal (&arg, true))
+	if (c->var->type () == var_integer && is_unlimited_literal (&arg, true))
 	  val = 0;
 	else
 	  val = parse_and_eval_long (arg);
 
-	if (val == 0 && c->var_type == var_integer)
+	if (val == 0 && c->var->type () == var_integer)
 	  val = INT_MAX;
 	else if (val < INT_MIN
 		 /* For var_integer, don't let the user set the value
 		    to INT_MAX directly, as that exposes an
 		    implementation detail to the user interface.  */
-		 || (c->var_type == var_integer && val >= INT_MAX)
-		 || (c->var_type == var_zinteger && val > INT_MAX))
+		 || (c->var->type () == var_integer && val >= INT_MAX)
+		 || (c->var->type () == var_zinteger && val > INT_MAX))
 	  error (_("integer %s out of range"), plongest (val));
 
-	if (*(int *) c->var != val)
-	  {
-	    *(int *) c->var = val;
-
-	    option_changed = true;
-	  }
-	break;
+	option_changed = c->var->set<int> (val);
       }
+      break;
     case var_enum:
       {
 	const char *end_arg = arg;
@@ -495,24 +456,12 @@ do_set_command (const char *arg, int from_tty, struct cmd_list_element *c)
 	if (*after != '\0')
 	  error (_("Junk after item \"%.*s\": %s"), len, arg, after);
 
-	if (*(const char **) c->var != match)
-	  {
-	    *(const char **) c->var = match;
-
-	    option_changed = true;
-	  }
+	option_changed = c->var->set<const char *> (match);
       }
       break;
     case var_zuinteger_unlimited:
-      {
-	int val = parse_cli_var_zuinteger_unlimited (&arg, true);
-
-	if (*(int *) c->var != val)
-	  {
-	    *(int *) c->var = val;
-	    option_changed = true;
-	  }
-      }
+      option_changed = c->var->set<int>
+	(parse_cli_var_zuinteger_unlimited (&arg, true));
       break;
     default:
       error (_("gdb internal error: bad var_type in do_setshow_command"));
@@ -578,25 +527,30 @@ do_set_command (const char *arg, int from_tty, struct cmd_list_element *c)
 
       xfree (cmds);
 
-      switch (c->var_type)
+      switch (c->var->type ())
 	{
 	case var_string:
 	case var_string_noescape:
 	case var_filename:
 	case var_optional_filename:
+	  gdb::observers::command_param_changed.notify
+	    (name, c->var->get<std::string> ().c_str ());
+	  break;
 	case var_enum:
-	  gdb::observers::command_param_changed.notify (name, *(char **) c->var);
+	  gdb::observers::command_param_changed.notify
+	    (name, c->var->get<const char *> ());
 	  break;
 	case var_boolean:
 	  {
-	    const char *opt = *(bool *) c->var ? "on" : "off";
+	    const char *opt = c->var->get<bool> () ? "on" : "off";
 
 	    gdb::observers::command_param_changed.notify (name, opt);
 	  }
 	  break;
 	case var_auto_boolean:
 	  {
-	    const char *s = auto_boolean_enums[*(enum auto_boolean *) c->var];
+	    const char *s
+	      = auto_boolean_enums[c->var->get<enum auto_boolean> ()];
 
 	    gdb::observers::command_param_changed.notify (name, s);
 	  }
@@ -606,7 +560,7 @@ do_set_command (const char *arg, int from_tty, struct cmd_list_element *c)
 	  {
 	    char s[64];
 
-	    xsnprintf (s, sizeof s, "%u", *(unsigned int *) c->var);
+	    xsnprintf (s, sizeof s, "%u", c->var->get<unsigned int> ());
 	    gdb::observers::command_param_changed.notify (name, s);
 	  }
 	  break;
@@ -616,7 +570,7 @@ do_set_command (const char *arg, int from_tty, struct cmd_list_element *c)
 	  {
 	    char s[64];
 
-	    xsnprintf (s, sizeof s, "%d", *(int *) c->var);
+	    xsnprintf (s, sizeof s, "%d", c->var->get<int> ());
 	    gdb::observers::command_param_changed.notify (name, s);
 	  }
 	  break;
@@ -628,28 +582,36 @@ do_set_command (const char *arg, int from_tty, struct cmd_list_element *c)
 /* See cli/cli-setshow.h.  */
 
 std::string
-get_setshow_command_value_string (const cmd_list_element *c)
+get_setshow_command_value_string (const setting &var)
 {
   string_file stb;
 
-  switch (c->var_type)
+  switch (var.type ())
     {
     case var_string:
-      if (*(char **) c->var)
-	stb.putstr (*(char **) c->var, '"');
+      {
+	std::string value = var.get<std::string> ();
+	if (!value.empty ())
+	  stb.putstr (value.c_str (), '"');
+      }
       break;
     case var_string_noescape:
     case var_optional_filename:
     case var_filename:
+      stb.puts (var.get<std::string> ().c_str ());
+      break;
     case var_enum:
-      if (*(char **) c->var)
-	stb.puts (*(char **) c->var);
+      {
+	const char *value = var.get<const char *> ();
+	if (value != nullptr)
+	  stb.puts (value);
+      }
       break;
     case var_boolean:
-      stb.puts (*(bool *) c->var ? "on" : "off");
+      stb.puts (var.get<bool> () ? "on" : "off");
       break;
     case var_auto_boolean:
-      switch (*(enum auto_boolean*) c->var)
+      switch (var.get<enum auto_boolean> ())
 	{
 	case AUTO_BOOLEAN_TRUE:
 	  stb.puts ("on");
@@ -667,26 +629,35 @@ get_setshow_command_value_string (const cmd_list_element *c)
       break;
     case var_uinteger:
     case var_zuinteger:
-      if (c->var_type == var_uinteger
-	  && *(unsigned int *) c->var == UINT_MAX)
-	stb.puts ("unlimited");
-      else
-	stb.printf ("%u", *(unsigned int *) c->var);
+      {
+	unsigned int const value = var.get<unsigned int> ();
+
+	if (var.type () == var_uinteger
+	    && value == UINT_MAX)
+	  stb.puts ("unlimited");
+	else
+	  stb.printf ("%u", value);
+      }
       break;
     case var_integer:
     case var_zinteger:
-      if (c->var_type == var_integer
-	  && *(int *) c->var == INT_MAX)
-	stb.puts ("unlimited");
-      else
-	stb.printf ("%d", *(int *) c->var);
+      {
+	int const value = var.get<int> ();
+
+	if (var.type () == var_integer
+	    && value == INT_MAX)
+	  stb.puts ("unlimited");
+	else
+	  stb.printf ("%d", value);
+      }
       break;
     case var_zuinteger_unlimited:
       {
-	if (*(int *) c->var == -1)
+	int const value = var.get<int> ();
+	if (value == -1)
 	  stb.puts ("unlimited");
 	else
-	  stb.printf ("%d", *(int *) c->var);
+	  stb.printf ("%d", value);
       }
       break;
     default:
@@ -708,8 +679,9 @@ do_show_command (const char *arg, int from_tty, struct cmd_list_element *c)
   struct ui_out *uiout = current_uiout;
 
   gdb_assert (c->type == show_cmd);
+  gdb_assert (c->var.has_value ());
 
-  std::string val = get_setshow_command_value_string (c);
+  std::string val = get_setshow_command_value_string (*c->var);
 
   /* FIXME: cagney/2005-02-10: There should be MI and CLI specific
      versions of code to print the value out.  */

gdb/cli/cli-setshow.h

@@ -57,8 +57,8 @@ extern void do_set_command (const char *arg, int from_tty,
 extern void do_show_command (const char *arg, int from_tty,
 			     struct cmd_list_element *c);
 
-/* Get a string version of C's current value.  */
-extern std::string get_setshow_command_value_string (const cmd_list_element *c);
+/* Get a string version of VAR's value.  */
+extern std::string get_setshow_command_value_string (const setting &var);
 
 extern void cmd_show_list (struct cmd_list_element *list, int from_tty);
 

gdb/command.h

@@ -97,16 +97,15 @@ typedef enum var_types
 
     /* String which the user enters with escapes (e.g. the user types
        \n and it is a real newline in the stored string).
-       *VAR is a malloc'd string, or NULL if the string is empty.  */
+       *VAR is a std::string, "" if the string is empty.  */
     var_string,
     /* String which stores what the user types verbatim.
-       *VAR is a malloc'd string, or NULL if the string is empty.  */
+       *VAR is std::string, "" if the string is empty.  */
     var_string_noescape,
-    /* String which stores a filename.  (*VAR) is a malloc'd string,
-       or "" if the string was empty.  */
+    /* String which stores a filename.  (*VAR) is a std::string,
+       "" if the string was empty.  */
     var_optional_filename,
-    /* String which stores a filename.  (*VAR) is a malloc'd
-       string.  */
+    /* String which stores a filename.  (*VAR) is a std::string.  */
     var_filename,
     /* ZeroableInteger.  *VAR is an int.  Like var_integer except
        that zero really means zero.  */
@@ -125,6 +124,206 @@ typedef enum var_types
   }
 var_types;
 
+/* Return true if a setting of type VAR_TYPE is backed with type T.
+
+   This function is left without definition intentionally.  This template is
+   specialized for all valid types that are used to back var_types.  Therefore
+   if one tries to instantiate this un-specialized template it means the T
+   parameter is not a type used to back a var_type and it is most likely a
+   programming error.  */
+template<typename T>
+inline bool var_type_uses (var_types var_type);
+
+/* Return true if a setting of type T is backed by a bool variable.  */
+template<>
+inline bool var_type_uses<bool> (var_types t)
+{
+  return t == var_boolean;
+};
+
+/* Return true if a setting of type T is backed by a auto_boolean variable.
+*/
+template<>
+inline bool var_type_uses<enum auto_boolean> (var_types t)
+{
+  return t == var_auto_boolean;
+}
+
+/* Return true if a setting of type T is backed by an unsigned int variable.
+*/
+template<>
+inline bool var_type_uses<unsigned int> (var_types t)
+{
+  return (t == var_uinteger || t == var_zinteger || t == var_zuinteger);
+}
+
+/* Return true if a setting of type T is backed by an int variable.  */
+template<>
+inline bool var_type_uses<int> (var_types t)
+{
+  return (t == var_integer || t == var_zinteger
+	  || t == var_zuinteger_unlimited);
+}
+
+/* Return true if a setting of type T is backed by a std::string variable.  */
+template<>
+inline bool var_type_uses<std::string> (var_types t)
+{
+  return (t == var_string || t == var_string_noescape
+	  || t == var_optional_filename || t == var_filename);
+}
+
+/* Return true if a setting of type T is backed by a const char * variable.
+*/
+template<>
+inline bool var_type_uses<const char *> (var_types t)
+{
+  return t == var_enum;
+}
+
+/* Function signature for a callback used to get a value from a setting.  */
+
+template<typename T>
+using setting_getter_ftype = T (*) ();
+
+/* Function signature for a callback used to set a value to a setting.  */
+
+template<typename T>
+using setting_setter_ftype = void (*) (T);
+
+/* Interface for getting and setting a setting's value.
+
+   The underlying data can be of any VAR_TYPES type.  */
+struct setting
+{
+  /* Create a setting backed by a variale of type T.
+
+     Type T must match the var type VAR_TYPE (see VAR_TYPE_USES).  */
+  template<typename T>
+  setting (var_types var_type, T *var)
+    : m_var_type (var_type), m_var (var)
+  {
+    gdb_assert (var != nullptr);
+    gdb_assert (var_type_uses<T> (var_type));
+  }
+
+  /* Create a setting backed by a variale, without verifying that the
+     underlying variable type matches VAR_TYPE.
+
+     This is only meant to be used by extension languages using this class
+     as a wrapper around their own setting data structure.  */
+  setting (var_types var_type, void *var)
+    : m_var_type (var_type), m_var (var)
+  {
+    gdb_assert (var != nullptr);
+  }
+
+  /* Create a setting backed by setter and getter functions
+
+     Type T must match the var type VAR_TYPE (see VAR_TYPE_USES).  */
+  template<typename T>
+  setting (var_types var_type,
+	   setting_setter_ftype<T> setter,
+	   setting_getter_ftype<T> getter)
+    : m_var_type (var_type)
+  {
+    gdb_assert (var_type_uses<T> (var_type));
+    gdb_assert (setter != nullptr);
+    gdb_assert (getter != nullptr);
+    this->m_setter = reinterpret_cast<void (*) ()> (setter);
+    this->m_getter = reinterpret_cast<void (*) ()> (getter);
+  }
+
+  /* Access the type of the current var.  */
+  var_types type () const
+  {
+    return m_var_type;
+  }
+
+  /* Return the current value (by pointer).
+
+     The template parameter T is the type of the variable used to store the
+     setting.
+
+     The returned value cannot be NULL (this is checked at runtime).  */
+  template<typename T>
+  T const *
+  get_p () const
+  {
+    gdb_assert (var_type_uses<T> (this->m_var_type));
+    gdb_assert (this->m_var != nullptr);
+
+    return static_cast<T const *> (this->m_var);
+  }
+
+  /* Return the current value.
+
+     If we have a user-provided getter, use it to get the setting's value.
+     Otherwise, return the value from the internally referenced buffer.
+
+     See get_p for discussion on the return type and template parameters.  */
+  template<typename T>
+  T get () const
+  {
+    gdb_assert (var_type_uses<T> (this->m_var_type));
+
+    if (m_getter != nullptr)
+      {
+	auto getter = reinterpret_cast<setting_getter_ftype<T>> (m_getter);
+	return getter ();
+      }
+    else
+      return *get_p<T> ();
+  }
+
+  /* Sets the value of the setting to V.
+
+     If we have a user-provided setter, use it to set the setting.  Otherwise
+     copy the value V to the internally referenced buffer.
+
+     The template parameter T indicates the type of the variable used to store
+     the setting.
+
+     The var_type of the setting must match T.  */
+  template<typename T>
+  bool set (T v)
+  {
+    /* Check that the current instance is of one of the supported types for
+       this instantiation.  */
+    gdb_assert (var_type_uses<T> (this->m_var_type));
+
+    const T old_value = this->get<T> ();
+
+    if (m_setter != nullptr)
+      {
+	auto setter = reinterpret_cast<setting_setter_ftype<T>> (m_setter);
+	setter (v);
+      }
+    else
+      {
+	gdb_assert (this->m_var != nullptr);
+	*static_cast<T *> (this->m_var) = v;
+      }
+
+    return old_value != this->get<T> ();
+  }
+
+protected:
+  /* The type of the variable M_VAR is pointing to, or that M_GETTER/M_SETTER
+     get/set.  */
+  var_types m_var_type;
+
+  /* Pointer to the enclosed variable.  The type of the variable is encoded
+     in M_VAR_TYPE.  */
+  void *m_var = nullptr;
+
+  /* Pointer to a user provided setter.  */
+  void (*m_setter) () = nullptr;
+
+  /* Pointer to a user provided getter.  */
+  void (*m_getter) () = nullptr;
+};
+
 /* This structure records one command'd definition.  */
 struct cmd_list_element;
 
@@ -406,39 +605,91 @@ extern set_show_commands add_setshow_enum_cmd
    show_value_ftype *show_func, cmd_list_element **set_list,
    cmd_list_element **show_list);
 
+extern set_show_commands add_setshow_enum_cmd
+  (const char *name, command_class theclass, const char *const *enumlist,
+   const char *set_doc, const char *show_doc,
+   const char *help_doc, setting_setter_ftype<const char *> set_func,
+   setting_getter_ftype<const char *> get_func, show_value_ftype *show_func,
+   cmd_list_element **set_list, cmd_list_element **show_list);
+
 extern set_show_commands add_setshow_auto_boolean_cmd
   (const char *name, command_class theclass, auto_boolean *var,
    const char *set_doc, const char *show_doc, const char *help_doc,
    cmd_func_ftype *set_func, show_value_ftype *show_func,
    cmd_list_element **set_list, cmd_list_element **show_list);
 
+extern set_show_commands add_setshow_auto_boolean_cmd
+  (const char *name, command_class theclass, const char *set_doc,
+   const char *show_doc, const char *help_doc,
+   setting_setter_ftype<enum auto_boolean> set_func,
+   setting_getter_ftype<enum auto_boolean> get_func,
+   show_value_ftype *show_func, cmd_list_element **set_list,
+   cmd_list_element **show_list);
+
 extern set_show_commands add_setshow_boolean_cmd
   (const char *name, command_class theclass, bool *var, const char *set_doc,
    const char *show_doc, const char *help_doc, cmd_func_ftype *set_func,
    show_value_ftype *show_func, cmd_list_element **set_list,
    cmd_list_element **show_list);
 
+extern set_show_commands add_setshow_boolean_cmd
+  (const char *name, command_class theclass, const char *set_doc,
+   const char *show_doc, const char *help_doc,
+   setting_setter_ftype<bool> set_func,
+   setting_getter_ftype<bool> get_func, show_value_ftype *show_func,
+   cmd_list_element **set_list, cmd_list_element **show_list);
+
 extern set_show_commands add_setshow_filename_cmd
-  (const char *name, command_class theclass, char **var, const char *set_doc,
+  (const char *name, command_class theclass, std::string *var, const char *set_doc,
+   const char *show_doc, const char *help_doc, cmd_func_ftype *set_func,
+   show_value_ftype *show_func, cmd_list_element **set_list,
+   cmd_list_element **show_list);
+
+extern set_show_commands add_setshow_filename_cmd
+  (const char *name, command_class theclass, const char *set_doc,
+   const char *show_doc, const char *help_doc,
+   setting_setter_ftype<std::string> set_func,
+   setting_getter_ftype<std::string> get_func, show_value_ftype *show_func,
+   cmd_list_element **set_list, cmd_list_element **show_list);
+
+extern set_show_commands add_setshow_string_cmd
+  (const char *name, command_class theclass, std::string *var, const char *set_doc,
    const char *show_doc, const char *help_doc, cmd_func_ftype *set_func,
    show_value_ftype *show_func, cmd_list_element **set_list,
    cmd_list_element **show_list);
 
 extern set_show_commands add_setshow_string_cmd
-  (const char *name, command_class theclass, char **var, const char *set_doc,
+  (const char *name, command_class theclass, const char *set_doc,
+   const char *show_doc, const char *help_doc,
+   setting_setter_ftype<std::string> set_func,
+   setting_getter_ftype<std::string> get_func,
+   show_value_ftype *show_func, cmd_list_element **set_list,
+   cmd_list_element **show_list);
+
+extern set_show_commands add_setshow_string_noescape_cmd
+  (const char *name, command_class theclass, std::string *var, const char *set_doc,
    const char *show_doc, const char *help_doc, cmd_func_ftype *set_func,
    show_value_ftype *show_func, cmd_list_element **set_list,
    cmd_list_element **show_list);
 
 extern set_show_commands add_setshow_string_noescape_cmd
-  (const char *name, command_class theclass, char **var, const char *set_doc,
+  (const char *name, command_class theclass, const char *set_doc,
+   const char *show_doc, const char *help_doc,
+   setting_setter_ftype<std::string> set_func,
+   setting_getter_ftype<std::string> get_func, show_value_ftype *show_func,
+   cmd_list_element **set_list, cmd_list_element **show_list);
+
+extern set_show_commands add_setshow_optional_filename_cmd
+  (const char *name, command_class theclass, std::string *var, const char *set_doc,
    const char *show_doc, const char *help_doc, cmd_func_ftype *set_func,
    show_value_ftype *show_func, cmd_list_element **set_list,
    cmd_list_element **show_list);
 
 extern set_show_commands add_setshow_optional_filename_cmd
-  (const char *name, command_class theclass, char **var, const char *set_doc,
-   const char *show_doc, const char *help_doc, cmd_func_ftype *set_func,
+  (const char *name, command_class theclass, const char *set_doc,
+   const char *show_doc, const char *help_doc,
+   setting_setter_ftype<std::string> set_func,
+   setting_getter_ftype<std::string> get_func,
    show_value_ftype *show_func, cmd_list_element **set_list,
    cmd_list_element **show_list);
 
@@ -448,30 +699,65 @@ extern set_show_commands add_setshow_integer_cmd
    show_value_ftype *show_func, cmd_list_element **set_list,
    cmd_list_element **show_list);
 
+extern set_show_commands add_setshow_integer_cmd
+  (const char *name, command_class theclass, const char *set_doc,
+   const char *show_doc, const char *help_doc,
+   setting_setter_ftype<int> set_func,
+   setting_getter_ftype<int> get_func, show_value_ftype *show_func,
+   cmd_list_element **set_list, cmd_list_element **show_list);
+
 extern set_show_commands add_setshow_uinteger_cmd
   (const char *name, command_class theclass, unsigned int *var,
    const char *set_doc, const char *show_doc, const char *help_doc,
    cmd_func_ftype *set_func, show_value_ftype *show_func,
    cmd_list_element **set_list, cmd_list_element **show_list);
 
+extern set_show_commands add_setshow_uinteger_cmd
+  (const char *name, command_class theclass, const char *set_doc,
+   const char *show_doc, const char *help_doc,
+   setting_setter_ftype<unsigned int> set_func,
+   setting_getter_ftype<unsigned int> get_func, show_value_ftype *show_func,
+   cmd_list_element **set_list, cmd_list_element **show_list);
+
 extern set_show_commands add_setshow_zinteger_cmd
   (const char *name, command_class theclass, int *var, const char *set_doc,
    const char *show_doc, const char *help_doc, cmd_func_ftype *set_func,
    show_value_ftype *show_func, cmd_list_element **set_list,
    cmd_list_element **show_list);
 
+extern set_show_commands add_setshow_zinteger_cmd
+  (const char *name, command_class theclass, const char *set_doc,
+   const char *show_doc, const char *help_doc,
+   setting_setter_ftype<int> set_func,
+   setting_getter_ftype<int> get_func, show_value_ftype *show_func,
+   cmd_list_element **set_list, cmd_list_element **show_list);
+
 extern set_show_commands add_setshow_zuinteger_cmd
   (const char *name, command_class theclass, unsigned int *var,
    const char *set_doc, const char *show_doc, const char *help_doc,
    cmd_func_ftype *set_func, show_value_ftype *show_func,
    cmd_list_element **set_list, cmd_list_element **show_list);
 
+extern set_show_commands add_setshow_zuinteger_cmd
+  (const char *name, command_class theclass, const char *set_doc,
+   const char *show_doc, const char *help_doc,
+   setting_setter_ftype<unsigned int> set_func,
+   setting_getter_ftype<unsigned int> get_func, show_value_ftype *show_func,
+   cmd_list_element **set_list, cmd_list_element **show_list);
+
 extern set_show_commands add_setshow_zuinteger_unlimited_cmd
   (const char *name, command_class theclass, int *var, const char *set_doc,
    const char *show_doc, const char *help_doc, cmd_func_ftype *set_func,
    show_value_ftype *show_func, cmd_list_element **set_list,
    cmd_list_element **show_list);
 
+extern set_show_commands add_setshow_zuinteger_unlimited_cmd
+  (const char *name, command_class theclass, const char *set_doc,
+   const char *show_doc, const char *help_doc,
+   setting_setter_ftype<int> set_func, setting_getter_ftype<int> get_func,
+   show_value_ftype *show_func, cmd_list_element **set_list,
+   cmd_list_element **show_list);
+
 /* Do a "show" command for each thing on a command list.  */
 
 extern void cmd_show_list (struct cmd_list_element *, int);

gdb/compile/compile.c

@@ -495,7 +495,22 @@ get_expr_block_and_pc (CORE_ADDR *pc)
 }
 
 /* String for 'set compile-args' and 'show compile-args'.  */
-static char *compile_args;
+static std::string compile_args =
+  /* Override flags possibly coming from DW_AT_producer.  */
+  "-O0 -gdwarf-4"
+  /* We use -fPIE Otherwise GDB would need to reserve space large enough for
+     any object file in the inferior in advance to get the final address when
+     to link the object file to and additionally the default system linker
+     script would need to be modified so that one can specify there the
+     absolute target address.
+     -fPIC is not used at is would require from GDB to generate .got.  */
+  " -fPIE"
+  /* We want warnings, except for some commonly happening for GDB commands.  */
+  " -Wall "
+  " -Wno-unused-but-set-variable"
+  " -Wno-unused-variable"
+  /* Override CU's possible -fstack-protector-strong.  */
+  " -fno-stack-protector";
 
 /* Parsed form of COMPILE_ARGS.  */
 static gdb_argv compile_args_argv;
@@ -505,7 +520,7 @@ static gdb_argv compile_args_argv;
 static void
 set_compile_args (const char *args, int from_tty, struct cmd_list_element *c)
 {
-  compile_args_argv = gdb_argv (compile_args);
+  compile_args_argv = gdb_argv (compile_args.c_str ());
 }
 
 /* Implement 'show compile-args'.  */
@@ -520,7 +535,7 @@ show_compile_args (struct ui_file *file, int from_tty,
 }
 
 /* String for 'set compile-gcc' and 'show compile-gcc'.  */
-static char *compile_gcc;
+static std::string compile_gcc;
 
 /* Implement 'show compile-gcc'.  */
 
@@ -696,13 +711,13 @@ compile_to_object (struct command_line *cmd, const char *cmd_string,
 
   compiler->set_verbose (compile_debug);
 
-  if (compile_gcc[0] != 0)
+  if (!compile_gcc.empty ())
     {
       if (compiler->version () < GCC_FE_VERSION_1)
 	error (_("Command 'set compile-gcc' requires GCC version 6 or higher "
 		 "(libcc1 interface version 1 or higher)"));
 
-      compiler->set_driver_filename (compile_gcc);
+      compiler->set_driver_filename (compile_gcc.c_str ());
     }
   else
     {
@@ -1029,23 +1044,9 @@ String quoting is parsed like in shell, for example:\n\
   -mno-align-double \"-I/dir with a space/include\""),
 			  set_compile_args, show_compile_args, &setlist, &showlist);
 
-  /* Override flags possibly coming from DW_AT_producer.  */
-  compile_args = xstrdup ("-O0 -gdwarf-4"
-  /* We use -fPIE Otherwise GDB would need to reserve space large enough for
-     any object file in the inferior in advance to get the final address when
-     to link the object file to and additionally the default system linker
-     script would need to be modified so that one can specify there the
-     absolute target address.
-     -fPIC is not used at is would require from GDB to generate .got.  */
-			 " -fPIE"
-  /* We want warnings, except for some commonly happening for GDB commands.  */
-			 " -Wall "
-			 " -Wno-unused-but-set-variable"
-			 " -Wno-unused-variable"
-  /* Override CU's possible -fstack-protector-strong.  */
-			 " -fno-stack-protector"
-  );
-  set_compile_args (compile_args, 0, NULL);
+
+  /* Initialize compile_args_argv.  */
+  set_compile_args (compile_args.c_str (), 0, NULL);
 
   add_setshow_optional_filename_cmd ("compile-gcc", class_support,
 				     &compile_gcc,
@@ -1058,5 +1059,4 @@ It should be absolute filename of the gcc executable.\n\
 If empty the default target triplet will be searched in $PATH."),
 				     NULL, show_compile_gcc, &setlist,
 				     &showlist);
-  compile_gcc = xstrdup ("");
 }

gdb/corefile.c

@@ -395,7 +395,7 @@ write_memory_signed_integer (CORE_ADDR addr, int len,
 const char *gnutarget;
 
 /* Same thing, except it is "auto" not NULL for the default case.  */
-static char *gnutarget_string;
+static std::string gnutarget_string;
 static void
 show_gnutarget_string (struct ui_file *file, int from_tty,
 		       struct cmd_list_element *c,
@@ -409,15 +409,15 @@ static void
 set_gnutarget_command (const char *ignore, int from_tty,
 		       struct cmd_list_element *c)
 {
-  char *gend = gnutarget_string + strlen (gnutarget_string);
+  const char *gend = gnutarget_string.c_str () + gnutarget_string.size ();
+  gend = remove_trailing_whitespace (gnutarget_string.c_str (), gend);
+  gnutarget_string
+    = gnutarget_string.substr (0, gend - gnutarget_string.data ());
 
-  gend = remove_trailing_whitespace (gnutarget_string, gend);
-  *gend = '\0';
-
-  if (strcmp (gnutarget_string, "auto") == 0)
+  if (gnutarget_string == "auto")
     gnutarget = NULL;
   else
-    gnutarget = gnutarget_string;
+    gnutarget = gnutarget_string.c_str ();
 }
 
 /* A completion function for "set gnutarget".  */
@@ -449,8 +449,7 @@ complete_set_gnutarget (struct cmd_list_element *cmd,
 void
 set_gnutarget (const char *newtarget)
 {
-  xfree (gnutarget_string);
-  gnutarget_string = xstrdup (newtarget);
+  gnutarget_string = newtarget;
   set_gnutarget_command (NULL, 0, NULL);
 }
 

gdb/defs.h

@@ -121,7 +121,7 @@ using RequireLongest = gdb::Requires<gdb::Or<std::is_same<T, LONGEST>,
 extern int dbx_commands;
 
 /* * System root path, used to find libraries etc.  */
-extern char *gdb_sysroot;
+extern std::string gdb_sysroot;
 
 /* * GDB datadir, used to store data files.  */
 extern std::string gdb_datadir;
@@ -131,7 +131,7 @@ extern std::string gdb_datadir;
 extern std::string python_libdir;
 
 /* * Search path for separate debug files.  */
-extern char *debug_file_directory;
+extern std::string debug_file_directory;
 
 /* GDB's SIGINT handler basically sets a flag; code that might take a
    long time before it gets back to the event loop, and which ought to

gdb/disasm.c

@@ -39,7 +39,7 @@
 
 /* This variable is used to hold the prospective disassembler_options value
    which is set by the "set disassembler_options" command.  */
-static char *prospective_options = NULL;
+static std::string prospective_options;
 
 /* This structure is used to store line number information for the
    deprecated /m option.
@@ -928,13 +928,16 @@ get_disassembler_options (struct gdbarch *gdbarch)
 }
 
 void
-set_disassembler_options (char *prospective_options)
+set_disassembler_options (const char *prospective_options)
 {
   struct gdbarch *gdbarch = get_current_arch ();
   char **disassembler_options = gdbarch_disassembler_options (gdbarch);
   const disasm_options_and_args_t *valid_options_and_args;
   const disasm_options_t *valid_options;
-  char *options = remove_whitespace_and_extra_commas (prospective_options);
+  gdb::unique_xmalloc_ptr<char> prospective_options_local
+    = make_unique_xstrdup (prospective_options);
+  char *options = remove_whitespace_and_extra_commas
+    (prospective_options_local.get ());
   const char *opt;
 
   /* Allow all architectures, even ones that do not support 'set disassembler',
@@ -1003,7 +1006,7 @@ static void
 set_disassembler_options_sfunc (const char *args, int from_tty,
 				struct cmd_list_element *c)
 {
-  set_disassembler_options (prospective_options);
+  set_disassembler_options (prospective_options.c_str ());
 }
 
 static void

gdb/disasm.h

@@ -164,6 +164,6 @@ extern char *get_disassembler_options (struct gdbarch *gdbarch);
 
 /* Sets the active gdbarch's disassembler options to OPTIONS.  */
 
-extern void set_disassembler_options (char *options);
+extern void set_disassembler_options (const char *options);
 
 #endif

gdb/dwarf2/dwz.c

@@ -118,7 +118,7 @@ dwz_search_other_debugdirs (std::string &filename, bfd_byte *buildid,
 
   gdb_bfd_ref_ptr dwz_bfd;
   std::vector<gdb::unique_xmalloc_ptr<char>> debugdir_vec
-    = dirnames_to_char_ptr_vec (debug_file_directory);
+    = dirnames_to_char_ptr_vec (debug_file_directory.c_str ());
 
   for (const gdb::unique_xmalloc_ptr<char> &debugdir : debugdir_vec)
     {

gdb/dwarf2/index-cache.c

@@ -37,7 +37,7 @@
 static bool debug_index_cache = false;
 
 /* The index cache directory, used for "set/show index-cache directory".  */
-static char *index_cache_directory = NULL;
+static std::string index_cache_directory;
 
 /* See dwarf-index.cache.h.  */
 index_cache global_index_cache;
@@ -290,9 +290,9 @@ set_index_cache_directory_command (const char *arg, int from_tty,
 				   cmd_list_element *element)
 {
   /* Make sure the index cache directory is absolute and tilde-expanded.  */
-  gdb::unique_xmalloc_ptr<char> abs (gdb_abspath (index_cache_directory));
-  xfree (index_cache_directory);
-  index_cache_directory = abs.release ();
+  gdb::unique_xmalloc_ptr<char> abs
+    = gdb_abspath (index_cache_directory.c_str ());
+  index_cache_directory = abs.get ();
   global_index_cache.set_directory (index_cache_directory);
 }
 
@@ -325,7 +325,7 @@ _initialize_index_cache ()
   std::string cache_dir = get_standard_cache_dir ();
   if (!cache_dir.empty ())
     {
-      index_cache_directory = xstrdup (cache_dir.c_str ());
+      index_cache_directory = cache_dir;
       global_index_cache.set_directory (std::move (cache_dir));
     }
   else

gdb/dwarf2/read.c

@@ -12047,10 +12047,10 @@ try_open_dwop_file (dwarf2_per_objfile *per_objfile,
   gdb::unique_xmalloc_ptr<char> search_path_holder;
   if (search_cwd)
     {
-      if (*debug_file_directory != '\0')
+      if (!debug_file_directory.empty ())
 	{
 	  search_path_holder.reset (concat (".", dirname_separator_string,
-					    debug_file_directory,
+					    debug_file_directory.c_str (),
 					    (char *) NULL));
 	  search_path = search_path_holder.get ();
 	}
@@ -12058,7 +12058,7 @@ try_open_dwop_file (dwarf2_per_objfile *per_objfile,
 	search_path = ".";
     }
   else
-    search_path = debug_file_directory;
+    search_path = debug_file_directory.c_str ();
 
   /* Add the path for the executable binary to the list of search paths.  */
   std::string objfile_dir = ldirname (objfile_name (per_objfile->objfile));
@@ -12129,7 +12129,7 @@ open_dwo_file (dwarf2_per_objfile *per_objfile,
   /* That didn't work, try debug-file-directory, which, despite its name,
      is a list of paths.  */
 
-  if (*debug_file_directory == '\0')
+  if (debug_file_directory.empty ())
     return NULL;
 
   return try_open_dwop_file (per_objfile, file_name,
@@ -12458,7 +12458,7 @@ open_dwp_file (dwarf2_per_objfile *per_objfile, const char *file_name)
      [IWBN if the dwp file name was recorded in the executable, akin to
      .gnu_debuglink, but that doesn't exist yet.]
      Strip the directory from FILE_NAME and search again.  */
-  if (*debug_file_directory != '\0')
+  if (!debug_file_directory.empty ())
     {
       /* Don't implicitly search the current directory here.
 	 If the user wants to search "." to handle this case,

gdb/event-top.c

@@ -461,13 +461,11 @@ display_gdb_prompt (const char *new_prompt)
 static std::string
 top_level_prompt (void)
 {
-  char *prompt;
-
   /* Give observers a chance of changing the prompt.  E.g., the python
      `gdb.prompt_hook' is installed as an observer.  */
-  gdb::observers::before_prompt.notify (get_prompt ());
+  gdb::observers::before_prompt.notify (get_prompt ().c_str ());
 
-  prompt = get_prompt ();
+  const std::string &prompt = get_prompt ();
 
   if (annotation_level >= 2)
     {
@@ -478,7 +476,7 @@ top_level_prompt (void)
 	 beginning.  */
       const char suffix[] = "\n\032\032prompt\n";
 
-      return std::string (prefix) + prompt + suffix;
+      return std::string (prefix) + prompt.c_str () + suffix;
     }
 
   return prompt;
@@ -1286,13 +1284,13 @@ handle_sigtstp (int sig)
 static void
 async_sigtstp_handler (gdb_client_data arg)
 {
-  char *prompt = get_prompt ();
+  const std::string &prompt = get_prompt ();
 
   signal (SIGTSTP, SIG_DFL);
   unblock_signal (SIGTSTP);
   raise (SIGTSTP);
   signal (SIGTSTP, handle_sigtstp);
-  printf_unfiltered ("%s", prompt);
+  printf_unfiltered ("%s", prompt.c_str ());
   gdb_flush (gdb_stdout);
 
   /* Forget about any previous command -- null line now will do

gdb/fork-child.c

@@ -33,14 +33,14 @@
 /* The exec-wrapper, if any, that will be used when starting the
    inferior.  */
 
-static char *exec_wrapper = NULL;
+static std::string exec_wrapper;
 
 /* See gdbsupport/common-inferior.h.  */
 
 const char *
 get_exec_wrapper ()
 {
-  return exec_wrapper;
+  return !exec_wrapper.empty () ? exec_wrapper.c_str () : nullptr;
 }
 
 /* See nat/fork-inferior.h.  */
@@ -139,8 +139,7 @@ gdb_startup_inferior (pid_t pid, int num_traps)
 static void
 unset_exec_wrapper_command (const char *args, int from_tty)
 {
-  xfree (exec_wrapper);
-  exec_wrapper = NULL;
+  exec_wrapper.clear ();
 }
 
 static void

gdb/guile/scm-param.c

@@ -44,7 +44,7 @@ union pascm_variable
   unsigned int uintval;
 
   /* Hold a string, for the various string types.  */
-  char *stringval;
+  std::string *stringval;
 
   /* Hold a string, for enums.  */
   const char *cstringval;
@@ -57,10 +57,7 @@ union pascm_variable
    2) Call register-parameter! to add the parameter to gdb.
    It is done this way so that the constructor, make-parameter, doesn't have
    any side-effects.  This means that the smob needs to store everything
-   that was passed to make-parameter.
-
-   N.B. There is no free function for this smob.
-   All objects pointed to by this smob must live in GC space.  */
+   that was passed to make-parameter.  */
 
 struct param_smob
 {
@@ -113,6 +110,29 @@ struct param_smob
   SCM containing_scm;
 };
 
+/* Wraps a setting around an existing param_smob.  This abstraction
+   is used to manipulate the value in S->VALUE in a type safe manner using
+   the setting interface.
+
+   The lifetime of the param_smob must be at least as long as the lifetime of
+   the wrapper.  */
+struct setting_wrapper final : public setting
+{
+  explicit setting_wrapper (param_smob *s)
+    : setting (s->type, this->get_var_ptr (s))
+  {}
+
+private:
+  /* Get pointer to the setting's storage.  */
+  void *get_var_ptr (param_smob *s)
+  {
+    if (var_type_uses<std::string> (s->type))
+      return s->value.stringval;
+    else
+      return &s->value;
+  }
+};
+
 static const char param_smob_name[] = "gdb:parameter";
 
 /* The tag Guile knows the param smob by.  */
@@ -133,8 +153,8 @@ static SCM unlimited_keyword;
 
 static int pascm_is_valid (param_smob *);
 static const char *pascm_param_type_name (enum var_types type);
-static SCM pascm_param_value (enum var_types type, void *var,
-			      int arg_pos, const char *func_name);
+static SCM pascm_param_value (const setting &var, int arg_pos,
+			      const char *func_name);
 
 /* Administrivia for parameter smobs.  */
 
@@ -153,8 +173,7 @@ pascm_print_param_smob (SCM self, SCM port, scm_print_state *pstate)
 
   gdbscm_printf (port, " %s ", pascm_param_type_name (p_smob->type));
 
-  value = pascm_param_value (p_smob->type, &p_smob->value,
-			     GDBSCM_ARG_NONE, NULL);
+  value = pascm_param_value (setting_wrapper (p_smob), GDBSCM_ARG_NONE, NULL);
   scm_display (value, port);
 
   scm_puts (">", port);
@@ -409,14 +428,14 @@ add_setshow_generic (enum var_types param_type, enum command_class cmd_class,
 
     case var_string:
       commands = add_setshow_string_cmd (cmd_name, cmd_class,
-					 &self->value.stringval, set_doc,
+					 self->value.stringval, set_doc,
 					 show_doc, help_doc, set_func,
 					 show_func, set_list, show_list);
       break;
 
     case var_string_noescape:
       commands = add_setshow_string_noescape_cmd (cmd_name, cmd_class,
-						  &self->value.stringval,
+						  self->value.stringval,
 						  set_doc, show_doc, help_doc,
 						  set_func, show_func, set_list,
 						  show_list);
@@ -425,7 +444,7 @@ add_setshow_generic (enum var_types param_type, enum command_class cmd_class,
 
     case var_optional_filename:
       commands = add_setshow_optional_filename_cmd (cmd_name, cmd_class,
-						    &self->value.stringval,
+						    self->value.stringval,
 						    set_doc, show_doc, help_doc,
 						    set_func, show_func,
 						    set_list, show_list);
@@ -433,7 +452,7 @@ add_setshow_generic (enum var_types param_type, enum command_class cmd_class,
 
     case var_filename:
       commands = add_setshow_filename_cmd (cmd_name, cmd_class,
-					   &self->value.stringval, set_doc,
+					   self->value.stringval, set_doc,
 					   show_doc, help_doc, set_func,
 					   show_func, set_list, show_list);
       break;
@@ -444,7 +463,7 @@ add_setshow_generic (enum var_types param_type, enum command_class cmd_class,
 				       show_doc, help_doc, set_func, show_func,
 				       set_list, show_list);
       /* Initialize the value, just in case.  */
-      self->value.cstringval = self->enumeration[0];
+      setting_wrapper (self).set<const char *> (self->enumeration[0]);
       break;
 
     default:
@@ -563,34 +582,38 @@ pascm_param_type_name (enum var_types param_type)
 }
 
 /* Return the value of a gdb parameter as a Scheme value.
-   If TYPE is not supported, then a <gdb:exception> object is returned.  */
+   If the var_type of VAR is not supported, then a <gdb:exception> object is
+   returned.  */
 
 static SCM
-pascm_param_value (enum var_types type, void *var,
-		   int arg_pos, const char *func_name)
+pascm_param_value (const setting &var, int arg_pos, const char *func_name)
 {
   /* Note: We *could* support var_integer here in case someone is trying to get
      the value of a Python-created parameter (which is the only place that
      still supports var_integer).  To further discourage its use we do not.  */
 
-  switch (type)
+  switch (var.type ())
     {
     case var_string:
     case var_string_noescape:
     case var_optional_filename:
     case var_filename:
+      {
+	const std::string str = var.get<std::string> ();
+	return gdbscm_scm_from_host_string (str.c_str (), str.length ());
+      }
+
     case var_enum:
       {
-	const char *str = *(char **) var;
-
-	if (str == NULL)
+	const char *str = var.get<const char *> ();
+	if (str == nullptr)
 	  str = "";
 	return gdbscm_scm_from_host_string (str, strlen (str));
       }
 
     case var_boolean:
       {
-	if (* (bool *) var)
+	if (var.get<bool> ())
 	  return SCM_BOOL_T;
 	else
 	  return SCM_BOOL_F;
@@ -598,7 +621,7 @@ pascm_param_value (enum var_types type, void *var,
 
     case var_auto_boolean:
       {
-	enum auto_boolean ab = * (enum auto_boolean *) var;
+	enum auto_boolean ab = var.get<enum auto_boolean> ();
 
 	if (ab == AUTO_BOOLEAN_TRUE)
 	  return SCM_BOOL_T;
@@ -609,67 +632,62 @@ pascm_param_value (enum var_types type, void *var,
       }
 
     case var_zuinteger_unlimited:
-      if (* (int *) var == -1)
+      if (var.get<int> () == -1)
 	return unlimited_keyword;
-      gdb_assert (* (int *) var >= 0);
+      gdb_assert (var.get<int> () >= 0);
       /* Fall through.  */
     case var_zinteger:
-      return scm_from_int (* (int *) var);
+      return scm_from_int (var.get<int> ());
 
     case var_uinteger:
-      if (* (unsigned int *) var == UINT_MAX)
+      if (var.get<unsigned int> ()== UINT_MAX)
 	return unlimited_keyword;
       /* Fall through.  */
     case var_zuinteger:
-      return scm_from_uint (* (unsigned int *) var);
+      return scm_from_uint (var.get<unsigned int> ());
 
     default:
       break;
     }
 
   return gdbscm_make_out_of_range_error (func_name, arg_pos,
-					 scm_from_int (type),
+					 scm_from_int (var.type ()),
 					 _("program error: unhandled type"));
 }
 
-/* Set the value of a parameter of type TYPE in VAR from VALUE.
+/* Set the value of a parameter of type P_SMOB->TYPE in P_SMOB->VAR from VALUE.
    ENUMERATION is the list of enum values for enum parameters, otherwise NULL.
    Throws a Scheme exception if VALUE_SCM is invalid for TYPE.  */
 
 static void
-pascm_set_param_value_x (enum var_types type, union pascm_variable *var,
+pascm_set_param_value_x (param_smob *p_smob,
 			 const char * const *enumeration,
 			 SCM value, int arg_pos, const char *func_name)
 {
-  switch (type)
+  setting_wrapper var { p_smob };
+
+  switch (var.type ())
     {
     case var_string:
     case var_string_noescape:
     case var_optional_filename:
     case var_filename:
       SCM_ASSERT_TYPE (scm_is_string (value)
-		       || (type != var_filename
+		       || (var.type () != var_filename
 			   && gdbscm_is_false (value)),
 		       value, arg_pos, func_name,
 		       _("string or #f for non-PARAM_FILENAME parameters"));
       if (gdbscm_is_false (value))
-	{
-	  xfree (var->stringval);
-	  if (type == var_optional_filename)
-	    var->stringval = xstrdup ("");
-	  else
-	    var->stringval = NULL;
-	}
+	var.set<std::string> ("");
       else
 	{
 	  SCM exception;
 
 	  gdb::unique_xmalloc_ptr<char> string
-	    = gdbscm_scm_to_host_string (value, NULL, &exception);
-	  if (string == NULL)
+	    = gdbscm_scm_to_host_string (value, nullptr, &exception);
+	  if (string == nullptr)
 	    gdbscm_throw (exception);
-	  xfree (var->stringval);
-	  var->stringval = string.release ();
+	  var.set<std::string> (string.release ());
 	}
       break;
 
@@ -681,27 +699,27 @@ pascm_set_param_value_x (enum var_types type, union pascm_variable *var,
 	SCM_ASSERT_TYPE (scm_is_string (value), value, arg_pos, func_name,
 		       _("string"));
 	gdb::unique_xmalloc_ptr<char> str
-	  = gdbscm_scm_to_host_string (value, NULL, &exception);
-	if (str == NULL)
+	  = gdbscm_scm_to_host_string (value, nullptr, &exception);
+	if (str == nullptr)
 	  gdbscm_throw (exception);
 	for (i = 0; enumeration[i]; ++i)
 	  {
 	    if (strcmp (enumeration[i], str.get ()) == 0)
 	      break;
 	  }
-	if (enumeration[i] == NULL)
+	if (enumeration[i] == nullptr)
 	  {
 	    gdbscm_out_of_range_error (func_name, arg_pos, value,
 				       _("not member of enumeration"));
 	  }
-	var->cstringval = enumeration[i];
+	var.set<const char *> (enumeration[i]);
 	break;
       }
 
     case var_boolean:
       SCM_ASSERT_TYPE (gdbscm_is_bool (value), value, arg_pos, func_name,
 		       _("boolean"));
-      var->boolval = gdbscm_is_true (value);
+      var.set<bool> (gdbscm_is_true (value));
       break;
 
     case var_auto_boolean:
@@ -710,19 +728,19 @@ pascm_set_param_value_x (enum var_types type, union pascm_variable *var,
 		       value, arg_pos, func_name,
 		       _("boolean or #:auto"));
       if (scm_is_eq (value, auto_keyword))
-	var->autoboolval = AUTO_BOOLEAN_AUTO;
+	var.set<enum auto_boolean> (AUTO_BOOLEAN_AUTO);
       else if (gdbscm_is_true (value))
-	var->autoboolval = AUTO_BOOLEAN_TRUE;
+	var.set<enum auto_boolean> (AUTO_BOOLEAN_TRUE);
       else
-	var->autoboolval = AUTO_BOOLEAN_FALSE;
+	var.set<enum auto_boolean> (AUTO_BOOLEAN_FALSE);
       break;
 
     case var_zinteger:
     case var_uinteger:
     case var_zuinteger:
     case var_zuinteger_unlimited:
-      if (type == var_uinteger
-	  || type == var_zuinteger_unlimited)
+      if (var.type () == var_uinteger
+	  || var.type () == var_zuinteger_unlimited)
 	{
 	  SCM_ASSERT_TYPE (gdbscm_is_bool (value)
 			   || scm_is_eq (value, unlimited_keyword),
@@ -730,10 +748,10 @@ pascm_set_param_value_x (enum var_types type, union pascm_variable *var,
 			   _("integer or #:unlimited"));
 	  if (scm_is_eq (value, unlimited_keyword))
 	    {
-	      if (type == var_uinteger)
-		var->intval = UINT_MAX;
+	      if (var.type () == var_uinteger)
+		var.set<unsigned int> (UINT_MAX);
 	      else
-		var->intval = -1;
+		var.set<int> (-1);
 	      break;
 	    }
 	}
@@ -743,25 +761,25 @@ pascm_set_param_value_x (enum var_types type, union pascm_variable *var,
 			   _("integer"));
 	}
 
-      if (type == var_uinteger
-	  || type == var_zuinteger)
+      if (var.type () == var_uinteger
+	  || var.type () == var_zuinteger)
 	{
 	  unsigned int u = scm_to_uint (value);
 
-	  if (type == var_uinteger && u == 0)
+	  if (var.type () == var_uinteger && u == 0)
 	    u = UINT_MAX;
-	  var->uintval = u;
+	  var.set<unsigned int> (u);
 	}
       else
 	{
 	  int i = scm_to_int (value);
 
-	  if (type == var_zuinteger_unlimited && i < -1)
+	  if (var.type () == var_zuinteger_unlimited && i < -1)
 	    {
 	      gdbscm_out_of_range_error (func_name, arg_pos, value,
 					 _("must be >= -1"));
 	    }
-	  var->intval = i;
+	  var.set<int> (i);
 	}
       break;
 
@@ -769,6 +787,21 @@ pascm_set_param_value_x (enum var_types type, union pascm_variable *var,
       gdb_assert_not_reached ("bad parameter type");
     }
 }
+
+/* Free function for a param_smob.  */
+static size_t
+pascm_free_parameter_smob (SCM self)
+{
+  param_smob *p_smob = (param_smob *) SCM_SMOB_DATA (self);
+
+  if (var_type_uses<std::string> (p_smob->type))
+    {
+      delete p_smob->value.stringval;
+      p_smob->value.stringval = nullptr;
+    }
+
+  return 0;
+}
 
 /* Parameter Scheme functions.  */
 
@@ -925,6 +958,10 @@ gdbscm_make_parameter (SCM name_scm, SCM rest)
   p_smob->set_func = set_func;
   p_smob->show_func = show_func;
 
+  scm_set_smob_free (parameter_smob_tag, pascm_free_parameter_smob);
+  if (var_type_uses<std::string> (p_smob->type))
+    p_smob->value.stringval = new std::string;
+
   if (initial_value_arg_pos > 0)
     {
       if (gdbscm_is_procedure (initial_value_scm))
@@ -934,7 +971,7 @@ gdbscm_make_parameter (SCM name_scm, SCM rest)
 	  if (gdbscm_is_exception (initial_value_scm))
 	    gdbscm_throw (initial_value_scm);
 	}
-      pascm_set_param_value_x (p_smob->type, &p_smob->value, enum_list,
+      pascm_set_param_value_x (p_smob, enum_list,
 			       initial_value_scm,
 			       initial_value_arg_pos, FUNC_NAME);
     }
@@ -1030,8 +1067,7 @@ gdbscm_parameter_value (SCM self)
       param_smob *p_smob = pascm_get_param_smob_arg_unsafe (self, SCM_ARG1,
 							    FUNC_NAME);
 
-      return pascm_param_value (p_smob->type, &p_smob->value,
-				SCM_ARG1, FUNC_NAME);
+      return pascm_param_value (setting_wrapper (p_smob), SCM_ARG1, FUNC_NAME);
     }
   else
     {
@@ -1062,13 +1098,14 @@ gdbscm_parameter_value (SCM self)
 	  gdbscm_out_of_range_error (FUNC_NAME, SCM_ARG1, self,
 				     _("parameter not found"));
 	}
-      if (cmd->var == NULL)
+
+      if (!cmd->var.has_value ())
 	{
 	  gdbscm_out_of_range_error (FUNC_NAME, SCM_ARG1, self,
 				     _("not a parameter"));
 	}
 
-      return pascm_param_value (cmd->var_type, cmd->var, SCM_ARG1, FUNC_NAME);
+      return pascm_param_value (*cmd->var, SCM_ARG1, FUNC_NAME);
     }
 }
 
@@ -1080,7 +1117,7 @@ gdbscm_set_parameter_value_x (SCM self, SCM value)
   param_smob *p_smob = pascm_get_param_smob_arg_unsafe (self, SCM_ARG1,
 							FUNC_NAME);
 
-  pascm_set_param_value_x (p_smob->type, &p_smob->value, p_smob->enumeration,
+  pascm_set_param_value_x (p_smob, p_smob->enumeration,
 			   value, SCM_ARG2, FUNC_NAME);
 
   return SCM_UNSPECIFIED;

gdb/infcmd.c

@@ -71,16 +71,16 @@ static void step_1 (int, int, const char *);
    Arguments are separated by spaces.  Empty string (pointer to '\0')
    means no args.  */
 
-static char *inferior_args_scratch;
+static std::string inferior_args_scratch;
 
 /* Scratch area where the new cwd will be stored by 'set cwd'.  */
 
-static char *inferior_cwd_scratch;
+static std::string inferior_cwd_scratch;
 
 /* Scratch area where 'set inferior-tty' will store user-provided value.
    We'll immediate copy it into per-inferior storage.  */
 
-static char *inferior_io_terminal_scratch;
+static std::string inferior_io_terminal_scratch;
 
 /* Pid of our debugged inferior, or 0 if no inferior now.
    Since various parts of infrun.c test this to see whether there is a program
@@ -2021,7 +2021,6 @@ path_info (const char *args, int from_tty)
 static void
 path_command (const char *dirname, int from_tty)
 {
-  char *exec_path;
   const char *env;
 
   dont_repeat ();
@@ -2029,10 +2028,9 @@ path_command (const char *dirname, int from_tty)
   /* Can be null if path is not set.  */
   if (!env)
     env = "";
-  exec_path = xstrdup (env);
-  mod_path (dirname, &exec_path);
-  current_inferior ()->environment.set (path_var_name, exec_path);
-  xfree (exec_path);
+  std::string exec_path = env;
+  mod_path (dirname, exec_path);
+  current_inferior ()->environment.set (path_var_name, exec_path.c_str ());
   if (from_tty)
     path_info (NULL, from_tty);
 }

gdb/linux-thread-db.c

@@ -110,7 +110,7 @@ public:
   gdb::byte_vector thread_info_to_thread_handle (struct thread_info *) override;
 };
 
-static char *libthread_db_search_path;
+static std::string libthread_db_search_path = LIBTHREAD_DB_SEARCH_PATH;
 
 /* Set to true if thread_db auto-loading is enabled
    by the "set auto-load libthread-db" command.  */
@@ -135,11 +135,8 @@ static void
 set_libthread_db_search_path (const char *ignored, int from_tty,
 			      struct cmd_list_element *c)
 {
-  if (*libthread_db_search_path == '\0')
-    {
-      xfree (libthread_db_search_path);
-      libthread_db_search_path = xstrdup (LIBTHREAD_DB_SEARCH_PATH);
-    }
+  if (libthread_db_search_path.empty ())
+    libthread_db_search_path = LIBTHREAD_DB_SEARCH_PATH;
 }
 
 /* If non-zero, print details of libthread_db processing.  */
@@ -942,7 +939,7 @@ try_thread_db_load_1 (struct thread_db_info *info)
 
   printf_unfiltered (_("[Thread debugging using libthread_db enabled]\n"));
 
-  if (*libthread_db_search_path || libthread_db_debug)
+  if (!libthread_db_search_path.empty () || libthread_db_debug)
     {
       struct ui_file *file;
       const char *library;
@@ -955,7 +952,7 @@ try_thread_db_load_1 (struct thread_db_info *info)
 	 disabled, still print it to gdb_stdout if debug output is
 	 enabled.  User visible output should not depend on debug
 	 settings.  */
-      file = *libthread_db_search_path != '\0' ? gdb_stdout : gdb_stdlog;
+      file = !libthread_db_search_path.empty () ? gdb_stdout : gdb_stdlog;
       fprintf_unfiltered (file,
 			  _("Using host libthread_db library \"%ps\".\n"),
 			  styled_string (file_name_style.style (), library));
@@ -1143,7 +1140,7 @@ thread_db_load_search (void)
   bool rc = false;
 
   std::vector<gdb::unique_xmalloc_ptr<char>> dir_vec
-    = dirnames_to_char_ptr_vec (libthread_db_search_path);
+    = dirnames_to_char_ptr_vec (libthread_db_search_path.c_str ());
 
   for (const gdb::unique_xmalloc_ptr<char> &this_dir_up : dir_vec)
     {
@@ -2006,8 +2003,6 @@ _initialize_thread_db ()
      and until there is a running inferior, we can't tell which
      libthread_db is the correct one to load.  */
 
-  libthread_db_search_path = xstrdup (LIBTHREAD_DB_SEARCH_PATH);
-
   add_setshow_optional_filename_cmd ("libthread-db-search-path",
 				     class_support,
 				     &libthread_db_search_path, _("\

gdb/main.c

@@ -65,7 +65,7 @@ char *interpreter_p;
 int dbx_commands = 0;
 
 /* System root path, used to find libraries etc.  */
-char *gdb_sysroot = 0;
+std::string gdb_sysroot;
 
 /* GDB datadir, used to store data files.  */
 std::string gdb_datadir;
@@ -710,19 +710,14 @@ captured_main_1 (struct captured_main_args *context)
     perror_warning_with_name (_("error finding working directory"));
 
   /* Set the sysroot path.  */
-  gdb_sysroot
-    = xstrdup (relocate_gdb_directory (TARGET_SYSTEM_ROOT,
-				     TARGET_SYSTEM_ROOT_RELOCATABLE).c_str ());
+  gdb_sysroot = relocate_gdb_directory (TARGET_SYSTEM_ROOT,
+					TARGET_SYSTEM_ROOT_RELOCATABLE);
 
-  if (*gdb_sysroot == '\0')
-    {
-      xfree (gdb_sysroot);
-      gdb_sysroot = xstrdup (TARGET_SYSROOT_PREFIX);
-    }
+  if (gdb_sysroot.empty ())
+    gdb_sysroot = TARGET_SYSROOT_PREFIX;
 
   debug_file_directory
-    = xstrdup (relocate_gdb_directory (DEBUGDIR,
-				     DEBUGDIR_RELOCATABLE).c_str ());
+    = relocate_gdb_directory (DEBUGDIR, DEBUGDIR_RELOCATABLE);
 
   gdb_datadir = relocate_gdb_directory (GDB_DATADIR,
 					GDB_DATADIR_RELOCATABLE);

gdb/maint-test-options.c

@@ -133,17 +133,12 @@ struct test_options_opts
   const char *enum_opt = test_options_enum_values_xxx;
   unsigned int uint_opt = 0;
   int zuint_unl_opt = 0;
-  char *string_opt = nullptr;
+  std::string string_opt;
 
   test_options_opts () = default;
 
   DISABLE_COPY_AND_ASSIGN (test_options_opts);
 
-  ~test_options_opts ()
-  {
-    xfree (string_opt);
-  }
-
   /* Dump the options to FILE.  ARGS is the remainder unprocessed
      arguments.  */
   void dump (ui_file *file, const char *args) const
@@ -162,9 +157,7 @@ struct test_options_opts
 			(zuint_unl_opt == -1
 			 ? "unlimited"
 			 : plongest (zuint_unl_opt)),
-			(string_opt != nullptr
-			 ? string_opt
-			 : ""),
+			string_opt.c_str (),
 			args);
   }
 };

gdb/maint-test-settings.c

@@ -44,13 +44,13 @@ static unsigned int maintenance_test_settings_zuinteger;
 
 static int maintenance_test_settings_zuinteger_unlimited;
 
-static char *maintenance_test_settings_string;
+static std::string maintenance_test_settings_string;
 
-static char *maintenance_test_settings_string_noescape;
+static std::string maintenance_test_settings_string_noescape;
 
-static char *maintenance_test_settings_optional_filename;
+static std::string maintenance_test_settings_optional_filename;
 
-static char *maintenance_test_settings_filename;
+static std::string maintenance_test_settings_filename;
 
 /* Enum values for the "maintenance set/show test-settings boolean"
    commands.  */

gdb/maint.c

@@ -1088,7 +1088,7 @@ set_per_command_cmd (const char *args, int from_tty)
     error (_("Bad value for 'mt set per-command no'."));
 
   for (list = per_command_setlist; list != NULL; list = list->next)
-    if (list->var_type == var_boolean)
+    if (list->var->type () == var_boolean)
       {
 	gdb_assert (list->type == set_cmd);
 	do_set_command (args, from_tty, list);

gdb/mi/mi-cmd-env.c

@@ -93,7 +93,7 @@ mi_cmd_env_cd (const char *command, char **argv, int argc)
 }
 
 static void
-env_mod_path (const char *dirname, char **which_path)
+env_mod_path (const char *dirname, std::string &which_path)
 {
   if (dirname == 0 || dirname[0] == '\0')
     return;
@@ -109,7 +109,6 @@ void
 mi_cmd_env_path (const char *command, char **argv, int argc)
 {
   struct ui_out *uiout = current_uiout;
-  char *exec_path;
   const char *env;
   int reset = 0;
   int oind = 0;
@@ -152,11 +151,11 @@ mi_cmd_env_path (const char *command, char **argv, int argc)
   argv += oind;
   argc -= oind;
 
-
+  std::string exec_path;
   if (reset)
     {
       /* Reset implies resetting to original path first.  */
-      exec_path = xstrdup (orig_path);
+      exec_path = orig_path;
     }
   else
     {
@@ -166,14 +165,14 @@ mi_cmd_env_path (const char *command, char **argv, int argc)
       /* Can be null if path is not set.  */
       if (!env)
 	env = "";
-      exec_path = xstrdup (env);
+
+      exec_path = env;
     }
 
   for (i = argc - 1; i >= 0; --i)
-    env_mod_path (argv[i], &exec_path);
+    env_mod_path (argv[i], exec_path);
 
-  current_inferior ()->environment.set (path_var_name, exec_path);
-  xfree (exec_path);
+  current_inferior ()->environment.set (path_var_name, exec_path.c_str ());
   env = current_inferior ()->environment.get (path_var_name);
   uiout->field_string ("path", env);
 }
@@ -228,12 +227,11 @@ mi_cmd_env_dir (const char *command, char **argv, int argc)
   if (reset)
     {
       /* Reset means setting to default path first.  */
-      xfree (source_path);
       init_source_path ();
     }
 
   for (i = argc - 1; i >= 0; --i)
-    env_mod_path (argv[i], &source_path);
+    env_mod_path (argv[i], source_path);
 
   uiout->field_string ("source-path", source_path);
   forget_cached_source_info ();

gdb/proc-api.c

@@ -50,14 +50,14 @@ struct trans {
 
 static bool  procfs_trace   = false;
 static FILE *procfs_file     = NULL;
-static char *procfs_filename;
+static std::string procfs_filename = "procfs_trace";
 
 static void
 prepare_to_trace (void)
 {
   if (procfs_trace)			/* if procfs tracing turned on */
     if (procfs_file == NULL)		/* if output file not yet open */
-      procfs_file = fopen (procfs_filename, "a");	/* open output file */
+      procfs_file = fopen (procfs_filename.c_str (), "a");	/* open output file */
 }
 
 static void
@@ -425,7 +425,6 @@ Show tracing for /proc api calls."), NULL,
 			   NULL, /* FIXME: i18n: */
 			   &setlist, &showlist);
 
-  procfs_filename = xstrdup ("procfs_trace");
   add_setshow_filename_cmd ("procfs-file", no_class, &procfs_filename, _("\
 Set filename for /proc tracefile."), _("\
 Show filename for /proc tracefile."), NULL,

gdb/python/py-param.c

@@ -64,8 +64,9 @@ union parmpy_variable
   /* Hold an unsigned integer value, for uinteger.  */
   unsigned int uintval;
 
-  /* Hold a string, for the various string types.  */
-  char *stringval;
+  /* Hold a string, for the various string types.  The std::string is
+     new-ed.  */
+  std::string *stringval;
 
   /* Hold a string, for enums.  */
   const char *cstringval;
@@ -88,6 +89,29 @@ struct parmpy_object
   const char **enumeration;
 };
 
+/* Wraps a setting around an existing parmpy_object.  This abstraction
+   is used to manipulate the value in S->VALUE in a type safe manner using
+   the setting interface.
+
+   The lifetime of the parmpy_object must be at least as long as the lifetime of
+   the wrapper.  */
+struct setting_wrapper final: setting
+{
+  explicit setting_wrapper (parmpy_object *s)
+    : setting (s->type, this->get_var_ptr (s))
+  {}
+
+private:
+  /* Get pointer to the setting's storage.  */
+  void *get_var_ptr (parmpy_object *s)
+  {
+    if (var_type_uses<std::string> (s->type))
+      return s->value.stringval;
+    else
+      return &s->value;
+  }
+};
+
 extern PyTypeObject parmpy_object_type
     CPYCHECKER_TYPE_OBJECT_FOR_TYPEDEF ("parmpy_object");
 
@@ -110,7 +134,8 @@ get_attr (PyObject *obj, PyObject *attr_name)
     {
       parmpy_object *self = (parmpy_object *) obj;
 
-      return gdbpy_parameter_value (self->type, &self->value);
+      setting_wrapper wrapper { self };
+      return gdbpy_parameter_value (wrapper);
     }
 
   return PyObject_GenericGetAttr (obj, attr_name);
@@ -139,13 +164,7 @@ set_parameter_value (parmpy_object *self, PyObject *value)
 	  return -1;
 	}
       if (value == Py_None)
-	{
-	  xfree (self->value.stringval);
-	  if (self->type == var_optional_filename)
-	    self->value.stringval = xstrdup ("");
-	  else
-	    self->value.stringval = NULL;
-	}
+	self->value.stringval->clear ();
       else
 	{
 	  gdb::unique_xmalloc_ptr<char>
@@ -153,8 +172,7 @@ set_parameter_value (parmpy_object *self, PyObject *value)
 	  if (string == NULL)
 	    return -1;
 
-	  xfree (self->value.stringval);
-	  self->value.stringval = string.release ();
+	  *self->value.stringval = string.get ();
 	}
       break;
 
@@ -501,14 +519,14 @@ add_setshow_generic (int parmclass, enum command_class cmdclass,
 
     case var_string:
       commands = add_setshow_string_cmd (cmd_name.get (), cmdclass,
-					 &self->value.stringval, set_doc,
+					 self->value.stringval, set_doc,
 					 show_doc, help_doc, get_set_value,
 					 get_show_value, set_list, show_list);
       break;
 
     case var_string_noescape:
       commands = add_setshow_string_noescape_cmd (cmd_name.get (), cmdclass,
-						  &self->value.stringval,
+						  self->value.stringval,
 						  set_doc, show_doc, help_doc,
 						  get_set_value, get_show_value,
 						  set_list, show_list);
@@ -516,7 +534,7 @@ add_setshow_generic (int parmclass, enum command_class cmdclass,
 
     case var_optional_filename:
       commands = add_setshow_optional_filename_cmd (cmd_name.get (), cmdclass,
-						    &self->value.stringval,
+						    self->value.stringval,
 						    set_doc, show_doc, help_doc,
 						    get_set_value,
 						    get_show_value, set_list,
@@ -525,7 +543,7 @@ add_setshow_generic (int parmclass, enum command_class cmdclass,
 
     case var_filename:
       commands = add_setshow_filename_cmd (cmd_name.get (), cmdclass,
-					   &self->value.stringval, set_doc,
+					   self->value.stringval, set_doc,
 					   show_doc, help_doc, get_set_value,
 					   get_show_value, set_list, show_list);
       break;
@@ -708,6 +726,9 @@ parmpy_init (PyObject *self, PyObject *args, PyObject *kwds)
   obj->type = (enum var_types) parmclass;
   memset (&obj->value, 0, sizeof (obj->value));
 
+  if (var_type_uses<std::string> (obj->type))
+    obj->value.stringval = new std::string;
+
   gdb::unique_xmalloc_ptr<char> cmd_name
     = gdbpy_parse_command_name (name, &set_list, &setlist);
   if (cmd_name == nullptr)
@@ -740,7 +761,16 @@ parmpy_init (PyObject *self, PyObject *args, PyObject *kwds)
   return 0;
 }
 
-
+/* Deallocate function for a gdb.Parameter.  */
+
+static void
+parmpy_dealloc (PyObject *obj)
+{
+  parmpy_object *parm_obj = (parmpy_object *) obj;
+
+  if (var_type_uses<std::string> (parm_obj->type))
+    delete parm_obj->value.stringval;
+}
 
 /* Initialize the 'parameters' module.  */
 int
@@ -779,7 +809,7 @@ PyTypeObject parmpy_object_type =
   "gdb.Parameter",		  /*tp_name*/
   sizeof (parmpy_object),	  /*tp_basicsize*/
   0,				  /*tp_itemsize*/
-  0,				  /*tp_dealloc*/
+  parmpy_dealloc,		  /*tp_dealloc*/
   0,				  /*tp_print*/
   0,				  /*tp_getattr*/
   0,				  /*tp_setattr*/

gdb/python/python-internal.h

@@ -438,7 +438,7 @@ PyObject *gdbpy_create_ptid_object (ptid_t ptid);
 PyObject *gdbpy_selected_thread (PyObject *self, PyObject *args);
 PyObject *gdbpy_selected_inferior (PyObject *self, PyObject *args);
 PyObject *gdbpy_string_to_argv (PyObject *self, PyObject *args);
-PyObject *gdbpy_parameter_value (enum var_types type, void *var);
+PyObject *gdbpy_parameter_value (const setting &var);
 gdb::unique_xmalloc_ptr<char> gdbpy_parse_command_name
   (const char *name, struct cmd_list_element ***base_list,
    struct cmd_list_element **start_list);

gdb/python/python.c

@@ -448,9 +448,9 @@ python_command (const char *arg, int from_tty)
    NULL (and set a Python exception) on error.  Helper function for
    get_parameter.  */
 PyObject *
-gdbpy_parameter_value (enum var_types type, void *var)
+gdbpy_parameter_value (const setting &var)
 {
-  switch (type)
+  switch (var.type ())
     {
     case var_string:
     case var_string_noescape:
@@ -458,16 +458,18 @@ gdbpy_parameter_value (enum var_types type, void *var)
     case var_filename:
     case var_enum:
       {
-	const char *str = *(char **) var;
+	std::string str;
+	if (var.type () == var_enum)
+	  str = var.get<const char *> ();
+	else
+	  str = var.get<std::string> ();
 
-	if (! str)
-	  str = "";
-	return host_string_to_python_string (str).release ();
+	return host_string_to_python_string (str.c_str ()).release ();
       }
 
     case var_boolean:
       {
-	if (* (bool *) var)
+	if (var.get<bool> ())
 	  Py_RETURN_TRUE;
 	else
 	  Py_RETURN_FALSE;
@@ -475,7 +477,7 @@ gdbpy_parameter_value (enum var_types type, void *var)
 
     case var_auto_boolean:
       {
-	enum auto_boolean ab = * (enum auto_boolean *) var;
+	enum auto_boolean ab = var.get<enum auto_boolean> ();
 
 	if (ab == AUTO_BOOLEAN_TRUE)
 	  Py_RETURN_TRUE;
@@ -486,16 +488,16 @@ gdbpy_parameter_value (enum var_types type, void *var)
       }
 
     case var_integer:
-      if ((* (int *) var) == INT_MAX)
+      if (var.get<int> () == INT_MAX)
 	Py_RETURN_NONE;
       /* Fall through.  */
     case var_zinteger:
     case var_zuinteger_unlimited:
-      return gdb_py_object_from_longest (* (int *) var).release ();
+      return gdb_py_object_from_longest (var.get<int> ()).release ();
 
     case var_uinteger:
       {
-	unsigned int val = * (unsigned int *) var;
+	unsigned int val = var.get<unsigned int> ();
 
 	if (val == UINT_MAX)
 	  Py_RETURN_NONE;
@@ -504,7 +506,7 @@ gdbpy_parameter_value (enum var_types type, void *var)
 
     case var_zuinteger:
       {
-	unsigned int val = * (unsigned int *) var;
+	unsigned int val = var.get<unsigned int> ();
 	return gdb_py_object_from_ulongest (val).release ();
       }
     }
@@ -541,10 +543,11 @@ gdbpy_parameter (PyObject *self, PyObject *args)
     return PyErr_Format (PyExc_RuntimeError,
 			 _("Could not find parameter `%s'."), arg);
 
-  if (! cmd->var)
+  if (!cmd->var.has_value ())
     return PyErr_Format (PyExc_RuntimeError,
 			 _("`%s' is not a parameter."), arg);
-  return gdbpy_parameter_value (cmd->var_type, cmd->var);
+
+  return gdbpy_parameter_value (*cmd->var);
 }
 
 /* Wrapper for target_charset.  */

gdb/remote-sim.c

@@ -680,10 +680,9 @@ gdbsim_target_open (const char *args, int from_tty)
   int len;
   char *arg_buf;
   struct sim_inferior_data *sim_data;
-  const char *sysroot;
   SIM_DESC gdbsim_desc;
 
-  sysroot = gdb_sysroot;
+  const std::string &sysroot = gdb_sysroot;
   if (is_target_filename (sysroot))
     sysroot += strlen (TARGET_SYSROOT_PREFIX);
 
@@ -704,7 +703,7 @@ gdbsim_target_open (const char *args, int from_tty)
   len = (7 + 1			/* gdbsim */
 	 + strlen (" -E little")
 	 + strlen (" --architecture=xxxxxxxxxx")
-	 + strlen (" --sysroot=") + strlen (sysroot) +
+	 + strlen (" --sysroot=") + sysroot.length () +
 	 + (args ? strlen (args) : 0)
 	 + 50) /* slack */ ;
   arg_buf = (char *) alloca (len);
@@ -731,7 +730,7 @@ gdbsim_target_open (const char *args, int from_tty)
     }
   /* Pass along gdb's concept of the sysroot.  */
   strcat (arg_buf, " --sysroot=");
-  strcat (arg_buf, sysroot);
+  strcat (arg_buf, sysroot.c_str ());
   /* finally, any explicit args */
   if (args)
     {

gdb/remote.c

@@ -1004,7 +1004,7 @@ static const struct program_space_key<char, gdb::xfree_deleter<char>>
    remote exec-file commands.  While the remote exec-file setting is
    per-program-space, the set/show machinery uses this as the 
    location of the remote exec-file value.  */
-static char *remote_exec_file_var;
+static std::string remote_exec_file_var;
 
 /* The size to align memory write packets, when practical.  The protocol
    does not guarantee any alignment, and gdb will generate short
@@ -1355,8 +1355,8 @@ static void
 set_remote_exec_file (const char *ignored, int from_tty,
 		      struct cmd_list_element *c)
 {
-  gdb_assert (remote_exec_file_var != NULL);
-  set_pspace_remote_exec_file (current_program_space, remote_exec_file_var);
+  set_pspace_remote_exec_file (current_program_space,
+			       remote_exec_file_var.c_str ());
 }
 
 /* The "set/show remote exec-file" show command hook.  */
@@ -2244,7 +2244,7 @@ show_remote_protocol_packet_cmd (struct ui_file *file, int from_tty,
        packet < &remote_protocol_packets[PACKET_MAX];
        packet++)
     {
-      if (&packet->detect == c->var)
+      if (&packet->detect == c->var->get_p<enum auto_boolean> ())
 	{
 	  show_packet_config_cmd (packet);
 	  return;
@@ -12618,7 +12618,7 @@ remote_target::filesystem_is_local ()
      this case we treat the remote filesystem as local if the
      sysroot is exactly TARGET_SYSROOT_PREFIX and if the stub
      does not support vFile:open.  */
-  if (strcmp (gdb_sysroot, TARGET_SYSROOT_PREFIX) == 0)
+  if (gdb_sysroot == TARGET_SYSROOT_PREFIX)
     {
       enum packet_support ps = packet_support (PACKET_vFile_open);
 
@@ -13246,7 +13246,7 @@ remote_target::download_tracepoint (struct bp_location *loc)
 		   "ignoring tp %d cond"), b->number);
     }
 
-  if (b->commands || *default_collect)
+  if (b->commands || !default_collect.empty ())
     {
       size_left = buf.size () - strlen (buf.data ());
 

gdb/serial.c

@@ -38,7 +38,7 @@ static struct serial *scb_base;
 /* Non-NULL gives filename which contains a recording of the remote session,
    suitable for playback by gdbserver.  */
 
-static char *serial_logfile = NULL;
+static std::string serial_logfile;
 static struct ui_file *serial_logfp = NULL;
 
 static const struct serial_ops *serial_interface_lookup (const char *);
@@ -251,12 +251,12 @@ serial_open_ops_1 (const struct serial_ops *ops, const char *open_name)
   scb->next = scb_base;
   scb_base = scb;
 
-  if (serial_logfile != NULL)
+  if (!serial_logfile.empty ())
     {
       stdio_file_up file (new stdio_file ());
 
-      if (!file->open (serial_logfile, "w"))
-	perror_with_name (serial_logfile);
+      if (!file->open (serial_logfile.c_str (), "w"))
+	perror_with_name (serial_logfile.c_str ());
 
       serial_logfp = file.release ();
     }

gdb/solib.c

@@ -98,7 +98,7 @@ struct target_so_ops *current_target_so_ops;
 /* If non-empty, this is a search path for loading non-absolute shared library
    symbol files.  This takes precedence over the environment variables PATH
    and LD_LIBRARY_PATH.  */
-static char *solib_search_path = NULL;
+static std::string solib_search_path;
 static void
 show_solib_search_path (struct ui_file *file, int from_tty,
 			struct cmd_list_element *c, const char *value)
@@ -157,7 +157,7 @@ solib_find_1 (const char *in_pathname, int *fd, bool is_solib)
   int found_file = -1;
   gdb::unique_xmalloc_ptr<char> temp_pathname;
   const char *fskind = effective_target_file_system_kind ();
-  const char *sysroot = gdb_sysroot;
+  const char *sysroot = gdb_sysroot.c_str ();
   int prefix_len, orig_prefix_len;
 
   /* If the absolute prefix starts with "target:" but the filesystem
@@ -321,8 +321,8 @@ solib_find_1 (const char *in_pathname, int *fd, bool is_solib)
 
   /* If not found, and we're looking for a solib, search the
      solib_search_path (if any).  */
-  if (is_solib && found_file < 0 && solib_search_path != NULL)
-    found_file = openp (solib_search_path,
+  if (is_solib && found_file < 0 && !solib_search_path.empty ())
+    found_file = openp (solib_search_path.c_str (),
 			OPF_TRY_CWD_FIRST | OPF_RETURN_REALPATH,
 			in_pathname, O_RDONLY | O_BINARY, &temp_pathname);
 
@@ -330,8 +330,8 @@ solib_find_1 (const char *in_pathname, int *fd, bool is_solib)
      solib_search_path (if any) for the basename only (ignoring the
      path).  This is to allow reading solibs from a path that differs
      from the opened path.  */
-  if (is_solib && found_file < 0 && solib_search_path != NULL)
-    found_file = openp (solib_search_path,
+  if (is_solib && found_file < 0 && !solib_search_path.empty ())
+    found_file = openp (solib_search_path.c_str (),
 			OPF_TRY_CWD_FIRST | OPF_RETURN_REALPATH,
 			target_lbasename (fskind, in_pathname),
 			O_RDONLY | O_BINARY, &temp_pathname);
@@ -380,7 +380,7 @@ exec_file_find (const char *in_pathname, int *fd)
   if (in_pathname == NULL)
     return NULL;
 
-  if (*gdb_sysroot != '\0' && IS_TARGET_ABSOLUTE_PATH (fskind, in_pathname))
+  if (!gdb_sysroot.empty () && IS_TARGET_ABSOLUTE_PATH (fskind, in_pathname))
     {
       result = solib_find_1 (in_pathname, fd, false);
 
@@ -1396,18 +1396,18 @@ gdb_sysroot_changed (const char *ignored, int from_tty,
   const char *old_prefix = "remote:";
   const char *new_prefix = TARGET_SYSROOT_PREFIX;
 
-  if (startswith (gdb_sysroot, old_prefix))
+  if (startswith (gdb_sysroot.c_str (), old_prefix))
     {
       static bool warning_issued = false;
 
       gdb_assert (strlen (old_prefix) == strlen (new_prefix));
-      memcpy (gdb_sysroot, new_prefix, strlen (new_prefix));
+      gdb_sysroot = new_prefix + gdb_sysroot.substr (strlen (old_prefix));
 
       if (!warning_issued)
 	{
 	  warning (_("\"%s\" is deprecated, use \"%s\" instead."),
 		   old_prefix, new_prefix);
-	  warning (_("sysroot set to \"%s\"."), gdb_sysroot);
+	  warning (_("sysroot set to \"%s\"."), gdb_sysroot.c_str ());
 
 	  warning_issued = true;
 	}

gdb/source.c

@@ -57,7 +57,7 @@
 /* Path of directories to search for source files.
    Same format as the PATH environment variable's value.  */
 
-char *source_path;
+std::string source_path;
 
 /* Support for source path substitution commands.  */
 
@@ -365,17 +365,15 @@ set_directories_command (const char *args,
 {
   /* This is the value that was set.
      It needs to be processed to maintain $cdir:$cwd and remove dups.  */
-  char *set_path = source_path;
+  std::string set_path = source_path;
 
   /* We preserve the invariant that $cdir:$cwd begins life at the end of
      the list by calling init_source_path.  If they appear earlier in
      SET_PATH then mod_path will move them appropriately.
      mod_path will also remove duplicates.  */
   init_source_path ();
-  if (*set_path != '\0')
-    mod_path (set_path, &source_path);
-
-  xfree (set_path);
+  if (!set_path.empty ())
+    mod_path (set_path.c_str (), source_path);
 }
 
 /* Print the list of source directories.
@@ -386,7 +384,7 @@ static void
 show_directories_1 (char *ignore, int from_tty)
 {
   puts_filtered ("Source directories searched: ");
-  puts_filtered (source_path);
+  puts_filtered (source_path.c_str ());
   puts_filtered ("\n");
 }
 
@@ -437,10 +435,7 @@ forget_cached_source_info (void)
 void
 init_source_path (void)
 {
-  char buf[20];
-
-  xsnprintf (buf, sizeof (buf), "$cdir%c$cwd", DIRNAME_SEPARATOR);
-  source_path = xstrdup (buf);
+  source_path = string_printf ("$cdir%c$cwd", DIRNAME_SEPARATOR);
   forget_cached_source_info ();
 }
 
@@ -456,20 +451,20 @@ directory_command (const char *dirname, int from_tty)
     {
       if (!from_tty || query (_("Reinitialize source path to empty? ")))
 	{
-	  xfree (source_path);
 	  init_source_path ();
 	  value_changed = true;
 	}
     }
   else
     {
-      mod_path (dirname, &source_path);
+      mod_path (dirname, source_path);
       forget_cached_source_info ();
       value_changed = true;
     }
   if (value_changed)
     {
-      gdb::observers::command_param_changed.notify ("directories", source_path);
+      gdb::observers::command_param_changed.notify ("directories",
+						    source_path.c_str ());
       if (from_tty)
 	show_directories_1 ((char *) 0, from_tty);
     }
@@ -481,13 +476,13 @@ directory_command (const char *dirname, int from_tty)
 void
 directory_switch (const char *dirname, int from_tty)
 {
-  add_path (dirname, &source_path, 0);
+  add_path (dirname, source_path, 0);
 }
 
 /* Add zero or more directories to the front of an arbitrary path.  */
 
 void
-mod_path (const char *dirname, char **which_path)
+mod_path (const char *dirname, std::string &which_path)
 {
   add_path (dirname, which_path, 1);
 }
@@ -675,6 +670,17 @@ add_path (const char *dirname, char **which_path, int parse_separators)
     }
 }
 
+/* add_path would need to be re-written to work on an std::string, but this is
+   not trivial.  Hence this overload which copies to a `char *` and back.  */
+
+void
+add_path (const char *dirname, std::string &which_path, int parse_separators)
+{
+  char *which_path_copy = xstrdup (which_path.data ());
+  add_path (dirname, &which_path_copy, parse_separators);
+  which_path = which_path_copy;
+  xfree (which_path_copy);
+}
 
 static void
 info_source_command (const char *ignore, int from_tty)
@@ -953,7 +959,7 @@ source_full_path_of (const char *filename,
 {
   int fd;
 
-  fd = openp (source_path,
+  fd = openp (source_path.c_str (),
 	      OPF_TRY_CWD_FIRST | OPF_SEARCH_IN_PATH | OPF_RETURN_REALPATH,
 	      filename, O_RDONLY, full_pathname);
   if (fd < 0)
@@ -1044,7 +1050,8 @@ find_and_open_source (const char *filename,
 		      const char *dirname,
 		      gdb::unique_xmalloc_ptr<char> *fullname)
 {
-  char *path = source_path;
+  const char *path = source_path.c_str ();
+  std::string expanded_path_holder;
   const char *p;
   int result;
 
@@ -1086,19 +1093,22 @@ find_and_open_source (const char *filename,
       /* Replace a path entry of $cdir with the compilation directory
 	 name.  */
 #define	cdir_len	5
-      p = strstr (source_path, "$cdir");
+      p = strstr (source_path.c_str (), "$cdir");
       if (p && (p == path || p[-1] == DIRNAME_SEPARATOR)
 	  && (p[cdir_len] == DIRNAME_SEPARATOR || p[cdir_len] == '\0'))
 	{
-	  int len;
+	  int len = p - source_path.c_str ();
 
-	  path = (char *)
-	    alloca (strlen (source_path) + 1 + strlen (dirname) + 1);
-	  len = p - source_path;
-	  strncpy (path, source_path, len);	/* Before $cdir */
-	  strcpy (path + len, dirname);		/* new stuff */
-	  strcat (path + len, source_path + len + cdir_len);	/* After
-								   $cdir */
+	  /* Before $cdir */
+	  expanded_path_holder = source_path.substr (0, len);
+
+	  /* new stuff */
+	  expanded_path_holder += dirname;
+
+	  /* After $cdir */
+	  expanded_path_holder += source_path.c_str () + len + cdir_len;
+
+	  path = expanded_path_holder.c_str ();
 	}
     }
 

gdb/source.h

@@ -39,13 +39,14 @@ extern int openp (const char *, openp_flags, const char *, int,
 
 extern int source_full_path_of (const char *, gdb::unique_xmalloc_ptr<char> *);
 
-extern void mod_path (const char *, char **);
+extern void mod_path (const char *, std::string &);
 
 extern void add_path (const char *, char **, int);
+extern void add_path (const char *, std::string &, int);
 
 extern void directory_switch (const char *, int);
 
-extern char *source_path;
+extern std::string source_path;
 
 extern void init_source_path (void);
 

gdb/stack.c

@@ -2424,12 +2424,7 @@ print_frame_local_vars (struct frame_info *frame,
 struct info_print_options
 {
   bool quiet = false;
-  char *type_regexp = nullptr;
-
-  ~info_print_options ()
-  {
-    xfree (type_regexp);
-  }
+  std::string type_regexp;
 };
 
 /* The options used by the 'info locals' and 'info args' commands.  */
@@ -2488,9 +2483,11 @@ info_locals_command (const char *args, int from_tty)
   if (args != nullptr && *args == '\0')
     args = nullptr;
 
-  print_frame_local_vars (get_selected_frame (_("No frame selected.")),
-			  opts.quiet, args, opts.type_regexp,
-			  0, gdb_stdout);
+  print_frame_local_vars
+    (get_selected_frame (_("No frame selected.")),
+     opts.quiet, args,
+     opts.type_regexp.empty () ? nullptr : opts.type_regexp.c_str (),
+     0, gdb_stdout);
 }
 
 /* Iterate over all the argument variables in block B.  */
@@ -2599,8 +2596,11 @@ info_args_command (const char *args, int from_tty)
   if (args != nullptr && *args == '\0')
     args = nullptr;
 
-  print_frame_arg_vars (get_selected_frame (_("No frame selected.")),
-			opts.quiet, args, opts.type_regexp, gdb_stdout);
+  print_frame_arg_vars
+    (get_selected_frame (_("No frame selected.")),
+     opts.quiet, args,
+     opts.type_regexp.empty () ? nullptr : opts.type_regexp.c_str (),
+     gdb_stdout);
 }
 
 /* Return the symbol-block in which the selected frame is executing.

gdb/symfile.c

@@ -1349,7 +1349,7 @@ separate_debug_file_exists (const std::string &name, unsigned long crc,
   return 1;
 }
 
-char *debug_file_directory = NULL;
+std::string debug_file_directory;
 static void
 show_debug_file_directory (struct ui_file *file, int from_tty,
 			   struct cmd_list_element *c, const char *value)
@@ -1406,8 +1406,9 @@ find_separate_debug_file (const char *dir,
   bool target_prefix = startswith (dir, "target:");
   const char *dir_notarget = target_prefix ? dir + strlen ("target:") : dir;
   std::vector<gdb::unique_xmalloc_ptr<char>> debugdir_vec
-    = dirnames_to_char_ptr_vec (debug_file_directory);
-  gdb::unique_xmalloc_ptr<char> canon_sysroot = gdb_realpath (gdb_sysroot);
+    = dirnames_to_char_ptr_vec (debug_file_directory.c_str ());
+  gdb::unique_xmalloc_ptr<char> canon_sysroot
+    = gdb_realpath (gdb_sysroot.c_str ());
 
  /* MS-Windows/MS-DOS don't allow colons in file names; we must
     convert the drive letter into a one-letter directory, so that the
@@ -1448,7 +1449,7 @@ find_separate_debug_file (const char *dir,
 	  if (canon_sysroot.get () != NULL)
 	    base_path = child_path (canon_sysroot.get (), canon_dir);
 	  else
-	    base_path = child_path (gdb_sysroot, canon_dir);
+	    base_path = child_path (gdb_sysroot.c_str (), canon_dir);
 	}
       if (base_path != NULL)
 	{
@@ -2654,7 +2655,7 @@ add_filename_language (const char *ext, enum language lang)
   filename_language_table.emplace_back (ext, lang);
 }
 
-static char *ext_args;
+static std::string ext_args;
 static void
 show_ext_args (struct ui_file *file, int from_tty,
 	       struct cmd_list_element *c, const char *value)
@@ -2669,48 +2670,48 @@ static void
 set_ext_lang_command (const char *args,
 		      int from_tty, struct cmd_list_element *e)
 {
-  char *cp = ext_args;
-  enum language lang;
+  const char *begin = ext_args.c_str ();
+  const char *end = ext_args.c_str ();
 
   /* First arg is filename extension, starting with '.'  */
-  if (*cp != '.')
-    error (_("'%s': Filename extension must begin with '.'"), ext_args);
+  if (*end != '.')
+    error (_("'%s': Filename extension must begin with '.'"), ext_args.c_str ());
 
   /* Find end of first arg.  */
-  while (*cp && !isspace (*cp))
-    cp++;
+  while (*end != '\0' && !isspace (*end))
+    end++;
 
-  if (*cp == '\0')
+  if (*end == '\0')
     error (_("'%s': two arguments required -- "
 	     "filename extension and language"),
-	   ext_args);
+	   ext_args.c_str ());
 
-  /* Null-terminate first arg.  */
-  *cp++ = '\0';
+  /* Extract first arg, the extension.  */
+  std::string extension = ext_args.substr (0, end - begin);
 
   /* Find beginning of second arg, which should be a source language.  */
-  cp = skip_spaces (cp);
+  begin = skip_spaces (end);
 
-  if (*cp == '\0')
+  if (*begin == '\0')
     error (_("'%s': two arguments required -- "
 	     "filename extension and language"),
-	   ext_args);
+	   ext_args.c_str ());
 
   /* Lookup the language from among those we know.  */
-  lang = language_enum (cp);
+  language lang = language_enum (begin);
 
   auto it = filename_language_table.begin ();
   /* Now lookup the filename extension: do we already know it?  */
   for (; it != filename_language_table.end (); it++)
     {
-      if (it->ext == ext_args)
+      if (it->ext == extension)
 	break;
     }
 
   if (it == filename_language_table.end ())
     {
       /* New file extension.  */
-      add_filename_language (ext_args, lang);
+      add_filename_language (extension.data (), lang);
     }
   else
     {
@@ -3784,8 +3785,7 @@ test_set_ext_lang_command ()
   SELF_CHECK (lang == language_unknown);
 
   /* Test adding a new extension using the CLI command.  */
-  auto args_holder = make_unique_xstrdup (".hello rust");
-  ext_args = args_holder.get ();
+  ext_args = ".hello rust";
   set_ext_lang_command (NULL, 1, NULL);
 
   lang = deduce_language_from_filename ("cake.hello");
@@ -3793,8 +3793,7 @@ test_set_ext_lang_command ()
 
   /* Test overriding an existing extension using the CLI command.  */
   int size_before = filename_language_table.size ();
-  args_holder.reset (xstrdup (".hello pascal"));
-  ext_args = args_holder.get ();
+  ext_args = ".hello pascal";
   set_ext_lang_command (NULL, 1, NULL);
   int size_after = filename_language_table.size ();
 

gdb/symtab.c

@@ -5146,12 +5146,7 @@ struct info_vars_funcs_options
 {
   bool quiet = false;
   bool exclude_minsyms = false;
-  char *type_regexp = nullptr;
-
-  ~info_vars_funcs_options ()
-  {
-    xfree (type_regexp);
-  }
+  std::string type_regexp;
 };
 
 /* The options used by the 'info variables' and 'info functions'
@@ -5174,8 +5169,7 @@ static const gdb::option::option_def info_vars_funcs_options_defs[] = {
 
   gdb::option::string_option_def<info_vars_funcs_options> {
     "t",
-    [] (info_vars_funcs_options *opt) { return &opt->type_regexp;
-  },
+    [] (info_vars_funcs_options *opt) { return &opt->type_regexp; },
     nullptr, /* show_cmd_cb */
     nullptr /* set_doc */
   }
@@ -5219,8 +5213,10 @@ info_variables_command (const char *args, int from_tty)
   if (args != nullptr && *args == '\0')
     args = nullptr;
 
-  symtab_symbol_info (opts.quiet, opts.exclude_minsyms, args, VARIABLES_DOMAIN,
-		      opts.type_regexp, from_tty);
+  symtab_symbol_info
+    (opts.quiet, opts.exclude_minsyms, args, VARIABLES_DOMAIN,
+     opts.type_regexp.empty () ? nullptr : opts.type_regexp.c_str (),
+     from_tty);
 }
 
 /* Implement the 'info functions' command.  */
@@ -5236,8 +5232,10 @@ info_functions_command (const char *args, int from_tty)
   if (args != nullptr && *args == '\0')
     args = nullptr;
 
-  symtab_symbol_info (opts.quiet, opts.exclude_minsyms, args,
-		      FUNCTIONS_DOMAIN, opts.type_regexp, from_tty);
+  symtab_symbol_info
+    (opts.quiet, opts.exclude_minsyms, args, FUNCTIONS_DOMAIN,
+     opts.type_regexp.empty () ? nullptr : opts.type_regexp.c_str (),
+     from_tty);
 }
 
 /* Holds the -q option for the 'info types' command.  */
@@ -6749,14 +6747,8 @@ info_module_subcommand (bool quiet, const char *module_regexp,
 struct info_modules_var_func_options
 {
   bool quiet = false;
-  char *type_regexp = nullptr;
-  char *module_regexp = nullptr;
-
-  ~info_modules_var_func_options ()
-  {
-    xfree (type_regexp);
-    xfree (module_regexp);
-  }
+  std::string type_regexp;
+  std::string module_regexp;
 };
 
 /* The options used by 'info module variables' and 'info module functions'
@@ -6806,8 +6798,11 @@ info_module_functions_command (const char *args, int from_tty)
   if (args != nullptr && *args == '\0')
     args = nullptr;
 
-  info_module_subcommand (opts.quiet, opts.module_regexp, args,
-			  opts.type_regexp, FUNCTIONS_DOMAIN);
+  info_module_subcommand
+    (opts.quiet,
+     opts.module_regexp.empty () ? nullptr : opts.module_regexp.c_str (), args,
+     opts.type_regexp.empty () ? nullptr : opts.type_regexp.c_str (),
+     FUNCTIONS_DOMAIN);
 }
 
 /* Implements the 'info module variables' command.  */
@@ -6822,8 +6817,11 @@ info_module_variables_command (const char *args, int from_tty)
   if (args != nullptr && *args == '\0')
     args = nullptr;
 
-  info_module_subcommand (opts.quiet, opts.module_regexp, args,
-			  opts.type_regexp, VARIABLES_DOMAIN);
+  info_module_subcommand
+    (opts.quiet,
+     opts.module_regexp.empty () ? nullptr : opts.module_regexp.c_str (), args,
+     opts.type_regexp.empty () ? nullptr : opts.type_regexp.c_str (),
+     VARIABLES_DOMAIN);
 }
 
 /* Command completer for 'info module ...' sub-commands.  */

gdb/target-descriptions.c

@@ -510,7 +510,7 @@ target_desc_info_free (struct target_desc_info *tdesc_info)
 
 /* The string manipulated by the "set tdesc filename ..." command.  */
 
-static char *tdesc_filename_cmd_string;
+static std::string tdesc_filename_cmd_string;
 
 /* Fetch the current target's description, and switch the current
    architecture to one which incorporates that description.  */

gdb/top.c

@@ -84,8 +84,6 @@
 
 extern void initialize_all_files (void);
 
-static bool history_filename_empty (void);
-
 #define PROMPT(X) the_prompts.prompt_stack[the_prompts.top + X].prompt
 #define PREFIX(X) the_prompts.prompt_stack[the_prompts.top + X].prefix
 #define SUFFIX(X) the_prompts.prompt_stack[the_prompts.top + X].suffix
@@ -908,12 +906,16 @@ static bool command_editing_p;
    variable must be set to something sensible.  */
 static bool write_history_p;
 
+/* The name of the file in which GDB history will be written.  If this is
+   set to NULL, of the empty string then history will not be written.  */
+static std::string history_filename;
+
 /* Implement 'show history save'.  */
 static void
 show_write_history_p (struct ui_file *file, int from_tty,
 		      struct cmd_list_element *c, const char *value)
 {
-  if (!write_history_p || !history_filename_empty ())
+  if (!write_history_p || !history_filename.empty ())
     fprintf_filtered (file, _("Saving of the history record on exit is %s.\n"),
 		      value);
   else
@@ -947,24 +949,12 @@ show_history_remove_duplicates (struct ui_file *file, int from_tty,
 		    value);
 }
 
-/* The name of the file in which GDB history will be written.  If this is
-   set to NULL, of the empty string then history will not be written.  */
-static char *history_filename;
-
-/* Return true if the history_filename is either NULL or the empty string,
-   indicating that we should not try to read, nor write out the history.  */
-static bool
-history_filename_empty (void)
-{
-  return (history_filename == nullptr || *history_filename == '\0');
-}
-
 /* Implement 'show history filename'.  */
 static void
 show_history_filename (struct ui_file *file, int from_tty,
 		       struct cmd_list_element *c, const char *value)
 {
-  if (!history_filename_empty ())
+  if (!history_filename.empty ())
     fprintf_filtered (file, _("The filename in which to record "
 			      "the command history is \"%ps\".\n"),
 		      styled_string (file_name_style.style (), value));
@@ -1231,14 +1221,15 @@ gdb_safe_append_history (void)
   int ret, saved_errno;
 
   std::string local_history_filename
-    = string_printf ("%s-gdb%ld~", history_filename, (long) getpid ());
+    = string_printf ("%s-gdb%ld~", history_filename.c_str (), (long) getpid ());
 
-  ret = rename (history_filename, local_history_filename.c_str ());
+  ret = rename (history_filename.c_str (), local_history_filename.c_str ());
   saved_errno = errno;
   if (ret < 0 && saved_errno != ENOENT)
     {
       warning (_("Could not rename %ps to %ps: %s"),
-	       styled_string (file_name_style.style (), history_filename),
+	       styled_string (file_name_style.style (),
+			      history_filename.c_str ()),
 	       styled_string (file_name_style.style (),
 			      local_history_filename.c_str ()),
 	       safe_strerror (saved_errno));
@@ -1266,11 +1257,11 @@ gdb_safe_append_history (void)
 				   history_max_entries);
 	}
 
-      ret = rename (local_history_filename.c_str (), history_filename);
+      ret = rename (local_history_filename.c_str (), history_filename.c_str ());
       saved_errno = errno;
       if (ret < 0 && saved_errno != EEXIST)
 	warning (_("Could not rename %s to %s: %s"),
-		 local_history_filename.c_str (), history_filename,
+		 local_history_filename.c_str (), history_filename.c_str (),
 		 safe_strerror (saved_errno));
     }
 }
@@ -1643,12 +1634,12 @@ tree, and GDB will still find it.)\n\
 
 /* The current top level prompt, settable with "set prompt", and/or
    with the python `gdb.prompt_hook' hook.  */
-static char *top_prompt;
+static std::string top_prompt;
 
 /* Access method for the GDB prompt string.  */
 
-char *
-get_prompt (void)
+const std::string &
+get_prompt ()
 {
   return top_prompt;
 }
@@ -1658,10 +1649,7 @@ get_prompt (void)
 void
 set_prompt (const char *s)
 {
-  char *p = xstrdup (s);
-
-  xfree (top_prompt);
-  top_prompt = p;
+  top_prompt = s;
 }
 
 
@@ -1801,7 +1789,7 @@ quit_force (int *exit_arg, int from_tty)
   /* Save the history information if it is appropriate to do so.  */
   try
     {
-      if (write_history_p && history_filename)
+      if (write_history_p && !history_filename.empty ())
 	{
 	  int save = 0;
 
@@ -2049,27 +2037,8 @@ init_history (void)
 
   set_readline_history_size (history_size_setshow_var);
 
-  tmpenv = getenv ("GDBHISTFILE");
-  if (tmpenv != nullptr)
-    history_filename = xstrdup (tmpenv);
-  else if (history_filename == nullptr)
-    {
-      /* We include the current directory so that if the user changes
-	 directories the file written will be the same as the one
-	 that was read.  */
-#ifdef __MSDOS__
-      /* No leading dots in file names are allowed on MSDOS.  */
-      const char *fname = "_gdb_history";
-#else
-      const char *fname = ".gdb_history";
-#endif
-
-      gdb::unique_xmalloc_ptr<char> temp (gdb_abspath (fname));
-      history_filename = temp.release ();
-    }
-
-  if (!history_filename_empty ())
-    read_history (history_filename);
+  if (!history_filename.empty ())
+    read_history (history_filename.c_str ());
 }
 
 static void
@@ -2119,21 +2088,20 @@ show_exec_done_display_p (struct ui_file *file, int from_tty,
    Extension languages, for example Python's gdb.parameter API, will read
    the value directory from this variable, so we must ensure that this
    always contains the correct value.  */
-static char *staged_gdb_datadir;
+static std::string staged_gdb_datadir;
 
 /* "set" command for the gdb_datadir configuration variable.  */
 
 static void
 set_gdb_datadir (const char *args, int from_tty, struct cmd_list_element *c)
 {
-  set_gdb_data_directory (staged_gdb_datadir);
+  set_gdb_data_directory (staged_gdb_datadir.c_str ());
 
   /* SET_GDB_DATA_DIRECTORY will resolve relative paths in
      STAGED_GDB_DATADIR, so we now copy the value from GDB_DATADIR
      back into STAGED_GDB_DATADIR so the extension languages can read the
      correct value.  */
-  free (staged_gdb_datadir);
-  staged_gdb_datadir = strdup (gdb_datadir.c_str ());
+  staged_gdb_datadir = gdb_datadir;
 
   gdb::observers::gdb_datadir_changed.notify ();
 }
@@ -2158,12 +2126,13 @@ set_history_filename (const char *args,
   /* We include the current directory so that if the user changes
      directories the file written will be the same as the one
      that was read.  */
-  if (!history_filename_empty () && !IS_ABSOLUTE_PATH (history_filename))
+  if (!history_filename.empty ()
+      && !IS_ABSOLUTE_PATH (history_filename.c_str ()))
     {
-      gdb::unique_xmalloc_ptr<char> temp (gdb_abspath (history_filename));
+      gdb::unique_xmalloc_ptr<char> temp
+	(gdb_abspath (history_filename.c_str ()));
 
-      xfree (history_filename);
-      history_filename = temp.release ();
+      history_filename = temp.get ();
     }
 }
 
@@ -2329,7 +2298,7 @@ When set, GDB uses the specified path to search for data files."),
 			   &setlist,
 			    &showlist);
   /* Prime the initial value for data-directory.  */
-  staged_gdb_datadir = strdup (gdb_datadir.c_str ());
+  staged_gdb_datadir = gdb_datadir;
 
   add_setshow_auto_boolean_cmd ("interactive-mode", class_support,
 				&interactive_mode, _("\
@@ -2415,3 +2384,28 @@ gdb_init ()
   /* Create $_gdb_major and $_gdb_minor convenience variables.  */
   init_gdb_version_vars ();
 }
+
+void _initialize_top ();
+void
+_initialize_top ()
+{
+  /* Determine a default value for the history filename.  */
+  const char *tmpenv = getenv ("GDBHISTFILE");
+  if (tmpenv != nullptr)
+    history_filename = tmpenv;
+  else
+    {
+      /* We include the current directory so that if the user changes
+	 directories the file written will be the same as the one
+	 that was read.  */
+#ifdef __MSDOS__
+      /* No leading dots in file names are allowed on MSDOS.  */
+      const char *fname = "_gdb_history";
+#else
+      const char *fname = ".gdb_history";
+#endif
+
+      gdb::unique_xmalloc_ptr<char> temp (gdb_abspath (fname));
+      history_filename = temp.get ();
+    }
+}

gdb/top.h

@@ -261,7 +261,7 @@ 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.  */
-extern char *get_prompt (void);
+extern const std::string &get_prompt ();
 
 /* This function returns a pointer to the string that is used
    by gdb for its command prompt.  */

gdb/tracepoint.c

@@ -130,7 +130,7 @@ static traceframe_info_up current_traceframe_info;
 static struct cmd_list_element *tfindlist;
 
 /* List of expressions to collect by default at each tracepoint hit.  */
-char *default_collect;
+std::string default_collect;
 
 static bool disconnected_tracing;
 
@@ -146,15 +146,15 @@ static int trace_buffer_size = -1;
 
 /* Textual notes applying to the current and/or future trace runs.  */
 
-static char *trace_user = NULL;
+static std::string trace_user;
 
 /* Textual notes applying to the current and/or future trace runs.  */
 
-static char *trace_notes = NULL;
+static std::string trace_notes;
 
 /* Textual notes applying to the stopping of a trace.  */
 
-static char *trace_stop_notes = NULL;
+static std::string trace_stop_notes;
 
 /* support routines */
 
@@ -1688,10 +1688,11 @@ start_tracing (const char *notes)
   target_set_trace_buffer_size (trace_buffer_size);
 
   if (!notes)
-    notes = trace_notes;
-  ret = target_set_trace_notes (trace_user, notes, NULL);
+    notes = trace_notes.c_str ();
 
-  if (!ret && (trace_user || notes))
+  ret = target_set_trace_notes (trace_user.c_str (), notes, NULL);
+
+  if (!ret && (!trace_user.empty () || notes))
     warning (_("Target does not support trace user/notes, info ignored"));
 
   /* Now insert traps and begin collecting data.  */
@@ -1764,7 +1765,8 @@ stop_tracing (const char *note)
     }
 
   if (!note)
-    note = trace_stop_notes;
+    note = trace_stop_notes.c_str ();
+
   ret = target_set_trace_notes (NULL, NULL, note);
 
   if (!ret && note)
@@ -2804,10 +2806,10 @@ all_tracepoint_actions (struct breakpoint *t)
      validation is per-tracepoint (local var "xyz" might be valid for
      one tracepoint and not another, etc), we make up the action on
      the fly, and don't cache it.  */
-  if (*default_collect)
+  if (!default_collect.empty ())
     {
       gdb::unique_xmalloc_ptr<char> default_collect_line
-	(xstrprintf ("collect %s", default_collect));
+	(xstrprintf ("collect %s", default_collect.c_str ()));
 
       validate_actionline (default_collect_line.get (), t);
       actions.reset (new struct command_line (simple_control,
@@ -2896,7 +2898,7 @@ set_trace_user (const char *args, int from_tty,
 {
   int ret;
 
-  ret = target_set_trace_notes (trace_user, NULL, NULL);
+  ret = target_set_trace_notes (trace_user.c_str (), NULL, NULL);
 
   if (!ret)
     warning (_("Target does not support trace notes, user ignored"));
@@ -2908,7 +2910,7 @@ set_trace_notes (const char *args, int from_tty,
 {
   int ret;
 
-  ret = target_set_trace_notes (NULL, trace_notes, NULL);
+  ret = target_set_trace_notes (NULL, trace_notes.c_str (), NULL);
 
   if (!ret)
     warning (_("Target does not support trace notes, note ignored"));
@@ -2920,7 +2922,7 @@ set_trace_stop_notes (const char *args, int from_tty,
 {
   int ret;
 
-  ret = target_set_trace_notes (NULL, NULL, trace_stop_notes);
+  ret = target_set_trace_notes (NULL, NULL, trace_stop_notes.c_str ());
 
   if (!ret)
     warning (_("Target does not support trace notes, stop note ignored"));
@@ -4137,7 +4139,6 @@ Tracepoint actions may include collecting of specified data,\n\
 single-stepping, or enabling/disabling other tracepoints,\n\
 depending on target's capabilities."));
 
-  default_collect = xstrdup ("");
   add_setshow_string_cmd ("default-collect", class_trace,
 			  &default_collect, _("\
 Set the list of expressions to collect by default."), _("\

gdb/tracepoint.h

@@ -159,7 +159,7 @@ struct trace_status
 
 struct trace_status *current_trace_status (void);
 
-extern char *default_collect;
+extern std::string default_collect;
 
 extern int trace_regblock_size;