gdb: generate the prefix name for prefix commands on demand

Previously, the prefixname field of struct cmd_list_element was manually
set for prefix commands.  This seems verbose and error prone as it
required every single call to functions adding prefix commands to
specify the prefix name while the same information can be easily
generated.

Historically, this was not possible as the prefix field was null for
many commands, but this was fixed in commit
3f4d92ebdf7f848b5ccc9e8d8e8514c64fde1183 by Philippe Waroquiers, so
we can rely on the prefix field being set when generating the prefix
name.

This commit also fixes a use after free in this scenario:
* A command gets created via Python (using the gdb.Command class).
  The prefix name member is dynamically allocated.
* An alias to the new command is created. The alias's prefixname is set
  to point to the prefixname for the original command with a direct
  assignment.
* A new command with the same name as the Python command is created.
* The object for the original Python command gets freed and its
  prefixname gets freed as well.
* The alias is updated to point to the new command, but its prefixname
  is not updated so it keeps pointing to the freed one.

gdb/ChangeLog:

	* command.h (add_prefix_cmd): Remove the prefixname argument as
	it can now be generated automatically.  Update all callers.
	(add_basic_prefix_cmd): Ditto.
	(add_show_prefix_cmd): Ditto.
	(add_prefix_cmd_suppress_notification): Ditto.
	(add_abbrev_prefix_cmd): Ditto.
	* cli/cli-decode.c (add_prefix_cmd): Ditto.
	(add_basic_prefix_cmd): Ditto.
	(add_show_prefix_cmd): Ditto.
	(add_prefix_cmd_suppress_notification): Ditto.
	(add_prefix_cmd_suppress_notification): Ditto.
	(add_abbrev_prefix_cmd): Ditto.
	* cli/cli-decode.h (struct cmd_list_element): Replace the
	prefixname member variable with a method which generates the
	prefix name at runtime.  Update all code reading the prefix
	name to use the method, and remove all code setting it.
	* python/py-cmd.c (cmdpy_destroyer): Remove code to free the
	prefixname member as it's now a method.
	(cmdpy_function): Determine if the command is a prefix by
	looking at prefixlist, not prefixname.

69 files changed, 236 insertions, 285 deletions

diff --git a/gdb/ada-lang.c b/gdb/ada-lang.c
index 34b0e92..2a257c2 100644
--- a/gdb/ada-lang.c
+++ b/gdb/ada-lang.c
@@ -13389,11 +13389,11 @@ _initialize_ada_language ()
 
   add_basic_prefix_cmd ("ada", no_class,
 			_("Prefix command for changing Ada-specific settings."),
-			&set_ada_list, "set ada ", 0, &setlist);
+			&set_ada_list, 0, &setlist);
 
   add_show_prefix_cmd ("ada", no_class,
 		       _("Generic command for showing Ada-specific settings."),
-		       &show_ada_list, "show ada ", 0, &showlist);
+		       &show_ada_list, 0, &showlist);
 
   add_setshow_boolean_cmd ("trust-PAD-over-XVS", class_obscure,
 			   &trust_pad_over_xvs, _("\
@@ -13472,12 +13472,12 @@ the regular expression are listed."));
 
   add_basic_prefix_cmd ("ada", class_maintenance,
 			_("Set Ada maintenance-related variables."),
-			&maint_set_ada_cmdlist, "maintenance set ada ",
+			&maint_set_ada_cmdlist,
 			0/*allow-unknown*/, &maintenance_set_cmdlist);
 
   add_show_prefix_cmd ("ada", class_maintenance,
 		       _("Show Ada maintenance-related variables."),
-		       &maint_show_ada_cmdlist, "maintenance show ada ",
+		       &maint_show_ada_cmdlist,
 		       0/*allow-unknown*/, &maintenance_show_cmdlist);
 
   add_setshow_boolean_cmd
diff --git a/gdb/arc-tdep.c b/gdb/arc-tdep.c
index 8a1da1a..ece8025 100644
--- a/gdb/arc-tdep.c
+++ b/gdb/arc-tdep.c
@@ -2495,7 +2495,7 @@ _initialize_arc_tdep ()
   add_show_prefix_cmd ("arc", class_maintenance,
 		       _("ARC-specific maintenance commands for printing GDB "
 			 "internal state."),
-		       &maintenance_print_arc_list, "maintenance print arc ",
+		       &maintenance_print_arc_list,
 		       0, &maintenanceprintlist);
 
   add_cmd ("arc-instruction", class_maintenance,
diff --git a/gdb/arm-tdep.c b/gdb/arm-tdep.c
index c473843..7f56d00 100644
--- a/gdb/arm-tdep.c
+++ b/gdb/arm-tdep.c
@@ -9563,11 +9563,11 @@ _initialize_arm_tdep ()
   /* Add root prefix command for all "set arm"/"show arm" commands.  */
   add_basic_prefix_cmd ("arm", no_class,
 			_("Various ARM-specific commands."),
-			&setarmcmdlist, "set arm ", 0, &setlist);
+			&setarmcmdlist, 0, &setlist);
 
   add_show_prefix_cmd ("arm", no_class,
 		       _("Various ARM-specific commands."),
-		       &showarmcmdlist, "show arm ", 0, &showlist);
+		       &showarmcmdlist, 0, &showlist);
 
 
   arm_disassembler_options = xstrdup ("reg-names-std");
diff --git a/gdb/auto-load.c b/gdb/auto-load.c
index d1ae6de..b9478c4 100644
--- a/gdb/auto-load.c
+++ b/gdb/auto-load.c
@@ -1427,8 +1427,7 @@ auto_load_set_cmdlist_get (void)
 Auto-loading specific settings.\n\
 Configure various auto-load-specific variables such as\n\
 automatic loading of Python scripts."),
-		    &retval, "set auto-load ",
-		    1/*allow-unknown*/, &setlist);
+		    &retval, 1/*allow-unknown*/, &setlist);
 
   return &retval;
 }
@@ -1445,8 +1444,7 @@ auto_load_show_cmdlist_get (void)
 Show auto-loading specific settings.\n\
 Show configuration of various auto-load-specific variables such as\n\
 automatic loading of Python scripts."),
-			 &retval, "show auto-load ",
-			 0/*allow-unknown*/, &showlist);
+			 &retval, 0/*allow-unknown*/, &showlist);
 
   return &retval;
 }
@@ -1488,8 +1486,7 @@ auto_load_info_cmdlist_get (void)
 Print current status of auto-loaded files.\n\
 Print whether various files like Python scripts or .gdbinit files have been\n\
 found and/or loaded."),
-		    &retval, "info auto-load ",
-		    0/*allow-unknown*/, &infolist);
+		    &retval, 0/*allow-unknown*/, &infolist);
 
   return &retval;
 }
diff --git a/gdb/breakpoint.c b/gdb/breakpoint.c
index 38406b4..d479f00 100644
--- a/gdb/breakpoint.c
+++ b/gdb/breakpoint.c
@@ -15731,7 +15731,7 @@ Give breakpoint numbers (separated by spaces) as arguments.\n\
 With no subcommand, breakpoints are enabled until you command otherwise.\n\
 This is used to cancel the effect of the \"disable\" command.\n\
 With a subcommand you can enable temporarily."),
-		  &enablelist, "enable ", 1, &cmdlist);
+		  &enablelist, 1, &cmdlist);
 
   add_com_alias ("en", "enable", class_breakpoint, 1);
 
@@ -15741,7 +15741,7 @@ Usage: enable breakpoints [BREAKPOINTNUM]...\n\
 Give breakpoint numbers (separated by spaces) as arguments.\n\
 This is used to cancel the effect of the \"disable\" command.\n\
 May be abbreviated to simply \"enable\"."),
-		   &enablebreaklist, "enable breakpoints ", 1, &enablelist);
+		   &enablebreaklist, 1, &enablelist);
 
   add_cmd ("once", no_class, enable_once_command, _("\
 Enable some breakpoints for one hit.\n\
@@ -15787,7 +15787,7 @@ Usage: disable [BREAKPOINTNUM]...\n\
 Arguments are breakpoint numbers with spaces in between.\n\
 To disable all breakpoints, give no argument.\n\
 A disabled breakpoint is not forgotten, but has no effect until re-enabled."),
-		  &disablelist, "disable ", 1, &cmdlist);
+		  &disablelist, 1, &cmdlist);
   add_com_alias ("dis", "disable", class_breakpoint, 1);
   add_com_alias ("disa", "disable", class_breakpoint, 1);
 
@@ -15807,7 +15807,7 @@ Arguments are breakpoint numbers with spaces in between.\n\
 To delete all breakpoints, give no argument.\n\
 \n\
 Also a prefix command for deletion of other GDB objects."),
-		  &deletelist, "delete ", 1, &cmdlist);
+		  &deletelist, 1, &cmdlist);
   add_com_alias ("d", "delete", class_breakpoint, 1);
   add_com_alias ("del", "delete", class_breakpoint, 1);
 
@@ -15843,7 +15843,7 @@ BREAK_ARGS_HELP ("break")));
     {
       add_abbrev_prefix_cmd ("stop", class_breakpoint, stop_command, _("\
 Break in function/address or break at a line in the current file."),
-			     &stoplist, "stop ", 1, &cmdlist);
+			     &stoplist, 1, &cmdlist);
       add_cmd ("in", class_breakpoint, stopin_command,
 	       _("Break in function or address."), &stoplist);
       add_cmd ("at", class_breakpoint, stopat_command,
@@ -15906,12 +15906,12 @@ breakpoint set."),
 
   add_basic_prefix_cmd ("catch", class_breakpoint, _("\
 Set catchpoints to catch events."),
-			&catch_cmdlist, "catch ",
+			&catch_cmdlist,
 			0/*allow-unknown*/, &cmdlist);
 
   add_basic_prefix_cmd ("tcatch", class_breakpoint, _("\
 Set temporary catchpoints to catch events."),
-			&tcatch_cmdlist, "tcatch ",
+			&tcatch_cmdlist,
 			0/*allow-unknown*/, &cmdlist);
 
   add_catch_command ("fork", _("Catch calls to fork."),
@@ -16083,7 +16083,7 @@ if TPNUM is omitted, passcount refers to the last tracepoint defined."));
 
   add_basic_prefix_cmd ("save", class_breakpoint,
 			_("Save breakpoint definitions as a script."),
-			&save_cmdlist, "save ",
+			&save_cmdlist,
 			0/*allow-unknown*/, &cmdlist);
 
   c = add_cmd ("breakpoints", class_breakpoint, save_breakpoints_command, _("\
@@ -16107,13 +16107,13 @@ Use the 'source' command in another debug session to restore them."),
 Breakpoint specific settings.\n\
 Configure various breakpoint-specific variables such as\n\
 pending breakpoint behavior."),
-			&breakpoint_set_cmdlist, "set breakpoint ",
+			&breakpoint_set_cmdlist,
 			0/*allow-unknown*/, &setlist);
   add_show_prefix_cmd ("breakpoint", class_maintenance, _("\
 Breakpoint specific settings.\n\
 Configure various breakpoint-specific variables such as\n\
 pending breakpoint behavior."),
-		       &breakpoint_show_cmdlist, "show breakpoint ",
+		       &breakpoint_show_cmdlist,
 		       0/*allow-unknown*/, &showlist);
 
   add_setshow_auto_boolean_cmd ("pending", no_class,
diff --git a/gdb/bsd-kvm.c b/gdb/bsd-kvm.c
index 89da40a..d058aac 100644
--- a/gdb/bsd-kvm.c
+++ b/gdb/bsd-kvm.c
@@ -388,7 +388,7 @@ bsd_kvm_add_target (int (*supply_pcb)(struct regcache *, struct pcb *))
   
   add_prefix_cmd ("kvm", class_obscure, bsd_kvm_cmd, _("\
 Generic command for manipulating the kernel memory interface."),
-		  &bsd_kvm_cmdlist, "kvm ", 0, &cmdlist);
+		  &bsd_kvm_cmdlist, 0, &cmdlist);
 
 #ifndef HAVE_STRUCT_THREAD_TD_PCB
   add_cmd ("proc", class_obscure, bsd_kvm_proc_cmd,
diff --git a/gdb/btrace.c b/gdb/btrace.c
index 17eb56c..5e689c1 100644
--- a/gdb/btrace.c
+++ b/gdb/btrace.c
@@ -3441,29 +3441,26 @@ _initialize_btrace ()
 
   add_basic_prefix_cmd ("btrace", class_maintenance,
 			_("Branch tracing maintenance commands."),
-			&maint_btrace_cmdlist, "maintenance btrace ",
-			0, &maintenancelist);
+			&maint_btrace_cmdlist, 0, &maintenancelist);
 
   add_basic_prefix_cmd ("btrace", class_maintenance, _("\
 Set branch tracing specific variables."),
-			&maint_btrace_set_cmdlist, "maintenance set btrace ",
+			&maint_btrace_set_cmdlist,
 			0, &maintenance_set_cmdlist);
 
   add_basic_prefix_cmd ("pt", class_maintenance, _("\
 Set Intel Processor Trace specific variables."),
 			&maint_btrace_pt_set_cmdlist,
-			"maintenance set btrace pt ",
 			0, &maint_btrace_set_cmdlist);
 
   add_show_prefix_cmd ("btrace", class_maintenance, _("\
 Show branch tracing specific variables."),
-		       &maint_btrace_show_cmdlist, "maintenance show btrace ",
+		       &maint_btrace_show_cmdlist,
 		       0, &maintenance_show_cmdlist);
 
   add_show_prefix_cmd ("pt", class_maintenance, _("\
 Show Intel Processor Trace specific variables."),
 		       &maint_btrace_pt_show_cmdlist,
-		       "maintenance show btrace pt ",
 		       0, &maint_btrace_show_cmdlist);
 
   add_setshow_boolean_cmd ("skip-pad", class_maintenance,
diff --git a/gdb/cli/cli-cmds.c b/gdb/cli/cli-cmds.c
index 62948f5..284b751 100644
--- a/gdb/cli/cli-cmds.c
+++ b/gdb/cli/cli-cmds.c
@@ -2352,10 +2352,10 @@ Show verbosity."), NULL,
 
   add_basic_prefix_cmd ("history", class_support, _("\
 Generic command for setting command history parameters."),
-			&sethistlist, "set history ", 0, &setlist);
+			&sethistlist, 0, &setlist);
   add_show_prefix_cmd ("history", class_support, _("\
 Generic command for showing command history parameters."),
-		       &showhistlist, "show history ", 0, &showlist);
+		       &showhistlist, 0, &showlist);
 
   add_setshow_boolean_cmd ("expansion", no_class, &history_expansion_p, _("\
 Set history expansion on command input."), _("\
@@ -2367,7 +2367,7 @@ Without an argument, history expansion is enabled."),
 
   add_prefix_cmd ("info", class_info, info_command, _("\
 Generic command for showing things about the program being debugged."),
-		  &infolist, "info ", 0, &cmdlist);
+		  &infolist, 0, &cmdlist);
   add_com_alias ("i", "info", class_info, 1);
   add_com_alias ("inf", "info", class_info, 1);
 
@@ -2376,7 +2376,7 @@ Generic command for showing things about the program being debugged."),
 
   c = add_show_prefix_cmd ("show", class_info, _("\
 Generic command for showing things about the debugger."),
-			   &showlist, "show ", 0, &cmdlist);
+			   &showlist, 0, &cmdlist);
   /* Another way to get at the same thing.  */
   add_alias_cmd ("set", c, class_info, 0, &infolist);
 
@@ -2449,11 +2449,11 @@ the previous command number shown."),
 
   add_basic_prefix_cmd ("debug", no_class,
 			_("Generic command for setting gdb debugging flags."),
-			&setdebuglist, "set debug ", 0, &setlist);
+			&setdebuglist, 0, &setlist);
 
   add_show_prefix_cmd ("debug", no_class,
 		       _("Generic command for showing gdb debugging flags."),
-		       &showdebuglist, "show debug ", 0, &showlist);
+		       &showdebuglist, 0, &showlist);
 
   c = add_com ("shell", class_support, shell_command, _("\
 Execute the rest of the line as a shell command.\n\
diff --git a/gdb/cli/cli-decode.c b/gdb/cli/cli-decode.c
index f48a9ad..32edb52 100644
--- a/gdb/cli/cli-decode.c
+++ b/gdb/cli/cli-decode.c
@@ -318,7 +318,6 @@ add_alias_cmd (const char *name, cmd_list_element *old,
   c->func = old->func;
   c->function = old->function;
   c->prefixlist = old->prefixlist;
-  c->prefixname = old->prefixname;
   c->allow_unknown = old->allow_unknown;
   c->abbrev_flag = abbrev_flag;
   c->cmd_pointer = old;
@@ -383,13 +382,11 @@ struct cmd_list_element *
 add_prefix_cmd (const char *name, enum command_class theclass,
 		cmd_const_cfunc_ftype *fun,
 		const char *doc, struct cmd_list_element **prefixlist,
-		const char *prefixname, int allow_unknown,
-		struct cmd_list_element **list)
+		int allow_unknown, struct cmd_list_element **list)
 {
   struct cmd_list_element *c = add_cmd (name, theclass, fun, doc, list);
 
   c->prefixlist = prefixlist;
-  c->prefixname = prefixname;
   c->allow_unknown = allow_unknown;
 
   /* Now that prefix command C is defined, we need to set the prefix field
@@ -409,7 +406,8 @@ do_prefix_cmd (const char *args, int from_tty, struct cmd_list_element *c)
   while (c->cmd_pointer != nullptr)
     c = c->cmd_pointer;
 
-  help_list (*c->prefixlist, c->prefixname, all_commands, gdb_stdout);
+  help_list (*c->prefixlist, c->prefixname ().c_str (),
+	     all_commands, gdb_stdout);
 }
 
 /* See command.h.  */
@@ -417,11 +415,10 @@ do_prefix_cmd (const char *args, int from_tty, struct cmd_list_element *c)
 struct cmd_list_element *
 add_basic_prefix_cmd (const char *name, enum command_class theclass,
 		      const char *doc, struct cmd_list_element **prefixlist,
-		      const char *prefixname, int allow_unknown,
-		      struct cmd_list_element **list)
+		      int allow_unknown, struct cmd_list_element **list)
 {
   struct cmd_list_element *cmd = add_prefix_cmd (name, theclass, nullptr,
-						 doc, prefixlist, prefixname,
+						 doc, prefixlist,
 						 allow_unknown, list);
   set_cmd_sfunc (cmd, do_prefix_cmd);
   return cmd;
@@ -441,11 +438,10 @@ do_show_prefix_cmd (const char *args, int from_tty, struct cmd_list_element *c)
 struct cmd_list_element *
 add_show_prefix_cmd (const char *name, enum command_class theclass,
 		     const char *doc, struct cmd_list_element **prefixlist,
-		     const char *prefixname, int allow_unknown,
-		     struct cmd_list_element **list)
+		     int allow_unknown, struct cmd_list_element **list)
 {
   struct cmd_list_element *cmd = add_prefix_cmd (name, theclass, nullptr,
-						 doc, prefixlist, prefixname,
+						 doc, prefixlist,
 						 allow_unknown, list);
   set_cmd_sfunc (cmd, do_show_prefix_cmd);
   return cmd;
@@ -459,13 +455,12 @@ add_prefix_cmd_suppress_notification
 	       (const char *name, enum command_class theclass,
 		cmd_const_cfunc_ftype *fun,
 		const char *doc, struct cmd_list_element **prefixlist,
-		const char *prefixname, int allow_unknown,
-		struct cmd_list_element **list,
+		int allow_unknown, struct cmd_list_element **list,
 		int *suppress_notification)
 {
   struct cmd_list_element *element
     = add_prefix_cmd (name, theclass, fun, doc, prefixlist,
-		      prefixname, allow_unknown, list);
+		      allow_unknown, list);
   element->suppress_notification = suppress_notification;
   return element;
 }
@@ -476,13 +471,11 @@ struct cmd_list_element *
 add_abbrev_prefix_cmd (const char *name, enum command_class theclass,
 		       cmd_const_cfunc_ftype *fun, const char *doc,
 		       struct cmd_list_element **prefixlist,
-		       const char *prefixname,
 		       int allow_unknown, struct cmd_list_element **list)
 {
   struct cmd_list_element *c = add_cmd (name, theclass, fun, doc, list);
 
   c->prefixlist = prefixlist;
-  c->prefixname = prefixname;
   c->allow_unknown = allow_unknown;
   c->abbrev_flag = 1;
   return c;
@@ -1034,10 +1027,11 @@ add_com_suppress_notification (const char *name, enum command_class theclass,
 static void
 fput_command_name_styled (struct cmd_list_element *c, struct ui_file *stream)
 {
-  const char *prefixname
-    = c->prefix == nullptr ? "" : c->prefix->prefixname;
+  std::string prefixname
+    = c->prefix == nullptr ? "" : c->prefix->prefixname ();
 
-  fprintf_styled (stream, title_style.style (), "%s%s", prefixname, c->name);
+  fprintf_styled (stream, title_style.style (), "%s%s",
+		  prefixname.c_str (), c->name);
 }
 
 /* Print the definition of alias C using title style for alias
@@ -1192,7 +1186,8 @@ apropos_cmd (struct ui_file *stream,
 	{
 	  /* Recursively call ourselves on the subcommand list,
 	     passing the right prefix in.  */
-	  apropos_cmd (stream, *c->prefixlist, verbose, regex, c->prefixname);
+	  apropos_cmd (stream, *c->prefixlist, verbose, regex,
+		       c->prefixname ().c_str ());
 	}
     }
 }
@@ -1258,7 +1253,8 @@ help_cmd (const char *command, struct ui_file *stream)
 
   /* If this is a prefix command, print it's subcommands.  */
   if (c->prefixlist)
-    help_list (*c->prefixlist, c->prefixname, all_commands, stream);
+    help_list (*c->prefixlist, c->prefixname ().c_str (),
+	       all_commands, stream);
 
   /* If this is a class name, print all of the commands in the class.  */
   if (c->func == NULL)
@@ -1812,7 +1808,8 @@ lookup_cmd (const char **line, struct cmd_list_element *list,
 	 values.  */
       int local_allow_unknown = (last_list ? last_list->allow_unknown :
 				 allow_unknown);
-      const char *local_cmdtype = last_list ? last_list->prefixname : cmdtype;
+      std::string local_cmdtype
+	= last_list ? last_list->prefixname () : cmdtype;
       struct cmd_list_element *local_list =
 	(last_list ? *(last_list->prefixlist) : list);
 
@@ -1852,8 +1849,8 @@ lookup_cmd (const char **line, struct cmd_list_element *list,
 		    break;
 		  }
 	      }
-	  error (_("Ambiguous %scommand \"%s\": %s."), local_cmdtype,
-		 *line, ambbuf);
+	  error (_("Ambiguous %scommand \"%s\": %s."),
+		 local_cmdtype.c_str (), *line, ambbuf);
 	}
     }
   else
@@ -1867,7 +1864,7 @@ lookup_cmd (const char **line, struct cmd_list_element *list,
 	(*line)++;
 
       if (c->prefixlist && **line && !c->allow_unknown)
-	undef_cmd_error (c->prefixname, *line);
+	undef_cmd_error (c->prefixname ().c_str (), *line);
 
       /* Seems to be what he wants.  Return it.  */
       return c;
@@ -1940,7 +1937,7 @@ deprecated_cmd_warning (const char *text, struct cmd_list_element *list)
   /* Join command prefix (if any) and the command name.  */
   std::string tmp_cmd_str;
   if (cmd->prefix != nullptr)
-    tmp_cmd_str += std::string (cmd->prefix->prefixname);
+    tmp_cmd_str += cmd->prefix->prefixname ();
   tmp_cmd_str += std::string (cmd->name);
 
   /* Display the appropriate first line, this warns that the thing the user
@@ -1950,7 +1947,7 @@ deprecated_cmd_warning (const char *text, struct cmd_list_element *list)
       /* Join the alias prefix (if any) and the alias name.  */
       std::string tmp_alias_str;
       if (alias->prefix != nullptr)
-	tmp_alias_str += std::string (alias->prefix->prefixname);
+	tmp_alias_str += alias->prefix->prefixname ();
       tmp_alias_str += std::string (alias->name);
 
       if (cmd->cmd_deprecated)
diff --git a/gdb/cli/cli-decode.h b/gdb/cli/cli-decode.h
index d6f52a2..214428e 100644
--- a/gdb/cli/cli-decode.h
+++ b/gdb/cli/cli-decode.h
@@ -71,6 +71,25 @@ struct cmd_list_element
 
   DISABLE_COPY_AND_ASSIGN (cmd_list_element);
 
+  /* For prefix commands, return a string containing prefix commands to
+     get here: this one plus any others needed to get to it.  Ends in a
+     space.  It is used before the word "command" in describing the
+     commands reached through this prefix.
+
+     For non-prefix commands, an empty string is returned.  */
+  std::string prefixname ()
+  {
+    if (prefixlist == nullptr)
+      /* Not a prefix command.  */
+      return "";
+
+    std::string prefixname;
+    if (prefix != nullptr)
+      prefixname = prefix->prefixname ();
+    prefixname += name;
+    prefixname += " ";
+    return prefixname;
+  }
 
   /* Points to next command in this list.  */
   struct cmd_list_element *next = nullptr;
@@ -186,13 +205,6 @@ struct cmd_list_element
      of the variable containing the list of subcommands.  */
   struct cmd_list_element **prefixlist = nullptr;
 
-  /* For prefix commands only:
-     String containing prefix commands to get here: this one
-     plus any others needed to get to it.  Should end in a space.
-     It is used before the word "command" in describing the
-     commands reached through this prefix.  */
-  const char *prefixname = nullptr;
-
   /* The prefix command of this command.  */
   struct cmd_list_element *prefix = nullptr;
 
diff --git a/gdb/cli/cli-dump.c b/gdb/cli/cli-dump.c
index 1df2662..95ce85e 100644
--- a/gdb/cli/cli-dump.c
+++ b/gdb/cli/cli-dump.c
@@ -572,12 +572,12 @@ _initialize_cli_dump ()
 
   add_basic_prefix_cmd ("dump", class_vars,
 			_("Dump target code/data to a local file."),
-			&dump_cmdlist, "dump ",
+			&dump_cmdlist,
 			0/*allow-unknown*/,
 			&cmdlist);
   add_basic_prefix_cmd ("append", class_vars,
 			_("Append target code/data to a local file."),
-			&append_cmdlist, "append ",
+			&append_cmdlist,
 			0/*allow-unknown*/,
 			&cmdlist);
 
@@ -593,37 +593,37 @@ the specified FILE in raw target ordered bytes.");
 
   add_basic_prefix_cmd ("srec", all_commands,
 			_("Write target code/data to an srec file."),
-			&srec_cmdlist, "dump srec ", 
+			&srec_cmdlist,
 			0 /*allow-unknown*/, 
 			&dump_cmdlist);
 
   add_basic_prefix_cmd ("ihex", all_commands,
 			_("Write target code/data to an intel hex file."),
-			&ihex_cmdlist, "dump ihex ", 
+			&ihex_cmdlist,
 			0 /*allow-unknown*/, 
 			&dump_cmdlist);
 
   add_basic_prefix_cmd ("verilog", all_commands,
 			_("Write target code/data to a verilog hex file."),
-			&verilog_cmdlist, "dump verilog ",
+			&verilog_cmdlist,
 			0 /*allow-unknown*/,
 			&dump_cmdlist);
 
   add_basic_prefix_cmd ("tekhex", all_commands,
 			_("Write target code/data to a tekhex file."),
-			&tekhex_cmdlist, "dump tekhex ", 
+			&tekhex_cmdlist,
 			0 /*allow-unknown*/, 
 			&dump_cmdlist);
 
   add_basic_prefix_cmd ("binary", all_commands,
 			_("Write target code/data to a raw binary file."),
-			&binary_dump_cmdlist, "dump binary ", 
+			&binary_dump_cmdlist,
 			0 /*allow-unknown*/, 
 			&dump_cmdlist);
 
   add_basic_prefix_cmd ("binary", all_commands,
 			_("Append target code/data to a raw binary file."),
-			&binary_append_cmdlist, "append binary ", 
+			&binary_append_cmdlist,
 			0 /*allow-unknown*/, 
 			&append_cmdlist);
 
diff --git a/gdb/cli/cli-logging.c b/gdb/cli/cli-logging.c
index 9cde7b9..dfedd75 100644
--- a/gdb/cli/cli-logging.c
+++ b/gdb/cli/cli-logging.c
@@ -173,10 +173,10 @@ _initialize_cli_logging ()
 
   add_basic_prefix_cmd ("logging", class_support,
 			_("Set logging options."), &set_logging_cmdlist,
-			"set logging ", 0, &setlist);
+			0, &setlist);
   add_show_prefix_cmd ("logging", class_support,
 		       _("Show logging options."), &show_logging_cmdlist,
-		       "show logging ", 0, &showlist);
+		       0, &showlist);
   add_setshow_boolean_cmd ("overwrite", class_support, &logging_overwrite, _("\
 Set whether logging overwrites or appends to the log file."), _("\
 Show whether logging overwrites or appends to the log file."), _("\
diff --git a/gdb/cli/cli-script.c b/gdb/cli/cli-script.c
index 0544f3e..eb8853a 100644
--- a/gdb/cli/cli-script.c
+++ b/gdb/cli/cli-script.c
@@ -1472,7 +1472,6 @@ do_define_command (const char *comname, int from_tty,
   {
     struct cmd_list_element **c_prefixlist
       = c == nullptr ? nullptr : c->prefixlist;
-    const char *c_prefixname = c == nullptr ? nullptr : c->prefixname;
 
     newc = add_cmd (comname, class_user, user_defined_command,
 		    (c != nullptr && c->theclass == class_user)
@@ -1484,7 +1483,6 @@ do_define_command (const char *comname, int from_tty,
     if (c_prefixlist != nullptr)
       {
 	newc->prefixlist = c_prefixlist;
-	newc->prefixname = c_prefixname;
 	/* allow_unknown: see explanation in equivalent logic in
 	   define_prefix_command ().  */
 	newc->allow_unknown = newc->user_commands.get () != nullptr;
@@ -1615,7 +1613,6 @@ define_prefix_command (const char *comname, int from_tty)
      command.  */
   c->prefixlist = new struct cmd_list_element*;
   *(c->prefixlist) = nullptr;
-  c->prefixname = xstrprintf ("%s ", comfull);
   /* If the prefix command C is not a command, then it must be followed
      by known subcommands.  Otherwise, if C is also a normal command,
      it can be followed by C args that must not cause a 'subcommand'
@@ -1681,11 +1678,11 @@ show_user_1 (struct cmd_list_element *c, const char *prefix, const char *name,
 
   if (c->prefixlist != NULL)
     {
-      const char *prefixname = c->prefixname;
+      const std::string prefixname = c->prefixname ();
 
       for (c = *c->prefixlist; c != NULL; c = c->next)
 	if (c->theclass == class_user || c->prefixlist != NULL)
-	  show_user_1 (c, prefixname, c->name, gdb_stdout);
+	  show_user_1 (c, prefixname.c_str (), c->name, gdb_stdout);
     }
 
 }
diff --git a/gdb/cli/cli-setshow.c b/gdb/cli/cli-setshow.c
index 1a8c6e2..1b14df7 100644
--- a/gdb/cli/cli-setshow.c
+++ b/gdb/cli/cli-setshow.c
@@ -747,7 +747,8 @@ cmd_show_list (struct cmd_list_element *list, int from_tty)
       if (list->prefixlist && list->cmd_pointer == nullptr)
 	{
 	  ui_out_emit_tuple optionlist_emitter (uiout, "optionlist");
-	  const char *new_prefix = strstr (list->prefixname, "show ") + 5;
+	  std::string prefixname = list->prefixname ();
+	  const char *new_prefix = strstr (prefixname.c_str (), "show ") + 5;
 
 	  if (uiout->is_mi_like_p ())
 	    uiout->field_string ("prefix", new_prefix);
@@ -757,13 +758,14 @@ cmd_show_list (struct cmd_list_element *list, int from_tty)
 	{
 	  ui_out_emit_tuple option_emitter (uiout, "option");
 
-	  {
-	    /* If we find a prefix, output it (with "show " skipped).  */
-	    const char *prefixname
-	      = (list->prefix == nullptr ? ""
-		 : strstr (list->prefix->prefixname, "show ") + 5);
-	    uiout->text (prefixname);
-	  }
+	  if (list->prefix != nullptr)
+	    {
+	      /* If we find a prefix, output it (with "show " skipped).  */
+	      std::string prefixname = list->prefix->prefixname ();
+	      prefixname = (list->prefix->prefixlist == nullptr ? ""
+			    : strstr (prefixname.c_str (), "show ") + 5);
+	      uiout->text (prefixname.c_str ());
+	    }
 	  uiout->field_string ("name", list->name);
 	  uiout->text (":  ");
 	  if (list->type == show_cmd)
diff --git a/gdb/cli/cli-style.c b/gdb/cli/cli-style.c
index 8b4b6b2..25a1d88 100644
--- a/gdb/cli/cli-style.c
+++ b/gdb/cli/cli-style.c
@@ -225,13 +225,10 @@ cli_style_option::add_setshow_commands (enum command_class theclass,
 					struct cmd_list_element **show_list,
 					bool skip_intensity)
 {
-  m_set_prefix = std::string ("set style ") + m_name + " ";
-  m_show_prefix = std::string ("show style ") + m_name + " ";
-
   add_basic_prefix_cmd (m_name, no_class, prefix_doc, &m_set_list,
-			m_set_prefix.c_str (), 0, set_list);
+			0, set_list);
   add_show_prefix_cmd (m_name, no_class, prefix_doc, &m_show_list,
-		       m_show_prefix.c_str (), 0, show_list);
+		       0, show_list);
 
   add_setshow_enum_cmd ("foreground", theclass, cli_colors,
 			&m_foreground,
@@ -297,11 +294,11 @@ _initialize_cli_style ()
   add_basic_prefix_cmd ("style", no_class, _("\
 Style-specific settings.\n\
 Configure various style-related variables, such as colors"),
-		  &style_set_list, "set style ", 0, &setlist);
+		  &style_set_list, 0, &setlist);
   add_show_prefix_cmd ("style", no_class, _("\
 Style-specific settings.\n\
 Configure various style-related variables, such as colors"),
-		  &style_show_list, "show style ", 0, &showlist);
+		  &style_show_list, 0, &showlist);
 
   add_setshow_boolean_cmd ("enabled", no_class, &cli_styling, _("\
 Set whether CLI styling is enabled."), _("\
diff --git a/gdb/cli/cli-style.h b/gdb/cli/cli-style.h
index 187e1d0..78bc2cd 100644
--- a/gdb/cli/cli-style.h
+++ b/gdb/cli/cli-style.h
@@ -72,9 +72,6 @@ private:
   /* The intensity.  */
   const char *m_intensity;
 
-  /* Storage for prefixes needed when registering the commands.  */
-  std::string m_show_prefix;
-  std::string m_set_prefix;
   /* Storage for command lists needed when registering
      subcommands.  */
   struct cmd_list_element *m_set_list = nullptr;
diff --git a/gdb/command.h b/gdb/command.h
index 827a196..33feb19 100644
--- a/gdb/command.h
+++ b/gdb/command.h
@@ -188,7 +188,7 @@ extern struct cmd_list_element *add_prefix_cmd (const char *, enum command_class
 						cmd_const_cfunc_ftype *fun,
 						const char *,
 						struct cmd_list_element **,
-						const char *, int,
+						int,
 						struct cmd_list_element **);
 
 /* Like add_prefix_cmd, but sets the callback to a function that
@@ -196,20 +196,20 @@ extern struct cmd_list_element *add_prefix_cmd (const char *, enum command_class
 
 extern struct cmd_list_element *add_basic_prefix_cmd
   (const char *, enum command_class, const char *, struct cmd_list_element **,
-   const char *, int, struct cmd_list_element **);
+   int, struct cmd_list_element **);
 
 /* Like add_prefix_cmd, but useful for "show" prefixes.  This sets the
    callback to a function that simply calls cmd_show_list.  */
 
 extern struct cmd_list_element *add_show_prefix_cmd
   (const char *, enum command_class, const char *, struct cmd_list_element **,
-   const char *, int, struct cmd_list_element **);
+   int, struct cmd_list_element **);
 
 extern struct cmd_list_element *add_prefix_cmd_suppress_notification
 			(const char *name, enum command_class theclass,
 			 cmd_const_cfunc_ftype *fun,
 			 const char *doc, struct cmd_list_element **prefixlist,
-			 const char *prefixname, int allow_unknown,
+			 int allow_unknown,
 			 struct cmd_list_element **list,
 			 int *suppress_notification);
 
@@ -218,7 +218,7 @@ extern struct cmd_list_element *add_abbrev_prefix_cmd (const char *,
 						       cmd_const_cfunc_ftype *fun,
 						       const char *,
 						       struct cmd_list_element
-						       **, const char *, int,
+						       **, int,
 						       struct cmd_list_element
 						       **);
 
diff --git a/gdb/compile/compile.c b/gdb/compile/compile.c
index 5c5d517..c7f7d38 100644
--- a/gdb/compile/compile.c
+++ b/gdb/compile/compile.c
@@ -930,7 +930,7 @@ _initialize_compile ()
   compile_cmd_element = add_prefix_cmd ("compile", class_obscure,
 					compile_command, _("\
 Command to compile source code and inject it into the inferior."),
-		  &compile_command_list, "compile ", 1, &cmdlist);
+		  &compile_command_list, 1, &cmdlist);
   add_com_alias ("expression", "compile", class_obscure, 0);
 
   const auto compile_opts = make_compile_options_def_group (nullptr);
diff --git a/gdb/cp-support.c b/gdb/cp-support.c
index eba477d..e87c9d4 100644
--- a/gdb/cp-support.c
+++ b/gdb/cp-support.c
@@ -2212,7 +2212,6 @@ _initialize_cp_support ()
   add_basic_prefix_cmd ("cplus", class_maintenance,
 			_("C++ maintenance commands."),
 			&maint_cplus_cmd_list,
-			"maintenance cplus ",
 			0, &maintenancelist);
   add_alias_cmd ("cp", "cplus",
 		 class_maintenance, 1,
diff --git a/gdb/dcache.c b/gdb/dcache.c
index 201505b..50b3854 100644
--- a/gdb/dcache.c
+++ b/gdb/dcache.c
@@ -696,11 +696,10 @@ the contents of the given line."));
 
   add_basic_prefix_cmd ("dcache", class_obscure, _("\
 Use this command to set number of lines in dcache and line-size."),
-			&dcache_set_list, "set dcache ", /*allow_unknown*/0,
-			&setlist);
+			&dcache_set_list, /*allow_unknown*/0, &setlist);
   add_show_prefix_cmd ("dcache", class_obscure, _("\
 Show dcachesettings."),
-		       &dcache_show_list, "show dcache ", /*allow_unknown*/0,
+		       &dcache_show_list, /*allow_unknown*/0,
 		       &showlist);
 
   add_setshow_zuinteger_cmd ("line-size", class_obscure,
diff --git a/gdb/dwarf2/index-cache.c b/gdb/dwarf2/index-cache.c
index ed8fd8e..c3decf1 100644
--- a/gdb/dwarf2/index-cache.c
+++ b/gdb/dwarf2/index-cache.c
@@ -335,12 +335,12 @@ _initialize_index_cache ()
   add_basic_prefix_cmd ("index-cache", class_files,
 			_("Set index-cache options."),
 			&set_index_cache_prefix_list,
-			"set index-cache ", false, &setlist);
+			false, &setlist);
 
   /* show index-cache */
   add_prefix_cmd ("index-cache", class_files, show_index_cache_command,
 		  _("Show index-cache options."), &show_index_cache_prefix_list,
-		  "show index-cache ", false, &showlist);
+		  false, &showlist);
 
   /* set index-cache on */
   add_cmd ("on", class_files, set_index_cache_on_command,
diff --git a/gdb/dwarf2/read.c b/gdb/dwarf2/read.c
index b2f48f1..280f56c 100644
--- a/gdb/dwarf2/read.c
+++ b/gdb/dwarf2/read.c
@@ -25079,13 +25079,13 @@ _initialize_dwarf2_read ()
   add_basic_prefix_cmd ("dwarf", class_maintenance, _("\
 Set DWARF specific variables.\n\
 Configure DWARF variables such as the cache size."),
-			&set_dwarf_cmdlist, "maintenance set dwarf ",
+			&set_dwarf_cmdlist,
 			0/*allow-unknown*/, &maintenance_set_cmdlist);
 
   add_show_prefix_cmd ("dwarf", class_maintenance, _("\
 Show DWARF specific variables.\n\
 Show DWARF variables such as the cache size."),
-		       &show_dwarf_cmdlist, "maintenance show dwarf ",
+		       &show_dwarf_cmdlist,
 		       0/*allow-unknown*/, &maintenance_show_cmdlist);
 
   add_setshow_zinteger_cmd ("max-cache-age", class_obscure,
diff --git a/gdb/f-lang.c b/gdb/f-lang.c
index 7e921b9..5731c40 100644
--- a/gdb/f-lang.c
+++ b/gdb/f-lang.c
@@ -1685,11 +1685,11 @@ _initialize_f_language ()
 
   add_basic_prefix_cmd ("fortran", no_class,
 			_("Prefix command for changing Fortran-specific settings."),
-			&set_fortran_list, "set fortran ", 0, &setlist);
+			&set_fortran_list, 0, &setlist);
 
   add_show_prefix_cmd ("fortran", no_class,
 		       _("Generic command for showing Fortran-specific settings."),
-		       &show_fortran_list, "show fortran ", 0, &showlist);
+		       &show_fortran_list, 0, &showlist);
 
   add_setshow_boolean_cmd ("repack-array-slices", class_vars,
 			   &repack_array_slices, _("\
diff --git a/gdb/frame.c b/gdb/frame.c
index cd10f3f..d2e14c8 100644
--- a/gdb/frame.c
+++ b/gdb/frame.c
@@ -3171,12 +3171,12 @@ _initialize_frame ()
   add_basic_prefix_cmd ("backtrace", class_maintenance, _("\
 Set backtrace specific variables.\n\
 Configure backtrace variables such as the backtrace limit"),
-			&set_backtrace_cmdlist, "set backtrace ",
+			&set_backtrace_cmdlist,
 			0/*allow-unknown*/, &setlist);
   add_show_prefix_cmd ("backtrace", class_maintenance, _("\
 Show backtrace specific variables.\n\
 Show backtrace variables such as the backtrace limit."),
-		       &show_backtrace_cmdlist, "show backtrace ",
+		       &show_backtrace_cmdlist,
 		       0/*allow-unknown*/, &showlist);
 
   add_setshow_uinteger_cmd ("limit", class_obscure,
diff --git a/gdb/gnu-nat.c b/gdb/gnu-nat.c
index 816f901..aadd3e8 100644
--- a/gdb/gnu-nat.c
+++ b/gdb/gnu-nat.c
@@ -3238,10 +3238,10 @@ Show whether exceptions in the inferior process will be trapped."),
 
   add_prefix_cmd ("task", no_class, set_task_cmd,
 		  _("Command prefix for setting task attributes."),
-		  &set_task_cmd_list, "set task ", 0, &setlist);
+		  &set_task_cmd_list, 0, &setlist);
   add_prefix_cmd ("task", no_class, show_task_cmd,
 		  _("Command prefix for showing task attributes."),
-		  &show_task_cmd_list, "show task ", 0, &showlist);
+		  &show_task_cmd_list, 0, &showlist);
 
   add_cmd ("pause", class_run, set_task_pause_cmd, _("\
 Set whether the task is suspended while gdb has control.\n\
@@ -3410,17 +3410,17 @@ add_thread_commands (void)
 {
   add_prefix_cmd ("thread", no_class, set_thread_cmd,
 		  _("Command prefix for setting thread properties."),
-		  &set_thread_cmd_list, "set thread ", 0, &setlist);
+		  &set_thread_cmd_list, 0, &setlist);
   add_prefix_cmd ("default", no_class, show_thread_cmd,
 		  _("Command prefix for setting default thread properties."),
-		  &set_thread_default_cmd_list, "set thread default ", 0,
+		  &set_thread_default_cmd_list, 0,
 		  &set_thread_cmd_list);
   add_prefix_cmd ("thread", no_class, set_thread_default_cmd,
 		  _("Command prefix for showing thread properties."),
-		  &show_thread_cmd_list, "show thread ", 0, &showlist);
+		  &show_thread_cmd_list, 0, &showlist);
   add_prefix_cmd ("default", no_class, show_thread_default_cmd,
 		  _("Command prefix for showing default thread properties."),
-		  &show_thread_default_cmd_list, "show thread default ", 0,
+		  &show_thread_default_cmd_list, 0,
 		  &show_thread_cmd_list);
 
   add_cmd ("pause", class_run, set_thread_pause_cmd, _("\
diff --git a/gdb/go32-nat.c b/gdb/go32-nat.c
index 9899545..5aae340 100644
--- a/gdb/go32-nat.c
+++ b/gdb/go32-nat.c
@@ -2099,7 +2099,7 @@ _initialize_go32_nat ()
 
   add_basic_prefix_cmd ("dos", class_info, _("\
 Print information specific to DJGPP (aka MS-DOS) debugging."),
-			&info_dos_cmdlist, "info dos ", 0, &infolist);
+			&info_dos_cmdlist, 0, &infolist);
 
   add_cmd ("sysinfo", class_info, go32_sysinfo, _("\
 Display information about the target system, including CPU, OS, DPMI, etc."),
diff --git a/gdb/guile/guile.c b/gdb/guile/guile.c
index 71d61f3..0166355 100644
--- a/gdb/guile/guile.c
+++ b/gdb/guile/guile.c
@@ -782,20 +782,17 @@ This command is only a placeholder.")
 
   add_basic_prefix_cmd ("guile", class_obscure,
 			_("Prefix command for Guile preference settings."),
-			&set_guile_list, "set guile ", 0,
-			&setlist);
+			&set_guile_list, 0, &setlist);
   add_alias_cmd ("gu", "guile", class_obscure, 1, &setlist);
 
   add_show_prefix_cmd ("guile", class_obscure,
 		       _("Prefix command for Guile preference settings."),
-		       &show_guile_list, "show guile ", 0,
-		       &showlist);
+		       &show_guile_list, 0, &showlist);
   add_alias_cmd ("gu", "guile", class_obscure, 1, &showlist);
 
   add_basic_prefix_cmd ("guile", class_obscure,
 			_("Prefix command for Guile info displays."),
-			&info_guile_list, "info guile ", 0,
-			&infolist);
+			&info_guile_list, 0, &infolist);
   add_info_alias ("gu", "guile", 1);
 
   /* The name "print-stack" is carried over from Python.
diff --git a/gdb/guile/scm-cmd.c b/gdb/guile/scm-cmd.c
index 1708d66..1f35d88 100644
--- a/gdb/guile/scm-cmd.c
+++ b/gdb/guile/scm-cmd.c
@@ -766,7 +766,7 @@ gdbscm_register_command_x (SCM self)
 
 	  cmd = add_prefix_cmd (c_smob->cmd_name, c_smob->cmd_class,
 				NULL, c_smob->doc, &c_smob->sub_list,
-				c_smob->name, allow_unknown, cmd_list);
+				allow_unknown, cmd_list);
 	}
       else
 	{
diff --git a/gdb/i386-tdep.c b/gdb/i386-tdep.c
index 50fd276..5e6769a 100644
--- a/gdb/i386-tdep.c
+++ b/gdb/i386-tdep.c
@@ -9031,14 +9031,14 @@ is \"default\"."),
 
   add_basic_prefix_cmd ("mpx", class_support, _("\
 Set Intel Memory Protection Extensions specific variables."),
-			&mpx_set_cmdlist, "set mpx ",
+			&mpx_set_cmdlist,
 			0 /* allow-unknown */, &setlist);
 
   /* Add "mpx" prefix for the show commands.  */
 
   add_show_prefix_cmd ("mpx", class_support, _("\
 Show Intel Memory Protection Extensions specific variables."),
-		       &mpx_show_cmdlist, "show mpx ",
+		       &mpx_show_cmdlist,
 		       0 /* allow-unknown */, &showlist);
 
   /* Add "bound" command for the show mpx commands list.  */
diff --git a/gdb/infcmd.c b/gdb/infcmd.c
index f0b044d..a22d815 100644
--- a/gdb/infcmd.c
+++ b/gdb/infcmd.c
@@ -3084,7 +3084,7 @@ environment to be given to the program."), &showlist);
 
   add_basic_prefix_cmd ("unset", no_class,
 			_("Complement to certain \"set\" commands."),
-			&unsetlist, "unset ", 0, &cmdlist);
+			&unsetlist, 0, &cmdlist);
 
   c = add_cmd ("environment", class_run, unset_environment_command, _("\
 Cancel environment variable VAR for the program.\n\
@@ -3121,7 +3121,7 @@ needed."),
 
   add_prefix_cmd ("kill", class_run, kill_command,
 		  _("Kill execution of program being debugged."),
-		  &killlist, "kill ", 0, &cmdlist);
+		  &killlist, 0, &cmdlist);
 
   add_com ("attach", class_run, attach_command, _("\
 Attach to a process or file outside of GDB.\n\
@@ -3140,7 +3140,7 @@ to specify the program, and to load its symbol table."));
 Detach a process or file previously attached.\n\
 If a process, it is no longer traced, and it continues its execution.  If\n\
 you were debugging a file, the file is closed and gdb no longer accesses it."),
-		  &detachlist, "detach ", 0, &cmdlist);
+		  &detachlist, 0, &cmdlist);
 
   add_com ("disconnect", class_run, disconnect_command, _("\
 Disconnect from a target.\n\
@@ -3295,7 +3295,7 @@ in the named register groups."));
 		  _("\
 Show additional information about a process.\n\
 Specify any process id, or use the program being debugged by default."),
-		  &info_proc_cmdlist, "info proc ",
+		  &info_proc_cmdlist,
 		  1/*allow-unknown*/, &infolist);
 
   add_cmd ("mappings", class_info, info_proc_cmd_mappings, _("\
diff --git a/gdb/language.c b/gdb/language.c
index 4cb71d6..a3f96ec 100644
--- a/gdb/language.c
+++ b/gdb/language.c
@@ -1166,13 +1166,13 @@ _initialize_language ()
 
   add_basic_prefix_cmd ("check", no_class,
 			_("Set the status of the type/range checker."),
-			&setchecklist, "set check ", 0, &setlist);
+			&setchecklist, 0, &setlist);
   add_alias_cmd ("c", "check", no_class, 1, &setlist);
   add_alias_cmd ("ch", "check", no_class, 1, &setlist);
 
   add_show_prefix_cmd ("check", no_class,
 		       _("Show the status of the type/range checker."),
-		       &showchecklist, "show check ", 0, &showlist);
+		       &showchecklist, 0, &showlist);
   add_alias_cmd ("c", "check", no_class, 1, &showlist);
   add_alias_cmd ("ch", "check", no_class, 1, &showlist);
 
diff --git a/gdb/macrocmd.c b/gdb/macrocmd.c
index d767926..4e4a68d 100644
--- a/gdb/macrocmd.c
+++ b/gdb/macrocmd.c
@@ -455,7 +455,7 @@ _initialize_macrocmd ()
      the various commands for working with preprocessor macros.  */
   add_basic_prefix_cmd ("macro", class_info,
 			_("Prefix for commands dealing with C preprocessor macros."),
-			&macrolist, "macro ", 0, &cmdlist);
+			&macrolist, 0, &cmdlist);
 
   add_cmd ("expand", no_class, macro_expand_command, _("\
 Fully expand any C/C++ preprocessor macro invocations in EXPRESSION.\n\
diff --git a/gdb/maint-test-options.c b/gdb/maint-test-options.c
index 16ecd1d..b773e75 100644
--- a/gdb/maint-test-options.c
+++ b/gdb/maint-test-options.c
@@ -422,8 +422,7 @@ _initialize_maint_test_options ()
 			_("\
 Generic command for testing the options infrastructure."),
 			&maintenance_test_options_list,
-			"maintenance test-options ", 0,
-			&maintenancelist);
+			0, &maintenancelist);
 
   const auto def_group = make_test_options_options_def_group (nullptr);
 
diff --git a/gdb/maint-test-settings.c b/gdb/maint-test-settings.c
index ca28fcf..0ce8890 100644
--- a/gdb/maint-test-settings.c
+++ b/gdb/maint-test-settings.c
@@ -89,7 +89,6 @@ _initialize_maint_test_settings ()
 			_("\
 Set GDB internal variables used for set/show command infrastructure testing."),
 			&maintenance_set_test_settings_list,
-			"maintenance set test-settings ",
 			0/*allow-unknown*/,
 			&maintenance_set_cmdlist);
 
@@ -97,7 +96,6 @@ Set GDB internal variables used for set/show command infrastructure testing."),
 		       _("\
 Show GDB internal variables used for set/show command infrastructure testing."),
 		       &maintenance_show_test_settings_list,
-		       "maintenance show test-settings ",
 		       0/*allow-unknown*/,
 		       &maintenance_show_cmdlist);
 
diff --git a/gdb/maint.c b/gdb/maint.c
index 7f505d0..154bef5 100644
--- a/gdb/maint.c
+++ b/gdb/maint.c
@@ -1137,14 +1137,14 @@ _initialize_maint_cmds ()
 Commands for use by GDB maintainers.\n\
 Includes commands to dump specific internal GDB structures in\n\
 a human readable form, to cause GDB to deliberately dump core, etc."),
-			&maintenancelist, "maintenance ", 0,
+			&maintenancelist, 0,
 			&cmdlist);
 
   add_com_alias ("mt", "maintenance", class_maintenance, 1);
 
   add_basic_prefix_cmd ("info", class_maintenance, _("\
 Commands for showing internal info about the program being debugged."),
-			&maintenanceinfolist, "maintenance info ", 0,
+			&maintenanceinfolist, 0,
 			&maintenancelist);
   add_alias_cmd ("i", "info", class_maintenance, 1, &maintenancelist);
 
@@ -1183,25 +1183,25 @@ sectoins."),
 
   add_basic_prefix_cmd ("print", class_maintenance,
 			_("Maintenance command for printing GDB internal state."),
-			&maintenanceprintlist, "maintenance print ", 0,
+			&maintenanceprintlist, 0,
 			&maintenancelist);
 
   add_basic_prefix_cmd ("flush", class_maintenance,
 			_("Maintenance command for flushing GDB internal caches."),
-			&maintenanceflushlist, "maintenance flush ", 0,
+			&maintenanceflushlist, 0,
 			&maintenancelist);
 
   add_basic_prefix_cmd ("set", class_maintenance, _("\
 Set GDB internal variables used by the GDB maintainer.\n\
 Configure variables internal to GDB that aid in GDB's maintenance"),
-			&maintenance_set_cmdlist, "maintenance set ",
+			&maintenance_set_cmdlist,
 			0/*allow-unknown*/,
 			&maintenancelist);
 
   add_show_prefix_cmd ("show", class_maintenance, _("\
 Show GDB internal variables used by the GDB maintainer.\n\
 Configure variables internal to GDB that aid in GDB's maintenance"),
-		       &maintenance_show_cmdlist, "maintenance show ",
+		       &maintenance_show_cmdlist,
 		       0/*allow-unknown*/,
 		       &maintenancelist);
 
@@ -1247,12 +1247,12 @@ This command has been moved to \"demangle\"."),
 
   add_prefix_cmd ("per-command", class_maintenance, set_per_command_cmd, _("\
 Per-command statistics settings."),
-		    &per_command_setlist, "maintenance set per-command ",
+		    &per_command_setlist,
 		    1/*allow-unknown*/, &maintenance_set_cmdlist);
 
   add_show_prefix_cmd ("per-command", class_maintenance, _("\
 Show per-command statistics settings."),
-		       &per_command_showlist, "maintenance show per-command ",
+		       &per_command_showlist,
 		       0/*allow-unknown*/, &maintenance_show_cmdlist);
 
   add_setshow_boolean_cmd ("time", class_maintenance,
@@ -1320,7 +1320,7 @@ Takes an optional file parameter."),
 
   add_basic_prefix_cmd ("check", class_maintenance, _("\
 Commands for checking internal gdb state."),
-			&maintenancechecklist, "maintenance check ", 0,
+			&maintenancechecklist, 0,
 			&maintenancelist);
 
   add_cmd ("translate-address", class_maintenance,
diff --git a/gdb/memattr.c b/gdb/memattr.c
index 17de583..e1c3931 100644
--- a/gdb/memattr.c
+++ b/gdb/memattr.c
@@ -625,11 +625,11 @@ Do \"info mem\" to see current list of IDs."), &deletelist);
 
   add_basic_prefix_cmd ("mem", class_vars, _("\
 Memory regions settings."),
-			&mem_set_cmdlist, "set mem ",
+			&mem_set_cmdlist,
 			0/* allow-unknown */, &setlist);
   add_show_prefix_cmd ("mem", class_vars, _("\
 Memory regions settings."),
-		       &mem_show_cmdlist, "show mem  ",
+		       &mem_show_cmdlist,
 		       0/* allow-unknown */, &showlist);
 
   add_setshow_boolean_cmd ("inaccessible-by-default", no_class,
diff --git a/gdb/mips-tdep.c b/gdb/mips-tdep.c
index 61545ae..2fe8332 100644
--- a/gdb/mips-tdep.c
+++ b/gdb/mips-tdep.c
@@ -8945,11 +8945,11 @@ _initialize_mips_tdep ()
   /* Add root prefix command for all "set mips"/"show mips" commands.  */
   add_basic_prefix_cmd ("mips", no_class,
 			_("Various MIPS specific commands."),
-			&setmipscmdlist, "set mips ", 0, &setlist);
+			&setmipscmdlist, 0, &setlist);
 
   add_show_prefix_cmd ("mips", no_class,
 		       _("Various MIPS specific commands."),
-		       &showmipscmdlist, "show mips ", 0, &showlist);
+		       &showmipscmdlist, 0, &showlist);
 
   /* Allow the user to override the ABI.  */
   add_setshow_enum_cmd ("abi", class_obscure, mips_abi_strings,
@@ -8990,7 +8990,7 @@ and is updated automatically from ELF file flags if available."),
 
   add_basic_prefix_cmd ("mipsfpu", class_support,
 			_("Set use of MIPS floating-point coprocessor."),
-			&mipsfpulist, "set mipsfpu ", 0, &setlist);
+			&mipsfpulist, 0, &setlist);
   add_cmd ("single", class_support, set_mipsfpu_single_command,
 	   _("Select single-precision MIPS floating-point coprocessor."),
 	   &mipsfpulist);
diff --git a/gdb/printcmd.c b/gdb/printcmd.c
index 1c68d19..a5c03c3 100644
--- a/gdb/printcmd.c
+++ b/gdb/printcmd.c
@@ -3281,7 +3281,7 @@ Use \"set variable\" for variables with names identical to set subcommands.\n\
 \n\
 With a subcommand, this command modifies parts of the gdb environment.\n\
 You can see these environment settings with the \"show\" command."),
-		  &setlist, "set ", 1, &cmdlist);
+		  &setlist, 1, &cmdlist);
   if (dbx_commands)
     add_com ("assign", class_vars, set_command, _("\
 Evaluate expression EXP and assign result to variable VAR.\n\
@@ -3385,7 +3385,7 @@ treat this string as a command line, and evaluate it."));
   /* Memory tagging commands.  */
   add_prefix_cmd ("memory-tag", class_vars, memory_tag_command, _("\
 Generic command for printing and manipulating memory tag properties."),
-		  &memory_tag_list, "memory-tag ", 0, &cmdlist);
+		  &memory_tag_list, 0, &cmdlist);
   add_cmd ("print-logical-tag", class_vars,
 	   memory_tag_print_logical_tag_command,
 	   ("Print the logical tag from POINTER.\n\
diff --git a/gdb/probe.c b/gdb/probe.c
index 0c4f22c..9eccf82 100644
--- a/gdb/probe.c
+++ b/gdb/probe.c
@@ -788,8 +788,7 @@ If you specify TYPE, there may be additional arguments needed by the\n\
 subcommand.\n\
 If you do not specify any argument, or specify `all', then the command\n\
 will show information about all types of probes."),
-		    &info_probes_cmdlist, "info probes ",
-		    0/*allow-unknown*/, &infolist);
+		    &info_probes_cmdlist, 0/*allow-unknown*/, &infolist);
 
   return &info_probes_cmdlist;
 }
diff --git a/gdb/python/py-cmd.c b/gdb/python/py-cmd.c
index f4d3dcc..9833bf8 100644
--- a/gdb/python/py-cmd.c
+++ b/gdb/python/py-cmd.c
@@ -95,9 +95,6 @@ cmdpy_destroyer (struct cmd_list_element *self, void *context)
   /* Release our hold on the command object.  */
   gdbpy_ref<cmdpy_object> cmd ((cmdpy_object *) context);
   cmd->command = NULL;
-
-  /* We may have allocated the prefix name.  */
-  xfree ((char *) self->prefixname);
 }
 
 /* Called by gdb to invoke the command.  */
@@ -114,7 +111,7 @@ cmdpy_function (struct cmd_list_element *command,
     error (_("Invalid invocation of Python command object."));
   if (! PyObject_HasAttr ((PyObject *) obj, invoke_cst))
     {
-      if (obj->command->prefixname)
+      if (obj->command->prefixlist != nullptr)
 	{
 	  /* A prefix command does not need an invoke method.  */
 	  return;
@@ -438,11 +435,11 @@ cmdpy_init (PyObject *self, PyObject *args, PyObject *kw)
   int completetype = -1;
   char *docstring = NULL;
   struct cmd_list_element **cmd_list;
-  char *cmd_name, *pfx_name;
+  char *cmd_name;
   static const char *keywords[] = { "name", "command_class", "completer_class",
 				    "prefix", NULL };
-  PyObject *is_prefix = NULL;
-  int cmp;
+  PyObject *is_prefix_obj = NULL;
+  bool is_prefix = false;
 
   if (obj->command)
     {
@@ -455,7 +452,7 @@ cmdpy_init (PyObject *self, PyObject *args, PyObject *kw)
 
   if (!gdb_PyArg_ParseTupleAndKeywords (args, kw, "si|iO",
 					keywords, &name, &cmdtype,
-					&completetype, &is_prefix))
+					&completetype, &is_prefix_obj))
     return -1;
 
   if (cmdtype != no_class && cmdtype != class_run
@@ -481,39 +478,17 @@ cmdpy_init (PyObject *self, PyObject *args, PyObject *kw)
   if (! cmd_name)
     return -1;
 
-  pfx_name = NULL;
-  if (is_prefix != NULL)
+  if (is_prefix_obj != NULL)
     {
-      cmp = PyObject_IsTrue (is_prefix);
-      if (cmp == 1)
-	{
-	  int i, out;
-	
-	  /* Make a normalized form of the command name.  */
-	  pfx_name = (char *) xmalloc (strlen (name) + 2);
-	
-	  i = 0;
-	  out = 0;
-	  while (name[i])
-	    {
-	      /* Skip whitespace.  */
-	      while (name[i] == ' ' || name[i] == '\t')
-		++i;
-	      /* Copy non-whitespace characters.  */
-	      while (name[i] && name[i] != ' ' && name[i] != '\t')
-		pfx_name[out++] = name[i++];
-	      /* Add a single space after each word -- including the final
-		 word.  */
-	      pfx_name[out++] = ' ';
-	    }
-	  pfx_name[out] = '\0';
-	}
-      else if (cmp < 0)
+      int cmp = PyObject_IsTrue (is_prefix_obj);
+       if (cmp < 0)
 	{
 	  xfree (cmd_name);
 	  return -1;
 	}
+       is_prefix = cmp > 0;
     }
+
   if (PyObject_HasAttr (self, gdbpy_doc_cst))
     {
       gdbpy_ref<> ds_obj (PyObject_GetAttr (self, gdbpy_doc_cst));
@@ -524,7 +499,6 @@ cmdpy_init (PyObject *self, PyObject *args, PyObject *kw)
 	  if (docstring == NULL)
 	    {
 	      xfree (cmd_name);
-	      xfree (pfx_name);
 	      return -1;
 	    }
 	}
@@ -538,7 +512,7 @@ cmdpy_init (PyObject *self, PyObject *args, PyObject *kw)
     {
       struct cmd_list_element *cmd;
 
-      if (pfx_name)
+      if (is_prefix)
 	{
 	  int allow_unknown;
 
@@ -547,7 +521,7 @@ cmdpy_init (PyObject *self, PyObject *args, PyObject *kw)
 	  allow_unknown = PyObject_HasAttr (self, invoke_cst);
 	  cmd = add_prefix_cmd (cmd_name, (enum command_class) cmdtype,
 				NULL, docstring, &obj->sub_list,
-				pfx_name, allow_unknown, cmd_list);
+				allow_unknown, cmd_list);
 	}
       else
 	cmd = add_cmd (cmd_name, (enum command_class) cmdtype,
@@ -571,7 +545,6 @@ cmdpy_init (PyObject *self, PyObject *args, PyObject *kw)
     {
       xfree (cmd_name);
       xfree (docstring);
-      xfree (pfx_name);
       gdbpy_convert_exception (except);
       return -1;
     }
diff --git a/gdb/python/python.c b/gdb/python/python.c
index c46d68b..4cea83c 100644
--- a/gdb/python/python.c
+++ b/gdb/python/python.c
@@ -1936,13 +1936,11 @@ This command is only a placeholder.")
   /* Add set/show python print-stack.  */
   add_basic_prefix_cmd ("python", no_class,
 			_("Prefix command for python preference settings."),
-			&user_show_python_list, "show python ", 0,
-			&showlist);
+			&user_show_python_list, 0, &showlist);
 
   add_show_prefix_cmd ("python", no_class,
 		       _("Prefix command for python preference settings."),
-		       &user_set_python_list, "set python ", 0,
-		       &setlist);
+		       &user_set_python_list, 0, &setlist);
 
   add_setshow_enum_cmd ("print-stack", no_class, python_excp_enums,
 			&gdbpy_should_print_stack, _("\
diff --git a/gdb/ravenscar-thread.c b/gdb/ravenscar-thread.c
index 84a0390..490af3a 100644
--- a/gdb/ravenscar-thread.c
+++ b/gdb/ravenscar-thread.c
@@ -719,11 +719,11 @@ _initialize_ravenscar ()
 
   add_basic_prefix_cmd ("ravenscar", no_class,
 			_("Prefix command for changing Ravenscar-specific settings."),
-			&set_ravenscar_list, "set ravenscar ", 0, &setlist);
+			&set_ravenscar_list, 0, &setlist);
 
   add_show_prefix_cmd ("ravenscar", no_class,
 		       _("Prefix command for showing Ravenscar-specific settings."),
-		       &show_ravenscar_list, "show ravenscar ", 0, &showlist);
+		       &show_ravenscar_list, 0, &showlist);
 
   add_setshow_boolean_cmd ("task-switching", class_obscure,
 			   &ravenscar_task_support, _("\
diff --git a/gdb/record-btrace.c b/gdb/record-btrace.c
index c888ad0..c04e1cd 100644
--- a/gdb/record-btrace.c
+++ b/gdb/record-btrace.c
@@ -3111,7 +3111,7 @@ _initialize_record_btrace ()
 {
   add_prefix_cmd ("btrace", class_obscure, cmd_record_btrace_start,
 		  _("Start branch trace recording."), &record_btrace_cmdlist,
-		  "record btrace ", 0, &record_cmdlist);
+		  0, &record_cmdlist);
   add_alias_cmd ("b", "btrace", class_obscure, 1, &record_cmdlist);
 
   add_cmd ("bts", class_obscure, cmd_record_btrace_bts_start,
@@ -3131,11 +3131,11 @@ This format may not be available on all processors."),
 
   add_basic_prefix_cmd ("btrace", class_support,
 			_("Set record options."), &set_record_btrace_cmdlist,
-			"set record btrace ", 0, &set_record_cmdlist);
+			0, &set_record_cmdlist);
 
   add_show_prefix_cmd ("btrace", class_support,
 		       _("Show record options."), &show_record_btrace_cmdlist,
-		       "show record btrace ", 0, &show_record_cmdlist);
+		       0, &show_record_cmdlist);
 
   add_setshow_enum_cmd ("replay-memory-access", no_class,
 			replay_memory_access_types, &replay_memory_access, _("\
@@ -3163,7 +3163,7 @@ When GDB does not support that cpu, this option can be used to enable\n\
 workarounds for a similar cpu that GDB supports.\n\n\
 When set to \"none\", errata workarounds are disabled."),
 		  &set_record_btrace_cpu_cmdlist,
-		  "set record btrace cpu ", 1,
+		  1,
 		  &set_record_btrace_cmdlist);
 
   add_cmd ("auto", class_support, cmd_set_record_btrace_cpu_auto, _("\
@@ -3181,13 +3181,13 @@ Show the cpu to be used for trace decode."),
   add_basic_prefix_cmd ("bts", class_support,
 			_("Set record btrace bts options."),
 			&set_record_btrace_bts_cmdlist,
-			"set record btrace bts ", 0,
+			0,
 			&set_record_btrace_cmdlist);
 
   add_show_prefix_cmd ("bts", class_support,
 		       _("Show record btrace bts options."),
 		       &show_record_btrace_bts_cmdlist,
-		       "show record btrace bts ", 0,
+		       0,
 		       &show_record_btrace_cmdlist);
 
   add_setshow_uinteger_cmd ("buffer-size", no_class,
@@ -3207,13 +3207,13 @@ The trace buffer size may not be changed while recording."), NULL,
   add_basic_prefix_cmd ("pt", class_support,
 			_("Set record btrace pt options."),
 			&set_record_btrace_pt_cmdlist,
-			"set record btrace pt ", 0,
+			0,
 			&set_record_btrace_cmdlist);
 
   add_show_prefix_cmd ("pt", class_support,
 		       _("Show record btrace pt options."),
 		       &show_record_btrace_pt_cmdlist,
-		       "show record btrace pt ", 0,
+		       0,
 		       &show_record_btrace_cmdlist);
 
   add_setshow_uinteger_cmd ("buffer-size", no_class,
diff --git a/gdb/record-full.c b/gdb/record-full.c
index 8a035b2..91da107 100644
--- a/gdb/record-full.c
+++ b/gdb/record-full.c
@@ -2794,7 +2794,7 @@ _initialize_record_full ()
 
   add_prefix_cmd ("full", class_obscure, cmd_record_full_start,
 		  _("Start full execution recording."), &record_full_cmdlist,
-		  "record full ", 0, &record_cmdlist);
+		  0, &record_cmdlist);
 
   c = add_cmd ("restore", class_obscure, cmd_record_full_restore,
 	       _("Restore the execution log from a file.\n\
@@ -2810,11 +2810,11 @@ Argument is filename.  File must be created with 'record save'."),
 
   add_basic_prefix_cmd ("full", class_support,
 			_("Set record options."), &set_record_full_cmdlist,
-			"set record full ", 0, &set_record_cmdlist);
+			0, &set_record_cmdlist);
 
   add_show_prefix_cmd ("full", class_support,
 		       _("Show record options."), &show_record_full_cmdlist,
-		       "show record full ", 0, &show_record_cmdlist);
+		       0, &show_record_cmdlist);
 
   /* Record instructions number limit command.  */
   add_setshow_boolean_cmd ("stop-at-limit", no_class,
diff --git a/gdb/record.c b/gdb/record.c
index 483b906..7dae18f 100644
--- a/gdb/record.c
+++ b/gdb/record.c
@@ -787,21 +787,21 @@ A size of \"unlimited\" means unlimited lines.  The default is 10."),
 
   c = add_prefix_cmd ("record", class_obscure, cmd_record_start,
 		      _("Start recording."),
-		      &record_cmdlist, "record ", 0, &cmdlist);
+		      &record_cmdlist, 0, &cmdlist);
   set_cmd_completer (c, filename_completer);
 
   add_com_alias ("rec", "record", class_obscure, 1);
   add_basic_prefix_cmd ("record", class_support,
 			_("Set record options."), &set_record_cmdlist,
-			"set record ", 0, &setlist);
+			0, &setlist);
   add_alias_cmd ("rec", "record", class_obscure, 1, &setlist);
   add_show_prefix_cmd ("record", class_support,
 		       _("Show record options."), &show_record_cmdlist,
-		       "show record ", 0, &showlist);
+		       0, &showlist);
   add_alias_cmd ("rec", "record", class_obscure, 1, &showlist);
   add_prefix_cmd ("record", class_support, info_record_command,
 		  _("Info record options."), &info_record_cmdlist,
-		  "info record ", 0, &infolist);
+		  0, &infolist);
   add_alias_cmd ("rec", "record", class_obscure, 1, &infolist);
 
   c = add_cmd ("save", class_obscure, cmd_record_save,
@@ -825,7 +825,7 @@ Default filename is 'gdb_record.PROCESS_ID'."),
   add_prefix_cmd ("goto", class_obscure, cmd_record_goto, _("\
 Restore the program to its state at instruction number N.\n\
 Argument is instruction number, as shown by 'info record'."),
-		  &record_goto_cmdlist, "record goto ", 1, &record_cmdlist);
+		  &record_goto_cmdlist, 1, &record_cmdlist);
 
   add_cmd ("begin", class_obscure, cmd_record_goto_begin,
 	   _("Go to the beginning of the execution log."),
diff --git a/gdb/remote.c b/gdb/remote.c
index d3a6659..8411b29 100644
--- a/gdb/remote.c
+++ b/gdb/remote.c
@@ -14854,13 +14854,13 @@ _initialize_remote ()
 Remote protocol specific variables.\n\
 Configure various remote-protocol specific variables such as\n\
 the packets being used."),
-			&remote_set_cmdlist, "set remote ",
+			&remote_set_cmdlist,
 			0 /* allow-unknown */, &setlist);
   add_prefix_cmd ("remote", class_maintenance, show_remote_cmd, _("\
 Remote protocol specific variables.\n\
 Configure various remote-protocol specific variables such as\n\
 the packets being used."),
-		  &remote_show_cmdlist, "show remote ",
+		  &remote_show_cmdlist,
 		  0 /* allow-unknown */, &showlist);
 
   add_cmd ("compare-sections", class_obscure, compare_sections_command, _("\
@@ -15282,7 +15282,7 @@ packets."),
   add_basic_prefix_cmd ("remote", class_files, _("\
 Manipulate files on the remote system.\n\
 Transfer files to and from the remote target system."),
-			&remote_cmdlist, "remote ",
+			&remote_cmdlist,
 			0 /* allow-unknown */, &cmdlist);
 
   add_cmd ("put", class_files, remote_put_command,
diff --git a/gdb/riscv-tdep.c b/gdb/riscv-tdep.c
index c178399..7fae914 100644
--- a/gdb/riscv-tdep.c
+++ b/gdb/riscv-tdep.c
@@ -3850,12 +3850,12 @@ _initialize_riscv_tdep ()
      riscv" commands.  */
   add_basic_prefix_cmd ("riscv", no_class,
 			_("RISC-V specific debug commands."),
-			&setdebugriscvcmdlist, "set debug riscv ", 0,
+			&setdebugriscvcmdlist, 0,
 			&setdebuglist);
 
   add_show_prefix_cmd ("riscv", no_class,
 		       _("RISC-V specific debug commands."),
-		       &showdebugriscvcmdlist, "show debug riscv ", 0,
+		       &showdebugriscvcmdlist, 0,
 		       &showdebuglist);
 
   add_setshow_zuinteger_cmd ("breakpoints", class_maintenance,
@@ -3901,11 +3901,11 @@ initialisation process."),
   /* Add root prefix command for all "set riscv" and "show riscv" commands.  */
   add_basic_prefix_cmd ("riscv", no_class,
 			_("RISC-V specific commands."),
-			&setriscvcmdlist, "set riscv ", 0, &setlist);
+			&setriscvcmdlist, 0, &setlist);
 
   add_show_prefix_cmd ("riscv", no_class,
 		       _("RISC-V specific commands."),
-		       &showriscvcmdlist, "show riscv ", 0, &showlist);
+		       &showriscvcmdlist, 0, &showlist);
 
 
   use_compressed_breakpoints = AUTO_BOOLEAN_AUTO;
diff --git a/gdb/rs6000-tdep.c b/gdb/rs6000-tdep.c
index 347014d..57dbe5b 100644
--- a/gdb/rs6000-tdep.c
+++ b/gdb/rs6000-tdep.c
@@ -7402,11 +7402,11 @@ _initialize_rs6000_tdep ()
      commands.  */
   add_basic_prefix_cmd ("powerpc", no_class,
 			_("Various PowerPC-specific commands."),
-			&setpowerpccmdlist, "set powerpc ", 0, &setlist);
+			&setpowerpccmdlist, 0, &setlist);
 
   add_show_prefix_cmd ("powerpc", no_class,
 		       _("Various PowerPC-specific commands."),
-		       &showpowerpccmdlist, "show powerpc ", 0, &showlist);
+		       &showpowerpccmdlist, 0, &showlist);
 
   /* Add a command to allow the user to force the ABI.  */
   add_setshow_auto_boolean_cmd ("soft-float", class_support,
diff --git a/gdb/ser-tcp.c b/gdb/ser-tcp.c
index e79c9e6..2519caa 100644
--- a/gdb/ser-tcp.c
+++ b/gdb/ser-tcp.c
@@ -469,12 +469,12 @@ _initialize_ser_tcp ()
   add_basic_prefix_cmd ("tcp", class_maintenance, _("\
 TCP protocol specific variables.\n\
 Configure variables specific to remote TCP connections."),
-			&tcp_set_cmdlist, "set tcp ",
+			&tcp_set_cmdlist,
 			0 /* allow-unknown */, &setlist);
   add_show_prefix_cmd ("tcp", class_maintenance, _("\
 TCP protocol specific variables.\n\
 Configure variables specific to remote TCP connections."),
-		       &tcp_show_cmdlist, "show tcp ",
+		       &tcp_show_cmdlist,
 		       0 /* allow-unknown */, &showlist);
 
   add_setshow_boolean_cmd ("auto-retry", class_obscure,
diff --git a/gdb/serial.c b/gdb/serial.c
index 1854721..719cd66 100644
--- a/gdb/serial.c
+++ b/gdb/serial.c
@@ -671,13 +671,13 @@ Use <CR>~. or <CR>~^D to break out."));
 
   add_basic_prefix_cmd ("serial", class_maintenance, _("\
 Set default serial/parallel port configuration."),
-			&serial_set_cmdlist, "set serial ",
+			&serial_set_cmdlist,
 			0/*allow-unknown*/,
 			&setlist);
 
   add_show_prefix_cmd ("serial", class_maintenance, _("\
 Show default serial/parallel port configuration."),
-		       &serial_show_cmdlist, "show serial ",
+		       &serial_show_cmdlist,
 		       0/*allow-unknown*/,
 		       &showlist);
 
diff --git a/gdb/sh-tdep.c b/gdb/sh-tdep.c
index 5a71d3a..31d912d 100644
--- a/gdb/sh-tdep.c
+++ b/gdb/sh-tdep.c
@@ -2415,9 +2415,9 @@ _initialize_sh_tdep ()
   gdbarch_register (bfd_arch_sh, sh_gdbarch_init, NULL);
 
   add_basic_prefix_cmd ("sh", no_class, "SH specific commands.",
-			&setshcmdlist, "set sh ", 0, &setlist);
+			&setshcmdlist, 0, &setlist);
   add_show_prefix_cmd ("sh", no_class, "SH specific commands.",
-		       &showshcmdlist, "show sh ", 0, &showlist);
+		       &showshcmdlist, 0, &showlist);
   
   add_setshow_enum_cmd ("calling-convention", class_vars, sh_cc_enum,
 			&sh_active_calling_convention,
diff --git a/gdb/skip.c b/gdb/skip.c
index eeb5715..4d24088 100644
--- a/gdb/skip.c
+++ b/gdb/skip.c
@@ -676,7 +676,7 @@ FILE-SPEC is one of:\n\
 FUNCTION-SPEC is one of:\n\
        -fu|-function FUNCTION-NAME\n\
        -rfu|-rfunction FUNCTION-NAME-REGULAR-EXPRESSION"),
-		  &skiplist, "skip ", 1, &cmdlist);
+		  &skiplist, 1, &cmdlist);
 
   c = add_cmd ("file", class_breakpoint, skip_file_command, _("\
 Ignore a file while stepping.\n\
diff --git a/gdb/sparc64-tdep.c b/gdb/sparc64-tdep.c
index 3609794..3f9600f 100644
--- a/gdb/sparc64-tdep.c
+++ b/gdb/sparc64-tdep.c
@@ -534,7 +534,7 @@ _initialize_sparc64_adi_tdep ()
 {
   add_basic_prefix_cmd ("adi", class_support,
 			_("ADI version related commands."),
-			&sparc64adilist, "adi ", 0, &cmdlist);
+			&sparc64adilist, 0, &cmdlist);
   add_cmd ("examine", class_support, adi_examine_command,
 	   _("Examine ADI versions."), &sparc64adilist);
   add_alias_cmd ("x", "examine", no_class, 1, &sparc64adilist);
diff --git a/gdb/stack.c b/gdb/stack.c
index bce6a2f..7856a5a 100644
--- a/gdb/stack.c
+++ b/gdb/stack.c
@@ -3343,7 +3343,7 @@ This is useful in command scripts."));
 Select and print a stack frame.\n\
 With no argument, print the selected stack frame.  (See also \"info frame\").\n\
 A single numerical argument specifies the frame to select."),
-		  &frame_cmd_list, "frame ", 1, &cmdlist);
+		  &frame_cmd_list, 1, &cmdlist);
   add_com_alias ("f", "frame", class_stack, 1);
 
 #define FRAME_APPLY_OPTION_HELP "\
@@ -3367,7 +3367,7 @@ With a negative COUNT argument, applies the command on outermost -COUNT frames.\
 
   cmd = add_prefix_cmd ("apply", class_stack, frame_apply_command,
 			frame_apply_cmd_help.c_str (),
-			&frame_apply_cmd_list, "frame apply ", 1,
+			&frame_apply_cmd_list, 1,
 			&frame_cmd_list);
   set_cmd_completer_handle_brkchars (cmd, frame_apply_cmd_completer);
 
@@ -3440,7 +3440,7 @@ Usage: frame level LEVEL"),
 		      &select_frame_cmd.base_command, _("\
 Select a stack frame without printing anything.\n\
 A single numerical argument specifies the frame to select."),
-		      &select_frame_cmd_list, "select-frame ", 1, &cmdlist,
+		      &select_frame_cmd_list, 1, &cmdlist,
 		      &cli_suppress_notification.user_selected_context);
 
   add_cmd_suppress_notification ("address", class_stack,
@@ -3515,7 +3515,7 @@ With a negative COUNT, print outermost -COUNT frames."),
 With no arguments, displays information about the currently selected stack\n\
 frame.  Alternatively a frame specification may be provided (See \"frame\")\n\
 the information is then printed about the specified frame."),
-		  &info_frame_cmd_list, "info frame ", 1, &infolist);
+		  &info_frame_cmd_list, 1, &infolist);
   add_info_alias ("f", "frame", 1);
 
   add_cmd ("address", class_stack, &info_frame_cmd.address,
diff --git a/gdb/symfile.c b/gdb/symfile.c
index 5defc22..4ba6953 100644
--- a/gdb/symfile.c
+++ b/gdb/symfile.c
@@ -3865,7 +3865,7 @@ on its own."), &cmdlist);
 
   add_basic_prefix_cmd ("overlay", class_support,
 			_("Commands for debugging overlays."), &overlaylist,
-			"overlay ", 0, &cmdlist);
+			0, &cmdlist);
 
   add_com_alias ("ovly", "overlay", class_support, 1);
   add_com_alias ("ov", "overlay", class_support, 1);
diff --git a/gdb/symtab.c b/gdb/symtab.c
index 061177e..9555f94 100644
--- a/gdb/symtab.c
+++ b/gdb/symtab.c
@@ -6799,8 +6799,7 @@ Options:\n\
 
   add_basic_prefix_cmd ("module", class_info, _("\
 Print information about modules."),
-			&info_module_cmdlist, "info module ",
-			0, &infolist);
+			&info_module_cmdlist, 0, &infolist);
 
   c = add_cmd ("functions", class_info, info_module_functions_command, _("\
 Display functions arranged by modules.\n\
diff --git a/gdb/target-descriptions.c b/gdb/target-descriptions.c
index 053864d..f7d0a68 100644
--- a/gdb/target-descriptions.c
+++ b/gdb/target-descriptions.c
@@ -1966,15 +1966,15 @@ _initialize_target_descriptions ()
 
   add_basic_prefix_cmd ("tdesc", class_maintenance, _("\
 Set target description specific variables."),
-			&tdesc_set_cmdlist, "set tdesc ",
+			&tdesc_set_cmdlist,
 			0 /* allow-unknown */, &setlist);
   add_show_prefix_cmd ("tdesc", class_maintenance, _("\
 Show target description specific variables."),
-		       &tdesc_show_cmdlist, "show tdesc ",
+		       &tdesc_show_cmdlist,
 		       0 /* allow-unknown */, &showlist);
   add_basic_prefix_cmd ("tdesc", class_maintenance, _("\
 Unset target description specific variables."),
-			&tdesc_unset_cmdlist, "unset tdesc ",
+			&tdesc_unset_cmdlist,
 			0 /* allow-unknown */, &unsetlist);
 
   add_setshow_filename_cmd ("filename", class_obscure,
diff --git a/gdb/target.c b/gdb/target.c
index 78327a2..438788e 100644
--- a/gdb/target.c
+++ b/gdb/target.c
@@ -872,7 +872,7 @@ The first argument is the type or protocol of the target machine.\n\
 Remaining arguments are interpreted by the target protocol.  For more\n\
 information on the arguments for a particular protocol, type\n\
 `help target ' followed by the protocol name."),
-			  &targetlist, "target ", 0, &cmdlist);
+			  &targetlist, 0, &cmdlist);
   c = add_cmd (t.shortname, no_class, t.doc, &targetlist);
   set_cmd_context (c, (void *) &t);
   set_cmd_sfunc (c, open_target);
diff --git a/gdb/thread.c b/gdb/thread.c
index fc6db96..3cd588e 100644
--- a/gdb/thread.c
+++ b/gdb/thread.c
@@ -2137,7 +2137,7 @@ Options:\n\
   add_prefix_cmd ("thread", class_run, thread_command, _("\
 Use this command to switch between threads.\n\
 The new thread ID must be currently known."),
-		  &thread_cmd_list, "thread ", 1, &cmdlist);
+		  &thread_cmd_list, 1, &cmdlist);
 
 #define THREAD_APPLY_OPTION_HELP "\
 Prints per-inferior thread number and target system's thread id\n\
@@ -2160,7 +2160,7 @@ THREAD_APPLY_OPTION_HELP),
 
   c = add_prefix_cmd ("apply", class_run, thread_apply_command,
 		      thread_apply_help.c_str (),
-		      &thread_apply_list, "thread apply ", 1,
+		      &thread_apply_list, 1,
 		      &thread_cmd_list);
   set_cmd_completer_handle_brkchars (c, thread_apply_command_completer);
 
diff --git a/gdb/top.c b/gdb/top.c
index a83d16b..2eb68fd 100644
--- a/gdb/top.c
+++ b/gdb/top.c
@@ -653,10 +653,14 @@ execute_command (const char *p, int from_tty)
 	   that can be followed by its args), report the list of
 	   subcommands.  */
 	{
+	  std::string prefixname = c->prefixname ();
+          std::string prefixname_no_space
+	    = prefixname.substr (0, prefixname.length () - 1);
 	  printf_unfiltered
-	    ("\"%.*s\" must be followed by the name of a subcommand.\n",
-	     (int) strlen (c->prefixname) - 1, c->prefixname);
-	  help_list (*c->prefixlist, c->prefixname, all_commands, gdb_stdout);
+	    ("\"%s\" must be followed by the name of a subcommand.\n",
+	     prefixname_no_space.c_str ());
+	  help_list (*c->prefixlist, prefixname.c_str (), all_commands,
+		     gdb_stdout);
 	}
       else if (c->type == set_cmd)
 	do_set_command (arg, from_tty, c);
diff --git a/gdb/tracepoint.c b/gdb/tracepoint.c
index 48d72d6..7f6d3e4 100644
--- a/gdb/tracepoint.c
+++ b/gdb/tracepoint.c
@@ -4046,7 +4046,7 @@ List target static tracepoints markers."));
   add_prefix_cmd ("tfind", class_trace, tfind_command, _("\
 Select a trace frame.\n\
 No argument means forward by one frame; '-' means backward by one frame."),
-		  &tfindlist, "tfind ", 1, &cmdlist);
+		  &tfindlist, 1, &cmdlist);
 
   add_cmd ("outside", class_trace, tfind_outside_command, _("\
 Select a trace frame whose PC is outside the given range (exclusive).\n\
diff --git a/gdb/tui/tui-layout.c b/gdb/tui/tui-layout.c
index bf9c3ff..b54e748 100644
--- a/gdb/tui/tui-layout.c
+++ b/gdb/tui/tui-layout.c
@@ -1022,7 +1022,7 @@ _initialize_tui_layout ()
   add_basic_prefix_cmd ("layout", class_tui, _("\
 Change the layout of windows.\n\
 Usage: layout prev | next | LAYOUT-NAME"),
-			&layout_list, "layout ", 0, &cmdlist);
+			&layout_list, 0, &cmdlist);
 
   add_cmd ("next", class_tui, tui_next_layout_command,
 	   _("Apply the next TUI layout."),
diff --git a/gdb/tui/tui-win.c b/gdb/tui/tui-win.c
index 17682b0..f036127 100644
--- a/gdb/tui/tui-win.c
+++ b/gdb/tui/tui-win.c
@@ -306,7 +306,7 @@ tui_get_cmd_list (void)
   if (tuilist == 0)
     add_basic_prefix_cmd ("tui", class_tui,
 			  _("Text User Interface commands."),
-			  &tuilist, "tui ", 0, &cmdlist);
+			  &tuilist, 0, &cmdlist);
   return &tuilist;
 }
 
@@ -996,12 +996,10 @@ _initialize_tui_win ()
      They will appear in the help list in the reverse of this order.  */
   add_basic_prefix_cmd ("tui", class_tui,
 			_("TUI configuration variables."),
-			&tui_setlist, "set tui ",
-			0 /* allow-unknown */, &setlist);
+			&tui_setlist, 0 /* allow-unknown */, &setlist);
   add_show_prefix_cmd ("tui", class_tui,
 		       _("TUI configuration variables."),
-		       &tui_showlist, "show tui ",
-		       0 /* allow-unknown */, &showlist);
+		       &tui_showlist, 0 /* allow-unknown */, &showlist);
 
   add_com ("refresh", class_tui, tui_refresh_all_command,
 	   _("Refresh the terminal display."));
diff --git a/gdb/typeprint.c b/gdb/typeprint.c
index eb47d91..0776f63 100644
--- a/gdb/typeprint.c
+++ b/gdb/typeprint.c
@@ -847,12 +847,10 @@ Only one level of typedefs is unrolled.  See also \"ptype\"."));
 
   add_show_prefix_cmd ("type", no_class,
 		       _("Generic command for showing type-printing settings."),
-		       &showprinttypelist, "show print type ", 0,
-		       &showprintlist);
+		       &showprinttypelist, 0, &showprintlist);
   add_basic_prefix_cmd ("type", no_class,
 			_("Generic command for setting how types print."),
-			&setprinttypelist, "set print type ", 0,
-			&setprintlist);
+			&setprinttypelist, 0, &setprintlist);
 
   add_setshow_boolean_cmd ("methods", no_class, &print_methods,
 			   _("\
diff --git a/gdb/unittests/command-def-selftests.c b/gdb/unittests/command-def-selftests.c
index e6aadf3..040e22b 100644
--- a/gdb/unittests/command-def-selftests.c
+++ b/gdb/unittests/command-def-selftests.c
@@ -87,7 +87,7 @@ check_doc (struct cmd_list_element *commandlist, const char *prefix)
 	{
 	  /* Recursively call ourselves on the subcommand list,
 	     passing the right prefix in.  */
-	  check_doc (*c->prefixlist, c->prefixname);
+	  check_doc (*c->prefixlist, c->prefixname ().c_str ());
 	}
     }
 }
@@ -159,7 +159,7 @@ traverse_command_structure (struct cmd_list_element **list,
 	{
 	  /* Recursively call ourselves on the subcommand list,
 	     passing the right prefix in.  */
-	  traverse_command_structure (c->prefixlist, c->prefixname);
+	  traverse_command_structure (c->prefixlist, c->prefixname ().c_str ());
 	}
       if (prefixcmd != c->prefix
 	  || (prefixcmd == nullptr && *list != cmdlist))
diff --git a/gdb/utils.c b/gdb/utils.c
index 1f48a5a..c59c635 100644
--- a/gdb/utils.c
+++ b/gdb/utils.c
@@ -506,14 +506,10 @@ add_internal_problem_command (struct internal_problem *problem)
 
   add_basic_prefix_cmd (problem->name, class_maintenance, set_doc,
 			set_cmd_list,
-			concat ("maintenance set ", problem->name, " ",
-				(char *) NULL),
 			0/*allow-unknown*/, &maintenance_set_cmdlist);
 
   add_show_prefix_cmd (problem->name, class_maintenance, show_doc,
 		       show_cmd_list,
-		       concat ("maintenance show ", problem->name, " ",
-			       (char *) NULL),
 		       0/*allow-unknown*/, &maintenance_show_cmdlist);
 
   if (problem->user_settable_should_quit)
diff --git a/gdb/valprint.c b/gdb/valprint.c
index 654552a..e191c35 100644
--- a/gdb/valprint.c
+++ b/gdb/valprint.c
@@ -3145,28 +3145,26 @@ _initialize_valprint ()
 
   add_basic_prefix_cmd ("print", no_class,
 			_("Generic command for setting how things print."),
-			&setprintlist, "set print ", 0, &setlist);
+			&setprintlist, 0, &setlist);
   add_alias_cmd ("p", "print", no_class, 1, &setlist);
   /* Prefer set print to set prompt.  */
   add_alias_cmd ("pr", "print", no_class, 1, &setlist);
 
   add_show_prefix_cmd ("print", no_class,
 		       _("Generic command for showing print settings."),
-		       &showprintlist, "show print ", 0, &showlist);
+		       &showprintlist, 0, &showlist);
   add_alias_cmd ("p", "print", no_class, 1, &showlist);
   add_alias_cmd ("pr", "print", no_class, 1, &showlist);
 
   cmd = add_basic_prefix_cmd ("raw", no_class,
 			      _("\
 Generic command for setting what things to print in \"raw\" mode."),
-			      &setprintrawlist, "set print raw ", 0,
-			      &setprintlist);
+			      &setprintrawlist, 0, &setprintlist);
   deprecate_cmd (cmd, nullptr);
 
   cmd = add_show_prefix_cmd ("raw", no_class,
 			     _("Generic command for showing \"print raw\" settings."),
-			     &showprintrawlist, "show print raw ", 0,
-			     &showprintlist);
+			     &showprintrawlist, 0, &showprintlist);
   deprecate_cmd (cmd, nullptr);
 
   gdb::option::add_setshow_cmds_for_options
diff --git a/gdb/value.c b/gdb/value.c
index 3bd81e7..9822cec 100644
--- a/gdb/value.c
+++ b/gdb/value.c
@@ -4259,7 +4259,7 @@ VARIABLE is already initialized."));
 
   add_prefix_cmd ("function", no_class, function_command, _("\
 Placeholder command for showing help on convenience functions."),
-		  &functionlist, "function ", 0, &cmdlist);
+		  &functionlist, 0, &cmdlist);
 
   add_internal_function ("_isvoid", _("\
 Check whether an expression is void.\n\
diff --git a/gdb/windows-tdep.c b/gdb/windows-tdep.c
index 97aa3da..e664484 100644
--- a/gdb/windows-tdep.c
+++ b/gdb/windows-tdep.c
@@ -616,7 +616,7 @@ init_w32_command_list (void)
       add_basic_prefix_cmd
 	("w32", class_info,
 	 _("Print information specific to Win32 debugging."),
-	 &info_w32_cmdlist, "info w32 ", 0, &infolist);
+	 &info_w32_cmdlist, 0, &infolist);
       w32_prefix_command_valid = 1;
     }
 }