[RFA,5/8] Allow defining a user command inside a user command

diff --git a/gdb/cli/cli-script.c b/gdb/cli/cli-script.c
index 36740b97ad..624a3bda68 100644
--- a/gdb/cli/cli-script.c
+++ b/gdb/cli/cli-script.c
@@ -44,6 +44,9 @@  recurse_read_control_structure (char * (*read_next_line_func) (void),
 				void (*validator)(char *, void *),
 				void *closure);
 
+static void do_define_command (const char *comname, int from_tty,
+			       const counted_command_line *commands);
+
 static char *read_next_line (void);
 
 /* Level of control structure when reading.  */
@@ -122,6 +125,7 @@  multi_line_command_p (enum command_control_type type)
     case compile_control:
     case python_control:
     case guile_control:
+    case define_control:
       return 1;
     default:
       return 0;
@@ -135,8 +139,9 @@  static struct command_line *
 build_command_line (enum command_control_type type, const char *args)
 {
   if ((args == NULL || *args == '\0')
-      && (type == if_control || type == while_control))
-    error (_("if/while commands require arguments."));
+      && (type == if_control || type == while_control
+	  || type == define_control))
+    error (_("if/while/define commands require arguments."));
   gdb_assert (args != NULL);
 
   return new struct command_line (type, xstrdup (args));
@@ -611,6 +616,12 @@  execute_control_command_1 (struct command_line *cmd)
       ret = simple_control;
       break;
 
+    case define_control:
+      print_command_trace ("define %s", cmd->line);
+      do_define_command (cmd->line, 0, &cmd->body_list_0);
+      ret = simple_control;
+      break;
+
     case python_control:
     case guile_control:
       {
@@ -960,6 +971,8 @@  process_next_line (char *p, struct command_line **command, int parse_commands,
 	{
 	  *command = build_command_line (commands_control, line_first_arg (p));
 	}
+      else if (command_name_equals (cmd, "define"))
+	*command = build_command_line (define_control, line_first_arg (p));
       else if (command_name_equals (cmd, "python") && !inline_cmd)
 	{
 	  /* Note that we ignore the inline "python command" form
@@ -1303,8 +1316,15 @@  user_defined_command (const char *ignore, int from_tty)
 {
 }
 
+/* Define a user-defined command.  If COMMANDS is NULL, then this is
+   an interactive call and the commands will be read from the user.
+   Otherwise, it is a "define" command in a script and the commands
+   are provided.  In the non-interactive case, various prompts and
+   warnings are disabled.  */
+
 static void
-define_command (const char *comname, int from_tty)
+do_define_command (const char *comname, int from_tty,
+		   const counted_command_line *commands)
 {
   enum cmd_hook_type
     {
@@ -1331,7 +1351,7 @@  define_command (const char *comname, int from_tty)
   if (c && strcmp (comname, c->name) != 0)
     c = 0;
 
-  if (c)
+  if (c && commands == nullptr)
     {
       int q;
 
@@ -1365,7 +1385,7 @@  define_command (const char *comname, int from_tty)
       hookc = lookup_cmd (&tem, *list, "", -1, 0);
       if (hookc && strcmp (comname + hook_name_size, hookc->name) != 0)
 	hookc = 0;
-      if (!hookc)
+      if (!hookc && commands == nullptr)
 	{
 	  warning (_("Your new `%s' command does not "
 		     "hook any existing command."),
@@ -1377,10 +1397,15 @@  define_command (const char *comname, int from_tty)
 
   comname = xstrdup (comname);
 
-  std::string prompt
-    = string_printf ("Type commands for definition of \"%s\".", comfull);
-  counted_command_line cmds = read_command_lines (prompt.c_str (), from_tty,
-						  1, 0, 0);
+  counted_command_line cmds;
+  if (commands == nullptr)
+    {
+      std::string prompt
+	= string_printf ("Type commands for definition of \"%s\".", comfull);
+      cmds = read_command_lines (prompt.c_str (), from_tty, 1, 0, 0);
+    }
+  else
+    cmds = *commands;
 
   newc = add_cmd (comname, class_user, user_defined_command,
 		  (c && c->theclass == class_user)
@@ -1410,6 +1435,12 @@  define_command (const char *comname, int from_tty)
 }
 
 static void
+define_command (const char *comname, int from_tty)
+{
+  do_define_command (comname, from_tty, nullptr);
+}
+
+static void
 document_command (const char *comname, int from_tty)
 {
   struct cmd_list_element *c, **list;
diff --git a/gdb/cli/cli-script.h b/gdb/cli/cli-script.h
index 7e5f94c0ad..0bd0d597ae 100644
--- a/gdb/cli/cli-script.h
+++ b/gdb/cli/cli-script.h
@@ -42,6 +42,7 @@  enum command_control_type
   compile_control,
   guile_control,
   while_stepping_control,
+  define_control,
   invalid_control
 };
 
diff --git a/gdb/testsuite/gdb.base/commands.exp b/gdb/testsuite/gdb.base/commands.exp
index b33e5124ec..f2f2b5d87c 100644
--- a/gdb/testsuite/gdb.base/commands.exp
+++ b/gdb/testsuite/gdb.base/commands.exp
@@ -1014,7 +1014,7 @@  proc_with_prefix redefine_backtrace_test {} {
 # Test using "if" and "while" without args when building a command list.
 
 proc define_if_without_arg_test {} {
-    foreach cmd {if while} {
+    foreach cmd {if while define} {
 	set test "define some_command_$cmd"
 	gdb_test_multiple $test $test {
 	    -re "End with"  {
@@ -1022,7 +1022,7 @@  proc define_if_without_arg_test {} {
 	    }
 	}
 
-	gdb_test "$cmd" "if/while commands require arguments." "type $cmd without args"
+	gdb_test "$cmd" "if/while/define commands require arguments." "type $cmd without args"
     }
 }
 
diff --git a/gdb/testsuite/gdb.base/define.exp b/gdb/testsuite/gdb.base/define.exp
index f82a9efdff..e4064b7afc 100644
--- a/gdb/testsuite/gdb.base/define.exp
+++ b/gdb/testsuite/gdb.base/define.exp
@@ -298,5 +298,13 @@  gdb_test_multiple "set prompt \\(gdb\\) " "reset gdb_prompt" {
     }
 }
 
+gdb_test_multiple "define do-define" "" {
+    -re "Type commands for definition of \"do-define\".\r\nEnd with a line saying just \"end\".\r\n>$" {
+	gdb_test "define do-printit\necho here\\n\nend\nend" "" "define do-define"
+    }
+}
+gdb_test_no_output "do-define" "invoke do-define"
+gdb_test "do-printit" "here" "invoke do-printit"
+
 gdb_exit
 return 0