loop condition is nonzero.  */voidwhile_command (char *arg, int from_tty){  struct command_line *command = NULL;  control_level = 1;  command = get_command_line (while_control, arg);  if (command == NULL)    return;  execute_control_command (command);  free_command_lines (&command);}/* "if" command support.  Execute either the true or false arm depending   on the value of the if conditional.  */voidif_command (char *arg, int from_tty){  struct command_line *command = NULL;  control_level = 1;  command = get_command_line (if_control, arg);  if (command == NULL)    return;  execute_control_command (command);  free_command_lines (&command);}/* Cleanup */static voidarg_cleanup (void *ignore){  struct user_args *oargs = user_args;  if (!user_args)    internal_error (__FILE__, __LINE__,		    "arg_cleanup called with no user args.\n");  user_args = user_args->next;  xfree (oargs);}/* Bind the incomming arguments for a user defined command to   $arg0, $arg1 ... $argMAXUSERARGS.  */static struct cleanup *setup_user_args (char *p){  struct user_args *args;  struct cleanup *old_chain;  unsigned int arg_count = 0;  args = (struct user_args *) xmalloc (sizeof (struct user_args));  memset (args, 0, sizeof (struct user_args));  args->next = user_args;  user_args = args;  old_chain = make_cleanup (arg_cleanup, 0/*ignored*/);  if (p == NULL)    return old_chain;  while (*p)    {      char *start_arg;      int squote = 0;      int dquote = 0;      int bsquote = 0;      if (arg_count >= MAXUSERARGS)	{	  error ("user defined function may only have %d arguments.\n",		 MAXUSERARGS);	  return old_chain;	}      /* Strip whitespace.  */      while (*p == ' ' || *p == '\t')	p++;      /* P now points to an argument.  */      start_arg = p;      user_args->a[arg_count].arg = p;      /* Get to the end of this argument.  */      while (*p)	{	  if (((*p == ' ' || *p == '\t')) && !squote && !dquote && !bsquote)	    break;	  else	    {	      if (bsquote)		bsquote = 0;	      else if (*p == '\\')		bsquote = 1;	      else if (squote)		{		  if (*p == '\'')		    squote = 0;		}	      else if (dquote)		{		  if (*p == '"')		    dquote = 0;		}	      else		{		  if (*p == '\'')		    squote = 1;		  else if (*p == '"')		    dquote = 1;		}	      p++;	    }	}      user_args->a[arg_count].len = p - start_arg;      arg_count++;      user_args->count++;    }  return old_chain;}/* Given character string P, return a point to the first argument ($arg),   or NULL if P contains no arguments.  */static char *locate_arg (char *p){  while ((p = strchr (p, '$')))    {      if (strncmp (p, "$arg", 4) == 0 && isdigit (p[4]))	return p;      p++;    }  return NULL;}/* Insert the user defined arguments stored in user_arg into the $arg   arguments found in line, with the updated copy being placed into nline.  */static char *insert_args (char *line){  char *p, *save_line, *new_line;  unsigned len, i;  /* First we need to know how much memory to allocate for the new line.  */  save_line = line;  len = 0;  while ((p = locate_arg (line)))    {      len += p - line;      i = p[4] - '0';      if (i >= user_args->count)	{	  error ("Missing argument %d in user function.\n", i);	  return NULL;	}      len += user_args->a[i].len;      line = p + 5;    }  /* Don't forget the tail.  */  len += strlen (line);  /* Allocate space for the new line and fill it in.  */  new_line = (char *) xmalloc (len + 1);  if (new_line == NULL)    return NULL;  /* Restore pointer to beginning of old line.  */  line = save_line;  /* Save pointer to beginning of new line.  */  save_line = new_line;  while ((p = locate_arg (line)))    {      int i, len;      memcpy (new_line, line, p - line);      new_line += p - line;      i = p[4] - '0';      len = user_args->a[i].len;      if (len)	{	  memcpy (new_line, user_args->a[i].arg, len);	  new_line += len;	}      line = p + 5;    }  /* Don't forget the tail.  */  strcpy (new_line, line);  /* Return a pointer to the beginning of the new line.  */  return save_line;}/* Expand the body_list of COMMAND so that it can hold NEW_LENGTH   code bodies.  This is typically used when we encounter an "else"   clause for an "if" command.  */static voidrealloc_body_list (struct command_line *command, int new_length){  int n;  struct command_line **body_list;  n = command->body_count;  /* Nothing to do?  */  if (new_length <= n)    return;  body_list = (struct command_line **)    xmalloc (sizeof (struct command_line *) * new_length);  memcpy (body_list, command->body_list, sizeof (struct command_line *) * n);  xfree (command->body_list);  command->body_list = body_list;  command->body_count = new_length;}/* Read one line from the input stream.  If the command is an "else" or   "end", return such an indication to the caller.  */static enum misc_command_typeread_next_line (struct command_line **command){  char *p, *p1, *prompt_ptr, control_prompt[256];  int i = 0;  if (control_level >= 254)    error ("Control nesting too deep!\n");  /* Set a prompt based on the nesting of the control commands.  */  if (instream == stdin || (instream == 0 && deprecated_readline_hook != NULL))    {      for (i = 0; i < control_level; i++)	control_prompt[i] = ' ';      control_prompt[i] = '>';      control_prompt[i + 1] = '\0';      prompt_ptr = (char *) &control_prompt[0];    }  else    prompt_ptr = NULL;  p = command_line_input (prompt_ptr, instream == stdin, "commands");  /* Not sure what to do here.  */  if (p == NULL)    return end_command;  /* Strip leading and trailing whitespace.  */  while (*p == ' ' || *p == '\t')    p++;  p1 = p + strlen (p);  while (p1 != p && (p1[-1] == ' ' || p1[-1] == '\t'))    p1--;  /* Blanks and comments don't really do anything, but we need to     distinguish them from else, end and other commands which can be     executed.  */  if (p1 == p || p[0] == '#')    return nop_command;  /* Is this the end of a simple, while, or if control structure?  */  if (p1 - p == 3 && !strncmp (p, "end", 3))    return end_command;  /* Is the else clause of an if control structure?  */  if (p1 - p == 4 && !strncmp (p, "else", 4))    return else_command;  /* Check for while, if, break, continue, etc and build a new command     line structure for them.  */  if (p1 - p > 5 && !strncmp (p, "while", 5))    {      char *first_arg;      first_arg = p + 5;      while (first_arg < p1 && isspace (*first_arg))        first_arg++;      *command = build_command_line (while_control, first_arg);    }  else if (p1 - p > 2 && !strncmp (p, "if", 2))    {      char *first_arg;      first_arg = p + 2;      while (first_arg < p1 && isspace (*first_arg))        first_arg++;      *command = build_command_line (if_control, first_arg);    }  else if (p1 - p == 10 && !strncmp (p, "loop_break", 10))    {      *command = (struct command_line *)	xmalloc (sizeof (struct command_line));      (*command)->next = NULL;      (*command)->line = NULL;      (*command)->control_type = break_control;      (*command)->body_count = 0;      (*command)->body_list = NULL;    }  else if (p1 - p == 13 && !strncmp (p, "loop_continue", 13))    {      *command = (struct command_line *)	xmalloc (sizeof (struct command_line));      (*command)->next = NULL;      (*command)->line = NULL;      (*command)->control_type = continue_control;      (*command)->body_count = 0;      (*command)->body_list = NULL;    }  else    {      /* A normal command.  */      *command = (struct command_line *)	xmalloc (sizeof (struct command_line));      (*command)->next = NULL;      (*command)->line = savestring (p, p1 - p);      (*command)->control_type = simple_control;      (*command)->body_count = 0;      (*command)->body_list = NULL;    }  /* Nothing special.  */  return ok_command;}/* Recursively read in the control structures and create a command_line    structure from them.   The parent_control parameter is the control structure in which the   following commands are nested.  */static enum command_control_typerecurse_read_control_structure (struct command_line *current_cmd){  int current_body, i;  enum misc_command_type val;  enum command_control_type ret;  struct command_line **body_ptr, *child_tail, *next;  child_tail = NULL;  current_body = 1;  /* Sanity checks.  */  if (current_cmd->control_type == simple_control)    {      error ("Recursed on a simple control type\n");      return invalid_control;    }  if (current_body > current_cmd->body_count)    {      error ("Allocated body is smaller than this command type needs\n");      return invalid_control;    }  /* Read lines from the input stream and build control structures.  */  while (1)    {      dont_repeat ();      next = NULL;      val = read_next_line (&next);      /* Just skip blanks and comments.  */      if (val == nop_command)	continue;      if (val == end_command)	{	  if (current_cmd->control_type == while_control	      || current_cmd->control_type == if_control)	    {	      /* Success reading an entire control structure.  */	      ret = simple_control;	      break;	    }	  else	    {	      ret = invalid_control;	      break;	    }	}      /* Not the end of a control structure.  */      if (val == else_command)	{	  if (current_cmd->control_type == if_control	      && current_body == 1)	    {	      realloc_body_list (current_cmd, 2);	      current_body = 2;	      child_tail = NULL;	      continue;	    }	  else	    {	      ret = invalid_control;	      break;	    }	}      if (child_tail)	{	  child_tail->next = next;	}      else	{	  body_ptr = current_cmd->body_list;	  for (i = 1; i < current_body; i++)	    body_ptr++;	  *body_ptr = next;	}      child_tail = next;      /* If the latest line is another control structure, then recurse         on it.  */      if (next->control_type == while_control	  || next->control_type == if_control)	{	  control_level++;