options: Complete the transition to numeric toggles (`#if') For the sake of review, this commit alters only the code; the affiliated comments within the source files also need to be updated, but doing so now would obscure the operational changes that have been made here. * All on/off options have been switched to the numeric `#if' variant; that is the only way to make this `default_options.h.in' thing work in a reasonable manner. * There is now some very minor compile-time checking of the user's choice of options. * NO_FAST_EXPTMOD doesn't seem to be used, so it has been removed. * ENABLE_USER_ALGO_LIST was supposed to be renamed DROPBEAR_USER_ALGO_LIST, and this commit completes that work. * DROPBEAR_FUZZ seems to be a relatively new, as-yet undocumented option, which was added by the following commit: commit 6e0b539e9ca0b5628c6c5a3d118ad6a2e79e8039 Author: Matt Johnston <[email protected]> Date: Tue May 23 22:29:21 2017 +0800 split out checkpubkey_line() separately It has now been added to `sysoptions.h' and defined as `0' by default. * The configuration option `DROPBEAR_PASSWORD_ENV' is no longer listed in `default_options.h.in'; it is no longer meant to be set by the user, and is instead left to be defined in `sysoptions.h' (where it was already being defined) as merely the name of the environment variable in question: DROPBEAR_PASSWORD To enable or disable use of that environment variable, the user must now toggle `DROPBEAR_USE_DROPBEAR_PASSWORD'. * The sFTP support is now toggled by setting `DROPBEAR_SFTPSERVER', and the path of the sFTP server program is set independently through the usual SFTPSERVER_PATH.

#include "options.h"
#include "dbutil.h"
#include "list.h"

void list_append(m_list *list, void *item) {
	m_list_elem *elem;
	
	elem = m_malloc(sizeof(*elem));
	elem->item = item;
	elem->list = list;
	elem->next = NULL;
	if (!list->first) {
		list->first = elem;
		elem->prev = NULL;
	} else {
		elem->prev = list->last;
		list->last->next = elem;
	}
	list->last = elem;
}

m_list * list_new() {
	m_list *ret = m_malloc(sizeof(m_list));
	ret->first = ret->last = NULL;
	return ret;
}

void * list_remove(m_list_elem *elem) {
	void *item = elem->item;
	m_list *list = elem->list;
	if (list->first == elem)
	{
		list->first = elem->next;
	}
	if (list->last == elem)
	{
		list->last = elem->prev;
	}
	if (elem->prev)
	{
		elem->prev->next = elem->next;
	}
	if (elem->next)
	{
		elem->next->prev = elem->prev;
	}
	m_free(elem);
	return item;
}