/*
 * The pty_signal_pipe, along with the SIGCHLD handler, must be
 * process-global rather than session-specific.
 */
static int pty_signal_pipe[2] = { -1, -1 };   /* obviously bogus initial val */

struct pty_tag {
    Config cfg;
    Conf *conf;
    int master_fd, slave_fd;
    void *frontend;
    char name[FILENAME_MAX];
    pid_t child_pid;
    int term_width, term_height;
    int child_dead, finished;
    int exit_code;

             * Attempt to send data down the pty.
             */
            pty_try_write(pty);
        }
    }

    if (finished && !pty->finished) {
	int close_on_exit;

	uxsel_del(pty->master_fd);
	pty_close(pty);
	pty->master_fd = -1;

	pty->finished = TRUE;

	/*
	 * This is a slight layering-violation sort of hack: only
	 * if we're not closing on exit (COE is set to Never, or to
	 * Only On Clean and it wasn't a clean exit) do we output a
	 * `terminated' message.
	 */
	close_on_exit = conf_get_int(pty->conf, CONF_close_on_exit);
	if (pty->cfg.close_on_exit == FORCE_OFF ||
	    (pty->cfg.close_on_exit == AUTO && pty->exit_code != 0)) {
	if (close_on_exit == FORCE_OFF ||
	    (close_on_exit == AUTO && pty->exit_code != 0)) {
	    char message[512];
	    if (WIFEXITED(pty->exit_code))
		sprintf(message, "\r\n[pterm: process terminated with exit"
			" code %d]\r\n", WEXITSTATUS(pty->exit_code));
	    else if (WIFSIGNALED(pty->exit_code))
#ifdef HAVE_NO_STRSIGNAL
		sprintf(message, "\r\n[pterm: process terminated on signal"

 * Called to set up the pty.
 * 
 * Returns an error message, or NULL on success.
 *
 * Also places the canonical host name into `realhost'. It must be
 * freed by the caller.
 */
static const char *pty_init(void *frontend, void **backend_handle, Config *cfg,
static const char *pty_init(void *frontend, void **backend_handle, Conf *conf,
			    char *host, int port, char **realhost, int nodelay,
			    int keepalive)
{
    int slavefd;
    pid_t pid, pgrp;
#ifndef NOT_X_WINDOWS		       /* for Mac OS X native compilation */
    long windowid;

	pty_stamped_utmp = FALSE;
#endif
    }

    pty->frontend = frontend;
    *backend_handle = NULL;	       /* we can't sensibly use this, sadly */

    pty->cfg = *cfg;		       /* structure copy */
    pty->term_width = cfg->width;
    pty->term_height = cfg->height;
    pty->conf = conf_copy(conf);
    pty->term_width = conf_get_int(conf, CONF_width);
    pty->term_height = conf_get_int(conf, CONF_height);

    if (pty->master_fd < 0)
	pty_open_master(pty);

    /*
     * Set the backspace character to be whichever of ^H and ^? is
     * specified by bksp_is_delete.
     */
    {
	struct termios attrs;
	tcgetattr(pty->master_fd, &attrs);
	attrs.c_cc[VERASE] = conf_get_int(conf, CONF_bksp_is_delete)
	attrs.c_cc[VERASE] = cfg->bksp_is_delete ? '\177' : '\010';
	    ? '\177' : '\010';
	tcsetattr(pty->master_fd, TCSANOW, &attrs);
    }

#ifndef OMIT_UTMP
    /*
     * Stamp utmp (that is, tell the utmp helper process to do so),
     * or not.
     */
    if (!cfg->stamp_utmp) {
    if (!conf_get_int(conf, CONF_stamp_utmp)) {
	close(pty_utmp_helper_pipe);   /* just let the child process die */
	pty_utmp_helper_pipe = -1;
    } else {
	char *location = get_x_display(pty->frontend);
	int len = strlen(location)+1, pos = 0;   /* +1 to include NUL */
	while (pos < len) {
	    int ret = write(pty_utmp_helper_pipe, location+pos, len - pos);

#endif
	pgrp = getpid();
	tcsetpgrp(0, pgrp);
	setpgid(pgrp, pgrp);
	close(open(pty->name, O_WRONLY, 0));
	setpgid(pgrp, pgrp);
	{
	    char *term_env_var = dupprintf("TERM=%s", cfg->termtype);
	    char *term_env_var = dupprintf("TERM=%s",
					   conf_get_str(conf, CONF_termtype));
	    putenv(term_env_var);
	    /* We mustn't free term_env_var, as putenv links it into the
	     * environment in place.
	     */
	}
#ifndef NOT_X_WINDOWS		       /* for Mac OS X native compilation */
	{
	    char *windowid_env_var = dupprintf("WINDOWID=%ld", windowid);
	    putenv(windowid_env_var);
	    /* We mustn't free windowid_env_var, as putenv links it into the
	     * environment in place.
	     */
	}
#endif
	{
	    char *e = cfg->environmt;
	    char *var, *varend, *val, *varval;
	    while (*e) {
	    char *key, *val;

	    for (val = conf_get_str_strs(conf, CONF_environmt, NULL, &key);
		var = e;
		while (*e && *e != '\t') e++;
		varend = e;
		if (*e == '\t') e++;
		val = e;
		 val != NULL;
		while (*e) e++;
		e++;

		varval = dupprintf("%.*s=%s", varend-var, var, val);
		 val = conf_get_str_strs(conf, CONF_environmt, key, &key)) {
		char *varval = dupcat(key, "=", val, NULL);
		putenv(varval);
		/*
		 * We must not free varval, since putenv links it
		 * into the environment _in place_. Weird, but
		 * there we go. Memory usage will be rationalised
		 * as soon as we exec anyway.
		 */

	putty_signal(SIGPIPE, SIG_DFL);
	block_signal(SIGCHLD, 0);
	if (pty_argv)
	    execvp(pty_argv[0], pty_argv);
	else {
	    char *shell = getenv("SHELL");
	    char *shellname;
	    if (cfg->login_shell) {
	    if (conf_get_int(conf, CONF_login_shell)) {
		char *p = strrchr(shell, '/');
		shellname = snewn(2+strlen(shell), char);
		p = p ? p+1 : shell;
		sprintf(shellname, "-%s", p);
	    } else
		shellname = shell;
	    execl(getenv("SHELL"), shellname, (void *)NULL);

    *backend_handle = pty;

    *realhost = dupprintf("\0");

    return NULL;
}

static void pty_reconfig(void *handle, Config *cfg)
static void pty_reconfig(void *handle, Conf *conf)
{
    Pty pty = (Pty)handle;
    /*
     * We don't have much need to reconfigure this backend, but
     * unfortunately we do need to pick up the setting of Close On
     * Exit so we know whether to give a `terminated' message.
     */
    pty->cfg = *cfg;		       /* structure copy */
    conf_copy_into(pty->conf, conf);
}

/*
 * Stub routine (never called in pterm).
 */
static void pty_free(void *handle)
{