Index: xpriv.c
==================================================================
--- xpriv.c
+++ xpriv.c
@@ -36,10 +36,20 @@
  * window’s  ID from  the $WINDOWID  environment variable
  * which urxvt  sets. after this, a  ssh-agent process is
  * launched. spriv waits until it has opened a socket and
  * then runs ssh-add without parameters to add the user's
  * default keys to the session.
+ *
+ * after  a success  key-add  has  been confirmed,  xpriv
+ * marks the window as “vital”  by setting the X property
+ * “_k_vital” on the  window. if the login  fails or does
+ * not complete,  safekill.c will  still terminate  it at
+ * any time.  the vital  flag is removed  as soon  as the
+ * controlling shell terminates; it does *not* remain for
+ * the lifetime  of the window, so  a "temporary" session
+ * can  be created  in  the current  terminal by  calling
+ * `xpriv -a` directly.
  *
  * xpriv  does  its  best   to  clean  up  after  itself,
  * killing all sensitive processes and their children and
  * removing the  shmem segment  when it  is no  longer in
  * use, even if exits somewhat abnormally. if you have to
@@ -306,11 +316,11 @@
 		}
 		if(opt[1] != 0) { ++opt; goto read_opt; }
 	}
 
 	size_t nsz;
-	const char* basename, *p;
+	const char* basename = argv[0], *p;
 	for (p = argv[0]; *p!=0; ++p) {
 		if(*p == '/') basename = p + 1;
 	}
 	nsz = p - basename;
 	char shid[nsz + sizeof shmem_prefix + 0];