--- sfwrite.c	2000/09/20 21:07:26	1.1
+++ sfwrite.c	2000/09/20 21:08:44	1.2
@@ -100,6 +100,8 @@
 		else
 		{	if(w > (ssize_t)n)
 				w = (ssize_t)n;
+			if(w <= 0) /* no forward progress possible */
+				break;
 			memcpy(f->next, s, w);
 			f->next += w;
 		}