--- realpath8.c	2020-11-22 17:52:17.586481571 -0500
+++ realpath9.c	2020-11-23 13:55:06.808458893 -0500
@@ -19,7 +19,7 @@
 	char *output = resolved ? resolved : buf;
 	size_t p, q, l, cnt=0;
 
-	l = strnlen(filename, sizeof stack + 1);
+	l = strnlen(filename, sizeof stack);
 	if (!l) {
 		errno = ENOENT;
 		return 0;
@@ -80,11 +80,16 @@
 			return 0;
 		}
 		if (k==p) goto toolong;
+		if (!k) {
+			errno = ENOENT;
+			return 0;
+		}
 		if (++cnt == SYMLOOP_MAX) {
 			errno = ELOOP;
 			return 0;
 		}
 		p -= k;
+		if (stack[k-1]=='/') p++;
 		memmove(stack+p, stack, k);
 	}
 
@@ -95,7 +100,8 @@
 		l = strlen(stack);
 		/* Cancel any initial .. components. */
 		p = 0;
-		while (q-p>=2 && at_dotdot(output+p+2, p+2)) {
+		while (output[p]=='.' && output[p+1]=='.'
+		  && (!output[p+2] || output[p+2]=='/')) {
 			while(l>1 && stack[l-1]!='/') l--;
 			if (l>1) l--;
 			p += 2;