tb Implement a string stack

ulib/linklist.h

@@ -68,4 +68,16 @@
        var != NULL && (idx) < (max); \
        var = tmp, tmp = (var ? var->next : NULL), (idx)++)
 
+#define LL_BACK(head, out) \
+  do { \
+    (out) = NULL; \
+    if ((head) != NULL) { \
+      typeof((head)) __tmp = (head); \
+      while (__tmp->next != NULL) { \
+        __tmp = __tmp->next; \
+      } \
+      (out) = __tmp; \
+    } \
+  } while(0)
+
 #endif // ULIB_LINKLIST_H_