diff --git a/include/ucore/backtrace.h b/include/ucore/backtrace.h
index d1c43d5..41afcde 100644
--- a/include/ucore/backtrace.h
+++ b/include/ucore/backtrace.h
@@ -1,12 +1,14 @@
 #ifndef UC_BACKTRACE_H_
 #define UC_BACKTRACE_H_
 #include <stddef.h>
+#include <stdlib.h>
+#include "utils.h"
 
 #ifdef __cplusplus
 extern "C" {
 #endif
 
-#define UC_BACTRACE_STDERR uc_backtrace_fd(2)
+#define UC_BACKTRACE_STDERR uc_backtrace_fd(2)
 /**
  * Print a stacktrace to the given file descriptor.
  *
@@ -24,6 +26,30 @@ void uc_backtrace_fd(int fd);
  */
 void uc_backtrace_buf(char *buf, size_t len);
 
+/** 
+ * assert() that is not affected by NDEBUG define
+ */
+#define UC_ASSERT(expr)\
+ do {\
+    if (!(expr) ) {\
+        fprintf(stderr,\
+        "UC_ASSERT failed '%s' %s\n", UC_STRINGIFY(expr), UC_SRC_LOCATION);\
+        UC_BACKTRACE_STDERR;\
+        abort();\
+    }\
+} while (0)
+
+/** 
+ * Macro for asserting code that should not be reached, 
+ * terminates the program if executed
+ */
+#define UC_NOT_REACED()\
+do {\
+    fprintf(stderr, "UC_NOT_REACHED at %s\n", UC_SRC_LOCATION);\
+    UC_BACKTRACE_STDERR;\
+    abort();\
+while (0)
+
 #ifdef __cplusplus
 }
 #endif
diff --git a/include/ucore/utils.h b/include/ucore/utils.h
index 39db850..e2b6592 100644
--- a/include/ucore/utils.h
+++ b/include/ucore/utils.h
@@ -3,8 +3,6 @@
 
 #include <stddef.h>
 #include <stdio.h>
-#include <stdlib.h>
-#include "backtrace.h"
 
 //Gnerate a compiler error if the compile time
 //constant expression fails
@@ -75,18 +73,6 @@ const typeof( ((const type *)0)->member ) *__mptr = (ptr);    \
  */
 #define UC_SRC_LOCATION __FILE__ ":" UC_STRINGIFY(__LINE__)
 
-/** 
- * assert() that is not affected by NDEBUG define
- */
-#define UC_ASSERT(expr)\
- do {\
-    if (!(expr) ) {\
-        fprintf(stderr,\
-        "UC_ASSERT failed '%s' %s\n", UC_STRINGIFY(expr), UC_SRC_LOCATION);\
-        uc_backtrace_fd(2);\
-        abort();\
-    }\
-} while (0)
 
 #ifdef DEBUG
     #define TRACEF(fmt, ...)\
@@ -98,17 +84,6 @@ const typeof( ((const type *)0)->member ) *__mptr = (ptr);    \
     #define TRACEF(fmt, ...) do {} while(0)
 #endif
 
-/** 
- * Macro for asserting code that should not be reached, 
- * terminates the program if executed
- */
-#define UC_NOT_REACED()\
-do {\
-    fprintf(stderr, "UC_NOT_REACED at %s\n", UC_SRC_LOCATION);\
-    uc_backtrace_fd(2);\
-    abort();\
-while (0)
-
 /**
  * Round up x / y
  * (e.g 100/9 == 12, 3/2 == 2)
@@ -138,6 +113,9 @@ while (0)
  */
 #define UC_ROUND_DOWN(x, y) ((x) / (y) * (y))
 
+/** Indicate the variable is unused.
+ */
+#define UC_UNUSED(x) x __attribute__((unused))
 
 #endif
 
diff --git a/test/test_dstr.c b/test/test_dstr.c
index 6168e98..926239c 100644
--- a/test/test_dstr.c
+++ b/test/test_dstr.c
@@ -1,4 +1,5 @@
 #include <check.h>
+#include <stdlib.h>
 #include <ctype.h>
 #include <ucore/dstr.h>
 #include <ucore/utils.h>