diff --git a/src/string.h b/src/string.h
index 43695a9..45cd206 100644
--- a/src/string.h
+++ b/src/string.h
@@ -1,8 +1,8 @@
 #pragma once
-#include "types.h"
 #include "atrb.h"
+#include "types.h"
 
-int   memcmp(const void *s1, const void *s2, usize n);
-void *memset(void *s, int c, usize n);
-void *memcpy(void *restrict dst, const void *restrict src, usize n);
-void *memmove(void *dst, const void *src, usize n);
+int   memcmp(const void *s1, const void *s2, usize n) NONNULL((1, 2)) PURE;
+void *memset(void *s, int c, usize n) NONNULL((1));
+void *memcpy(void *restrict dst, const void *restrict src, usize n) NONNULL((1, 2));
+void *memmove(void *dst, const void *src, usize n) NONNULL((1, 2));