      return memcpy(to, from, size);
  }
  
-@@ -39,32 +39,26 @@
+@@ -39,32 +41,26 @@
   */
  #define memcpy_check( d, s, n )                                             \
    do {                                                                      \

 #define inclusive_range_check( low, n, high )   \
   do  {                                         \
     __typeof( n ) __tmp_n = ( n );              \
@@ -78,7 +72,7 @@
     lt_check(__tmp_n, high);                    \
   } while (0)
 
-#define GUARD( x )      if ( (x) < 0 ) return -1
+#define GUARD( x ) __VERIFIER_assume( (x) >= 0 )
 #define GUARD_PTR( x )  if ( (x) < 0 ) return NULL
 
 /**

--- ../../../../../utils/s2n_safety.h	2018-02-27 12:04:53.000000000 -0500
+++ s2n_safety.h	2018-02-27 12:17:14.000000000 -0500
@@ -15,23 +15,25 @@
 
 #pragma once
 
