diff -r 5d5b72a71898 Include/pyport.h
--- a/Include/pyport.h	Tue Apr 24 14:44:18 2012 -0400
+++ b/Include/pyport.h	Tue Apr 24 15:10:30 2012 -0400
@@ -834,16 +834,26 @@ extern pid_t forkpty(int *, char *, stru
  * Specify alignment on compilers that support it.
  */
 #if defined(__GNUC__) && __GNUC__ >= 3
 #define Py_ALIGNED(x) __attribute__((aligned(x)))
 #else
 #define Py_ALIGNED(x)
 #endif
 
+#ifdef NDEBUG
+#ifdef __GNUC__
+#define Py_UNREACHABLE __builtin_unreachable()
+#else
+#define Py_UNREACHABLE Py_FatalError("reached unreachable code\n")
+#endif
+#else
+#define Py_UNREACHABLE assert(0)
+#endif
+
 /* Eliminate end-of-loop code not reached warnings from SunPro C
  * when using do{...}while(0) macros
  */
 #ifdef __SUNPRO_C
 #pragma error_messages (off,E_END_OF_LOOP_CODE_NOT_REACHED)
 #endif
 
 /*
diff -r 5d5b72a71898 Objects/dictobject.c
--- a/Objects/dictobject.c	Tue Apr 24 14:44:18 2012 -0400
+++ b/Objects/dictobject.c	Tue Apr 24 15:10:30 2012 -0400
@@ -510,18 +510,17 @@ lookdict(PyDictObject *mp, PyObject *key
                 PyErr_SetString(PyExc_RuntimeError,
                                 "dictionary changed size during lookup");
                 return NULL;
             }
         }
         else if (ep->me_key == dummy && freeslot == NULL)
             freeslot = ep;
     }
-    assert(0);          /* NOT REACHED */
-    return 0;
+    Py_UNREACHABLE;
 }
 
 /* Specialized version for string-only keys */
 static PyDictKeyEntry *
 lookdict_unicode(PyDictObject *mp, PyObject *key,
                  Py_hash_t hash, PyObject ***value_addr)
 {
     register size_t i;
diff -r 5d5b72a71898 Objects/unicodeobject.c
--- a/Objects/unicodeobject.c	Tue Apr 24 14:44:18 2012 -0400
+++ b/Objects/unicodeobject.c	Tue Apr 24 15:10:30 2012 -0400
@@ -626,20 +626,18 @@ Py_LOCAL_INLINE(Py_ssize_t) findchar(voi
             Py_UCS2 ch2 = (Py_UCS2) ch;
             if (ch2 == ch)
                 return ucs2lib_fastsearch((Py_UCS2 *) s, size, &ch2, 1, 0, mode);
             else
                 return -1;
         }
     case PyUnicode_4BYTE_KIND:
         return ucs4lib_fastsearch((Py_UCS4 *) s, size, &ch, 1, 0, mode);
-    default:
-        assert(0);
-        return -1;
-    }
+    }
+    Py_UNREACHABLE;
 }
 
 static PyObject*
 resize_compact(PyObject *unicode, Py_ssize_t length)
 {
     Py_ssize_t char_size;
     Py_ssize_t struct_size;
     Py_ssize_t new_size;
@@ -1981,18 +1979,17 @@ Py_UCS4
     switch(kind) {
     case PyUnicode_1BYTE_KIND:
         return ucs1lib_find_max_char(startptr, endptr);
     case PyUnicode_2BYTE_KIND:
         return ucs2lib_find_max_char(startptr, endptr);
     case PyUnicode_4BYTE_KIND:
         return ucs4lib_find_max_char(startptr, endptr);
     default:
-        assert(0);
-        return 0;
+        Py_UNREACHABLE;
     }
 }
 
 /* Ensure that a string uses the most efficient storage, if it is not the
    case: create a new string with of the right kind. Write NULL into *p_unicode
    on error. */
 static void
 unicode_adjust_maxchar(PyObject **p_unicode)