diff --git a/racket/collects/compiler/private/xform.rkt b/racket/collects/compiler/private/xform.rkt
index fb5c26f33f..68fc0a6571 100644
--- a/racket/collects/compiler/private/xform.rkt
+++ b/racket/collects/compiler/private/xform.rkt
@@ -734,7 +734,7 @@
           (printf "#define RET_NOTHING { SET_GC_VARIABLE_STACK((void **)__gc_var_stack__[0]); return; }\n")
           ;; A non-value return inserted at the end of a void-returning function:
           (printf "#define RET_NOTHING_AT_END { SET_GC_VARIABLE_STACK((void **)__gc_var_stack__[0]); }\n")
-          
+
           ;; Declare a temp variable to hold the return value of the indicated type:
           (printf (if callee-restore?
                       "#define DECL_RET_SAVE(type) type __ret__val__;\n"
diff --git a/racket/src/racket/include/scheme.h b/racket/src/racket/include/scheme.h
index 0ce18ceaa9..4f2bd67220 100644
--- a/racket/src/racket/include/scheme.h
+++ b/racket/src/racket/include/scheme.h
@@ -252,11 +252,25 @@ extern "C"
 {
 #endif
 
-#if defined(MZ_DECLARE_NORETURN) && defined(__GNUC__)
-#define NORETURN __attribute__((__noreturn__))
+#if !defined(NORETURN)
+#if defined(__GNUC__) || defined(__clang__)
+#define NORETURN __attribute__((noreturn))
+#elif defined(_MSC_VER)
+#define NORETURN __declspec(noreturn)
 #else
 #define NORETURN
-#endif
+#endif /* defined(__GNUC__) || defined(__clang__) */
+#endif /* !defined(NORETURN) */
+
+#if !defined(UNREACHABLE)
+#if defined(__GNUC__) || defined(__clang__)
+#define UNREACHABLE __builtin_unreachable()
+#elif defined(_MSC_VER)
+#define UNREACHABLE __assume(0)
+#else
+#define UNREACHABLE
+#endif /* defined(__GNUC__) || defined(__clang__) */
+#endif /* !defined(NORETURN) */
 
 /* Allowed by all configurations, currently: */
 #define MZ_CAN_ACCESS_THREAD_LOCAL_DIRECTLY
@@ -1670,7 +1684,7 @@ MZ_EXTERN Scheme_Object *scheme_eval_waiting;
 #endif
 
 #ifdef MZ_USE_JIT
-MZ_EXTERN void scheme_jit_longjmp(mz_jit_jmp_buf b, int v);
+MZ_EXTERN NORETURN void scheme_jit_longjmp(mz_jit_jmp_buf b, int v);
 MZ_EXTERN void scheme_jit_setjmp_prepare(mz_jit_jmp_buf b);
 # define scheme_jit_setjmp(b) (scheme_jit_setjmp_prepare(b), scheme_call_mz_setjmp((b)->jb))
 #else
diff --git a/racket/src/racket/src/error.c b/racket/src/racket/src/error.c
index 1307fd616d..3d625fa419 100644
--- a/racket/src/racket/src/error.c
+++ b/racket/src/racket/src/error.c
@@ -90,7 +90,7 @@ static Scheme_Object *exe_yield_handler(int, Scheme_Object *[]);
 static Scheme_Object *error_print_width(int, Scheme_Object *[]);
 static Scheme_Object *error_print_context_length(int, Scheme_Object *[]);
 static Scheme_Object *error_print_srcloc(int, Scheme_Object *[]);
-static Scheme_Object *def_error_escape_proc(int, Scheme_Object *[]);
+static NORETURN void def_error_escape_proc(int, Scheme_Object *[]);
 static Scheme_Object *def_error_display_proc(int, Scheme_Object *[]);
 static Scheme_Object *emergency_error_display_proc(int, Scheme_Object *[]);
 static Scheme_Object *def_error_value_string_proc(int, Scheme_Object *[]);
@@ -115,7 +115,7 @@ static Scheme_Object *log_reader_p(int argc, Scheme_Object *argv[]);
 static int log_reader_get(Scheme_Object *ch, Scheme_Schedule_Info *sinfo);
 
 static NORETURN void do_raise(Scheme_Object *arg, int need_debug, int barrier);
-static Scheme_Object *nested_exn_handler(void *old_exn, int argc, Scheme_Object *argv[]);
+static NORETURN void nested_exn_handler(void *old_exn, int argc, Scheme_Object *argv[]);
 
 static void update_want_level(Scheme_Logger *logger, Scheme_Object *name);
 
@@ -227,7 +227,7 @@ Scheme_Config *scheme_init_error_escape_proc(Scheme_Config *config)
   if (!def_error_esc_proc) {
     REGISTER_SO(def_error_esc_proc);
     def_error_esc_proc =
-      scheme_make_prim_w_arity(def_error_escape_proc,
+      scheme_make_prim_w_arity((Scheme_Prim *)def_error_escape_proc,
 			       "default-error-escape-handler",
 			       0, 0);
   }
@@ -926,7 +926,7 @@ void scheme_init_logger_config() {
   scheme_set_root_param(MZCONFIG_LOGGER, (Scheme_Object *)scheme_main_logger);
 }
 
-static void
+static NORETURN void
 call_error(char *buffer, int len, Scheme_Object *exn)
 {
   if (scheme_current_thread->constant_folding) {
@@ -960,7 +960,7 @@ call_error(char *buffer, int len, Scheme_Object *exn)
     escape_handler = scheme_get_param(orig_config, MZCONFIG_ERROR_ESCAPE_HANDLER);
     
     v = scheme_make_byte_string_without_copying("error display handler");
-    v = scheme_make_closed_prim_w_arity(nested_exn_handler,
+    v = scheme_make_closed_prim_w_arity((Scheme_Closed_Prim *)nested_exn_handler,
 					scheme_make_pair(v, exn),
 					"nested-exception-handler", 
 					1, 1);
@@ -1000,7 +1000,7 @@ call_error(char *buffer, int len, Scheme_Object *exn)
     }
 
     v = scheme_make_byte_string_without_copying("error escape handler");
-    v = scheme_make_closed_prim_w_arity(nested_exn_handler,
+    v = scheme_make_closed_prim_w_arity((Scheme_Closed_Prim *)nested_exn_handler,
 					scheme_make_pair(v, exn),
 					"nested-exception-handler", 
 					1, 1);
@@ -3346,9 +3346,9 @@ def_error_value_string_proc(int argc, Scheme_Object *argv[])
   return scheme_make_sized_utf8_string(s, l);
 }
 
-static Scheme_Object *
+static NORETURN void
 def_error_escape_proc(int argc, Scheme_Object *argv[])
-{  
+{
   Scheme_Object *prompt;
   Scheme_Thread *p = scheme_current_thread;
 
@@ -3361,8 +3361,6 @@ def_error_escape_proc(int argc, Scheme_Object *argv[])
     p->cjs.val = scheme_void_proc;
   }
   scheme_longjmp(scheme_error_buf, 1);
-
-  return scheme_void; /* Never get here */
 }
 
 static Scheme_Object *
@@ -4405,7 +4403,7 @@ scheme_raise_exn(int id, ...)
            1);
 }
 
-static Scheme_Object *
+static NORETURN void
 def_exn_handler(int argc, Scheme_Object *argv[])
 {
   char *s;
@@ -4432,8 +4430,6 @@ def_exn_handler(int argc, Scheme_Object *argv[])
   }
 
   call_error(s, len, argv[0]);
-
-  return scheme_void;
 }
 
 static Scheme_Object *
@@ -4445,7 +4441,7 @@ init_exn_handler(int argc, Scheme_Object *argv[])
 			     1, NULL, NULL, 0);
 }
 
-static Scheme_Object *
+static NORETURN void
 nested_exn_handler(void *old_exn, int argc, Scheme_Object *argv[])
 {
   Scheme_Object *arg = argv[0], *orig_arg = SCHEME_CDR((Scheme_Object *)old_exn);
@@ -4496,13 +4492,11 @@ nested_exn_handler(void *old_exn, int argc, Scheme_Object *argv[])
 			msg, mlen,
 			orig_raisetype,
 			orig_msg, orig_mlen);
-    
-  call_error(buffer, blen, scheme_false);
 
-  return scheme_void;
+  call_error(buffer, blen, scheme_false);
 }
 
-static void *do_raise_inside_barrier(void)
+static NORETURN void *do_raise_inside_barrier(void)
 {
   Scheme_Object *arg;
   Scheme_Object *v, *p[1], *h, *marks;
@@ -4526,7 +4520,7 @@ static void *do_raise_inside_barrier(void)
     }
 
     v = scheme_make_byte_string_without_copying("exception handler");
-    v = scheme_make_closed_prim_w_arity(nested_exn_handler,
+    v = scheme_make_closed_prim_w_arity((Scheme_Closed_Prim *)nested_exn_handler,
                                         scheme_make_pair(v, arg),
                                         "nested-exception-handler", 
                                         1, 1);
@@ -4570,11 +4564,9 @@ static void *do_raise_inside_barrier(void)
     } else {
       /* return from uncaught-exception handler */
       p[0] = scheme_false;
-      return nested_exn_handler(scheme_make_pair(scheme_false, arg), 1, p);
+      nested_exn_handler(scheme_make_pair(scheme_false, arg), 1, p);
     }
   }
-
-  return scheme_void;
 }
 
 static void
@@ -4612,13 +4604,15 @@ do_raise(Scheme_Object *arg, int need_debug, int eb)
 
   p->ku.k.p1 = arg;
 
-  if (eb)
+  if (eb) {
     scheme_top_level_do(do_raise_inside_barrier, 1);
+    UNREACHABLE;
+  }
   else
     do_raise_inside_barrier();
 }
 
-static void
+static NORETURN void
 sch_raise(int argc, Scheme_Object *argv[])
 {
   if ((argc > 1) && SCHEME_FALSEP(argv[1]))
@@ -4781,7 +4775,7 @@ void scheme_init_exn_config(void)
 {
   Scheme_Object *h;
 
-  h = scheme_make_prim_w_arity(def_exn_handler, "default-exception-handler", 1, 1);
+  h = scheme_make_prim_w_arity((Scheme_Prim *)def_exn_handler, "default-exception-handler", 1, 1);
 
   scheme_set_root_param(MZCONFIG_INIT_EXN_HANDLER, h);
 }
diff --git a/racket/src/racket/src/makex.rkt b/racket/src/racket/src/makex.rkt
index e79b225d01..9468906cd0 100644
--- a/racket/src/racket/src/makex.rkt
+++ b/racket/src/racket/src/makex.rkt
@@ -62,6 +62,7 @@
                      [l (regexp-replace #rx"^XFORM_NONGCING " l "")]
                      [l (regexp-replace #rx"^XFORM_NONGCING_NONALIASING " l "")]
                      [l (regexp-replace #rx"^MZ_EXTERN " l "")]
+                     [l (regexp-replace #rx"^NORETURN " l "")]
                      [l (regexp-replace #rx"^THREAD_LOCAL " l "")]
                      [l2 (regexp-replace #rx"^volatile " l "")]
                      [volatile (if (equal? l l2) "" "volatile ")]
diff --git a/racket/src/racket/src/schemef.h b/racket/src/racket/src/schemef.h
index 418d35ed9c..99a09bd946 100644
--- a/racket/src/racket/src/schemef.h
+++ b/racket/src/racket/src/schemef.h
@@ -197,8 +197,8 @@ MZ_EXTERN Scheme_On_Atomic_Timeout_Proc scheme_set_on_atomic_timeout(Scheme_On_A
 /*                              error handling                            */
 /*========================================================================*/
 
-MZ_EXTERN void scheme_signal_error(const char *msg, ...) NORETURN;
-MZ_EXTERN void scheme_raise_exn(int exnid, ...) NORETURN;
+MZ_EXTERN NORETURN void scheme_signal_error(const char *msg, ...);
+MZ_EXTERN NORETURN void scheme_raise_exn(int exnid, ...);
 MZ_EXTERN void scheme_warning(char *msg, ...);
 
 MZ_EXTERN void scheme_raise(Scheme_Object *exn);
@@ -221,17 +221,17 @@ MZ_EXTERN void scheme_glib_log_message(const char *log_domain, int log_level, co
 MZ_EXTERN void *scheme_glib_log_message_test(char *str);
 MZ_EXTERN void scheme_out_of_memory_abort();
 
-MZ_EXTERN void scheme_wrong_count(const char *name, int minc, int maxc, int argc, Scheme_Object **argv) NORETURN;
-MZ_EXTERN void scheme_wrong_count_m(const char *name, int minc, int maxc, int argc, Scheme_Object **argv, int is_method) NORETURN;
-MZ_EXTERN void scheme_case_lambda_wrong_count(const char *name, int argc, Scheme_Object **argv, int is_method, int count, ...) NORETURN;
-MZ_EXTERN void scheme_wrong_type(const char *name, const char *expected, int which, int argc, Scheme_Object **argv) NORETURN;
-MZ_EXTERN void scheme_wrong_contract(const char *name, const char *expected, int which, int argc, Scheme_Object **argv) NORETURN;
-MZ_EXTERN void scheme_wrong_field_type(Scheme_Object *c_name, const char *expected, Scheme_Object *o) NORETURN;
-MZ_EXTERN void scheme_wrong_field_contract(Scheme_Object *c_name, const char *expected, Scheme_Object *o) NORETURN;
-MZ_EXTERN void scheme_arg_mismatch(const char *name, const char *msg, Scheme_Object *o) NORETURN;
-MZ_EXTERN void scheme_contract_error(const char *name, const char *msg, ...) NORETURN;
-MZ_EXTERN void scheme_wrong_return_arity(const char *where, int expected, int got, Scheme_Object **argv, const char *context_detail, ...) NORETURN;
-MZ_EXTERN void scheme_unbound_global(Scheme_Bucket *b) NORETURN;
+MZ_EXTERN NORETURN void scheme_wrong_count(const char *name, int minc, int maxc, int argc, Scheme_Object **argv);
+MZ_EXTERN NORETURN void scheme_wrong_count_m(const char *name, int minc, int maxc, int argc, Scheme_Object **argv, int is_method);
+MZ_EXTERN NORETURN void scheme_case_lambda_wrong_count(const char *name, int argc, Scheme_Object **argv, int is_method, int count, ...);
+MZ_EXTERN NORETURN void scheme_wrong_type(const char *name, const char *expected, int which, int argc, Scheme_Object **argv);
+MZ_EXTERN NORETURN void scheme_wrong_contract(const char *name, const char *expected, int which, int argc, Scheme_Object **argv);
+MZ_EXTERN NORETURN void scheme_wrong_field_type(Scheme_Object *c_name, const char *expected, Scheme_Object *o);
+MZ_EXTERN NORETURN void scheme_wrong_field_contract(Scheme_Object *c_name, const char *expected, Scheme_Object *o);
+MZ_EXTERN NORETURN void scheme_arg_mismatch(const char *name, const char *msg, Scheme_Object *o);
+MZ_EXTERN NORETURN void scheme_contract_error(const char *name, const char *msg, ...);
+MZ_EXTERN NORETURN void scheme_wrong_return_arity(const char *where, int expected, int got, Scheme_Object **argv, const char *context_detail, ...);
+MZ_EXTERN NORETURN void scheme_unbound_global(Scheme_Bucket *b);
 
 MZ_EXTERN Scheme_Object *scheme_dynamic_wind(void (*pre)(void *),
 					     Scheme_Object *(* volatile act)(void *),
diff --git a/racket/src/racket/src/schemex.h b/racket/src/racket/src/schemex.h
index 47cb5a8ae5..7f6a257b21 100644
--- a/racket/src/racket/src/schemex.h
+++ b/racket/src/racket/src/schemex.h
@@ -138,8 +138,8 @@ Scheme_On_Atomic_Timeout_Proc (*scheme_set_on_atomic_timeout)(Scheme_On_Atomic_T
 /*========================================================================*/
 /*                              error handling                            */
 /*========================================================================*/
-void (*scheme_signal_error)(const char *msg, ...) NORETURN;
-void (*scheme_raise_exn)(int exnid, ...) NORETURN;
+void (*scheme_signal_error)(const char *msg, ...);
+void (*scheme_raise_exn)(int exnid, ...);
 void (*scheme_warning)(char *msg, ...);
 void (*scheme_raise)(Scheme_Object *exn);
 int (*scheme_log_level_p)(Scheme_Logger *logger, int level);
@@ -159,17 +159,17 @@ void (*scheme_log_warning)(char *buffer);
 void (*scheme_glib_log_message)(const char *log_domain, int log_level, const char *message, void *user_data);
 void *(*scheme_glib_log_message_test)(char *str);
 void (*scheme_out_of_memory_abort)();
-void (*scheme_wrong_count)(const char *name, int minc, int maxc, int argc, Scheme_Object **argv) NORETURN;
-void (*scheme_wrong_count_m)(const char *name, int minc, int maxc, int argc, Scheme_Object **argv, int is_method) NORETURN;
-void (*scheme_case_lambda_wrong_count)(const char *name, int argc, Scheme_Object **argv, int is_method, int count, ...) NORETURN;
-void (*scheme_wrong_type)(const char *name, const char *expected, int which, int argc, Scheme_Object **argv) NORETURN;
-void (*scheme_wrong_contract)(const char *name, const char *expected, int which, int argc, Scheme_Object **argv) NORETURN;
-void (*scheme_wrong_field_type)(Scheme_Object *c_name, const char *expected, Scheme_Object *o) NORETURN;
-void (*scheme_wrong_field_contract)(Scheme_Object *c_name, const char *expected, Scheme_Object *o) NORETURN;
-void (*scheme_arg_mismatch)(const char *name, const char *msg, Scheme_Object *o) NORETURN;
-void (*scheme_contract_error)(const char *name, const char *msg, ...) NORETURN;
-void (*scheme_wrong_return_arity)(const char *where, int expected, int got, Scheme_Object **argv, const char *context_detail, ...) NORETURN;
-void (*scheme_unbound_global)(Scheme_Bucket *b) NORETURN;
+void (*scheme_wrong_count)(const char *name, int minc, int maxc, int argc, Scheme_Object **argv);
+void (*scheme_wrong_count_m)(const char *name, int minc, int maxc, int argc, Scheme_Object **argv, int is_method);
+void (*scheme_case_lambda_wrong_count)(const char *name, int argc, Scheme_Object **argv, int is_method, int count, ...);
+void (*scheme_wrong_type)(const char *name, const char *expected, int which, int argc, Scheme_Object **argv);
+void (*scheme_wrong_contract)(const char *name, const char *expected, int which, int argc, Scheme_Object **argv);
+void (*scheme_wrong_field_type)(Scheme_Object *c_name, const char *expected, Scheme_Object *o);
+void (*scheme_wrong_field_contract)(Scheme_Object *c_name, const char *expected, Scheme_Object *o);
+void (*scheme_arg_mismatch)(const char *name, const char *msg, Scheme_Object *o);
+void (*scheme_contract_error)(const char *name, const char *msg, ...);
+void (*scheme_wrong_return_arity)(const char *where, int expected, int got, Scheme_Object **argv, const char *context_detail, ...);
+void (*scheme_unbound_global)(Scheme_Bucket *b);
 Scheme_Object *(*scheme_dynamic_wind)(void (*pre)(void *),
 					     Scheme_Object *(* volatile act)(void *),
 					     void (* volatile post)(void *),
diff --git a/racket/src/racket/src/schpriv.h b/racket/src/racket/src/schpriv.h
index 4f9c730330..62c91be5a5 100644
--- a/racket/src/racket/src/schpriv.h
+++ b/racket/src/racket/src/schpriv.h
@@ -3392,7 +3392,7 @@ void scheme_rktio_error(const char *name, const char *what);
 
 void scheme_non_fixnum_result(const char *name, Scheme_Object *o);
 
-void scheme_raise_out_of_memory(const char *where, const char *msg, ...);
+NORETURN void scheme_raise_out_of_memory(const char *where, const char *msg, ...);
 
 char *scheme_make_srcloc_string(Scheme_Object *stx, intptr_t *len);