Index: encoding.c
===================================================================
--- encoding.c	(revision 34755)
+++ encoding.c	(working copy)
@@ -911,6 +911,8 @@ rb_enc_codepoint_len(const char *p, cons
     }
     else
 	rb_raise(rb_eArgError, "invalid byte sequence in %s", rb_enc_name(enc));
+
+    return 0; /* not reached */
 }
 
 #undef rb_enc_codepoint
Index: re.c
===================================================================
--- re.c	(revision 34755)
+++ re.c	(working copy)
@@ -1665,6 +1665,8 @@ name_to_backref_number(struct re_registe
 	rb_raise(rb_eIndexError, "undefined group name reference: %s",
 				 StringValuePtr(s));
     }
+
+    return 0; /* not reached */
 }
 
 /*
Index: object.c
===================================================================
--- object.c	(revision 34755)
+++ object.c	(working copy)
@@ -2470,6 +2470,8 @@ rb_Float(VALUE val)
       default:
 	return rb_convert_type(val, T_FLOAT, "Float", "to_f");
     }
+
+    return Qnil; /* not reached */
 }
 
 /*
Index: io.c
===================================================================
--- io.c	(revision 34755)
+++ io.c	(working copy)
@@ -2292,6 +2292,8 @@ io_readpartial(int argc, VALUE *argv, VA
         rb_eof_error();
     else
         return ret;
+
+    return Qnil; /* not reached */
 }
 
 /*
@@ -2353,6 +2355,8 @@ io_read_nonblock(int argc, VALUE *argv, 
         rb_eof_error();
     else
         return ret;
+
+    return Qnil; /* not reached */
 }
 
 /*
Index: pack.c
===================================================================
--- pack.c	(revision 34755)
+++ pack.c	(working copy)
@@ -2193,6 +2193,8 @@ rb_uv_to_utf8(char buf[6], unsigned long
 	return 6;
     }
     rb_raise(rb_eRangeError, "pack(U): value out of range");
+
+    return 0; /* not reached */
 }
 
 static const unsigned long utf8_limits[] = {
Index: proc.c
===================================================================
--- proc.c	(revision 34755)
+++ proc.c	(working copy)
@@ -1665,6 +1665,8 @@ rb_method_entry_arity(const rb_method_en
       }
     }
     rb_bug("rb_method_entry_arity: invalid method entry type (%d)", def->type);
+
+    return 0; /* not reached */
 }
 
 /*
Index: vm_method.c
===================================================================
--- vm_method.c	(revision 34755)
+++ vm_method.c	(working copy)
@@ -64,6 +64,8 @@ VALUE
 rb_f_notimplement(int argc, VALUE *argv, VALUE obj)
 {
     rb_notimplement();
+
+    return Qnil; /* not reached */
 }
 
 static void
Index: struct.c
===================================================================
--- struct.c	(revision 34755)
+++ struct.c	(working copy)
@@ -681,6 +681,8 @@ rb_struct_aset_id(VALUE s, ID id, VALUE 
 	}
     }
     rb_name_error(id, "no member '%s' in struct", rb_id2name(id));
+
+    return Qnil; /* not reached */
 }
 
 /*
Index: class.c
===================================================================
--- class.c	(revision 34755)
+++ class.c	(working copy)
@@ -1661,6 +1661,8 @@ rb_scan_args(int argc, const VALUE *argv
     else
 	rb_raise(rb_eArgError, "wrong number of arguments (%d for %d%s)",
 		 argc, n_mand, f_var ? "+" : "");
+
+    return 0; /* not reached */
 }
 
 /*!
Index: process.c
===================================================================
--- process.c	(revision 34755)
+++ process.c	(working copy)
@@ -3791,6 +3791,8 @@ rlimit_resource_type(VALUE rtype)
         return r;
 
     rb_raise(rb_eArgError, "invalid resource name: %s", name);
+
+    return 0; /* not reached */
 }
 
 static rlim_t
@@ -3829,6 +3831,8 @@ rlimit_resource_value(VALUE rval)
     if (strcmp(name, "SAVED_CUR") == 0) return RLIM_SAVED_CUR;
 #endif
     rb_raise(rb_eArgError, "invalid resource value: %s", name);
+
+    return (rlim_t)0; /* not reached */
 }
 #endif
 
@@ -5493,6 +5497,8 @@ p_uid_switch(VALUE obj)
 	errno = EPERM;
 	rb_sys_fail(0);
     }
+
+    return Qnil; /* not reached */
 }
 #else
 static VALUE
@@ -5603,6 +5609,8 @@ p_gid_switch(VALUE obj)
 	errno = EPERM;
 	rb_sys_fail(0);
     }
+
+    return Qnil; /* not reached */
 }
 #else
 static VALUE
Index: ext/digest/digest.c
===================================================================
--- ext/digest/digest.c	(revision 34755)
+++ ext/digest/digest.c	(working copy)
@@ -154,6 +154,8 @@ static VALUE
 rb_digest_instance_update(VALUE self, VALUE str)
 {
     rb_digest_instance_method_unimpl(self, "update");
+
+    return Qnil; /* not reached */
 }
 
 /*
@@ -172,6 +174,8 @@ static VALUE
 rb_digest_instance_finish(VALUE self)
 {
     rb_digest_instance_method_unimpl(self, "finish");
+
+    return Qnil; /* not reached */
 }
 
 /*
@@ -186,6 +190,8 @@ static VALUE
 rb_digest_instance_reset(VALUE self)
 {
     rb_digest_instance_method_unimpl(self, "reset");
+
+    return Qnil; /* not reached */
 }
 
 /*
@@ -409,6 +415,8 @@ static VALUE
 rb_digest_instance_block_length(VALUE self)
 {
     rb_digest_instance_method_unimpl(self, "block_length");
+
+    return Qnil; /* not reached */
 }
 
 /*
Index: ext/bigdecimal/bigdecimal.c
===================================================================
--- ext/bigdecimal/bigdecimal.c	(revision 34755)
+++ ext/bigdecimal/bigdecimal.c	(working copy)
@@ -971,6 +971,8 @@ BigDecimalCmp(VALUE self, VALUE r,char o
     }
 
     rb_bug("Undefined operation in BigDecimalCmp()");
+
+    return Qnil; /* not reached */
 }
 
 /* Returns True if the value is zero. */
Index: ext/dl/handle.c
===================================================================
--- ext/dl/handle.c	(revision 34755)
+++ ext/dl/handle.c	(working copy)
@@ -78,6 +78,8 @@ rb_dlhandle_close(VALUE self)
 	return INT2NUM(ret);
     }
     rb_raise(rb_eDLError, "dlclose() called too many times");
+
+    return Qnil; /* not reached */
 }
 
 VALUE
Index: ext/tk/tcltklib.c
===================================================================
--- ext/tk/tcltklib.c	(revision 34755)
+++ ext/tk/tcltklib.c	(working copy)
@@ -1407,6 +1407,8 @@ pending_exception_check0()
     } else {
         return 0;
     }
+
+    return 0; /* not reached */
 }
 
 static int
@@ -1448,6 +1450,8 @@ pending_exception_check1(thr_crit_bup, p
     } else {
         return 0;
     }
+
+    return 0; /* not reached */
 }
 
 
@@ -7781,6 +7785,8 @@ ip_cancel_eval_core(interp, msg, flag)
 #if TCL_MAJOR_VERSION < 8 || (TCL_MAJOR_VERSION == 8 && TCL_MINOR_VERSION < 6)
     rb_raise(rb_eNotImpError,
 	     "cancel_eval is supported Tcl/Tk8.6 or later.");
+
+    return 0; /* not reached */
 #else
     Tcl_Obj *msg_obj;
 
@@ -10014,6 +10020,8 @@ lib_get_reltype_name(self)
     default:
       rb_raise(rb_eRuntimeError, "tcltklib has invalid release type number");
     }
+
+    return Qnil; /* not reached */
 }
 
 
@@ -10117,6 +10125,8 @@ create_dummy_encoding_for_tk_core(interp
       return Qnil;
     }
   }
+
+  return Qnil; /* not reached */
 #else
     return name;
 #endif
Index: ext/tk/tkutil/tkutil.c
===================================================================
--- ext/tk/tkutil/tkutil.c	(revision 34755)
+++ ext/tk/tkutil/tkutil.c	(working copy)
@@ -803,6 +803,8 @@ tk_hash_kv(argc, argv, self)
         }
         rb_raise(rb_eArgError, "Hash is expected for 1st argument");
     }
+
+    return Qnil; /* not reached */
 }
 
 static VALUE
Index: ext/fiddle/conversions.c
===================================================================
--- ext/fiddle/conversions.c	(revision 34755)
+++ ext/fiddle/conversions.c	(working copy)
@@ -134,6 +134,8 @@ generic_to_value(VALUE rettype, fiddle_g
       default:
 	rb_raise(rb_eRuntimeError, "unknown type %d", type);
     }
+
+    return Qnil; /* not reached */
 }
 
 /* vim: set noet sw=4 sts=4 */
Index: ext/socket/raddrinfo.c
===================================================================
--- ext/socket/raddrinfo.c	(revision 34755)
+++ ext/socket/raddrinfo.c	(working copy)
@@ -2144,6 +2144,8 @@ rsock_io_socket_addrinfo(VALUE io, struc
       default:
         rb_raise(rb_eTypeError, "neither IO nor file descriptor");
     }
+
+    return Qnil; /* not reached */
 }
 
 /*
Index: ext/socket/socket.c
===================================================================
--- ext/socket/socket.c	(revision 34755)
+++ ext/socket/socket.c	(working copy)
@@ -1334,6 +1334,8 @@ sock_s_getnameinfo(int argc, VALUE *argv
   error_exit_name:
     if (res) freeaddrinfo(res);
     rsock_raise_socket_error("getnameinfo", error);
+
+  return Qnil; /* not reached */
 }
 
 /*
Index: ext/ripper/eventids2.c
===================================================================
--- ext/ripper/eventids2.c	(revision 34755)
+++ ext/ripper/eventids2.c	(working copy)
@@ -274,4 +274,6 @@ ripper_token2eventid(int tok)
         return ripper_id_CHAR;
     }
     rb_raise(rb_eRuntimeError, "[Ripper FATAL] unknown token %d", tok);
+
+    return (ID)NULL; /* not reached */
 }
Index: cont.c
===================================================================
--- cont.c	(revision 34755)
+++ cont.c	(working copy)
@@ -1110,6 +1110,8 @@ return_fiber(void)
 	fib->prev = Qnil;
 	return prev;
     }
+
+    return Qnil; /* not reached */
 }
 
 VALUE rb_fiber_transfer(VALUE fib, int argc, VALUE *argv);
Index: dmydln.c
===================================================================
--- dmydln.c	(revision 34755)
+++ dmydln.c	(working copy)
@@ -4,4 +4,6 @@ void*
 dln_load(const char *file)
 {
     rb_loaderror("this executable file can't load extension libraries");
+
+    return NULL;
 }
Index: vm_insnhelper.c
===================================================================
--- vm_insnhelper.c	(revision 34755)
+++ vm_insnhelper.c	(working copy)
@@ -1464,6 +1464,8 @@ vm_search_normal_superclass(VALUE klass,
     else {
 	rb_bug("vm_search_normal_superclass: should not be reach here");
     }
+
+    return Qnil; /* not reached */
 }
 
 static void
Index: bignum.c
===================================================================
--- bignum.c	(revision 34755)
+++ bignum.c	(working copy)
@@ -2992,7 +2992,8 @@ big_fdiv(VALUE x, VALUE y)
 	goto bignum;
     }
     rb_bug("big_fdiv");
-    /* NOTREACHED */
+
+    return Qnil; /* NOTREACHED */
 }
 
 /*
Index: marshal.c
===================================================================
--- marshal.c	(revision 34755)
+++ marshal.c	(working copy)
@@ -1143,6 +1143,8 @@ r_symlink(struct load_arg *arg)
 	return (ID)id;
     }
     rb_raise(rb_eArgError, "bad symbol");
+
+    return (ID)NULL; /* not reached */
 }
 
 static ID
@@ -1190,6 +1192,8 @@ r_symbol(struct load_arg *arg)
 	rb_raise(rb_eArgError, "dump format error for symbol(0x%x)", type);
 	break;
     }
+
+    return (ID)NULL; /* not reached */
 }
 
 static VALUE