Unreachable should call V8_Fatal on release builds instead of silently ignoring the error.

src/base/logging.h

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef V8_BASE_LOGGING_H_
 #define V8_BASE_LOGGING_H_
 
 #include <cstring>
 #include <sstream>
 #include <string>
@@ skipping 11 matching lines @@
   V8_Fatal(__FILE__, __LINE__, "%s", (msg))
 #define UNIMPLEMENTED()                         \
   V8_Fatal(__FILE__, __LINE__, "unimplemented code")
 #define UNREACHABLE()                           \
   V8_Fatal(__FILE__, __LINE__, "unreachable code")
 #else
 #define FATAL(msg)                              \
   V8_Fatal("", 0, "%s", (msg))
 #define UNIMPLEMENTED()                         \
   V8_Fatal("", 0, "unimplemented code")
-#define UNREACHABLE() ((void) 0)
+#define UNREACHABLE() V8_Fatal("", 0, "unreachable code")
 #endif
 
 
 namespace v8 {
 namespace base {
 
 // CHECK dies with a fatal error if condition is not true.  It is *not*
 // controlled by DEBUG, so the check will be executed regardless of
 // compilation mode.
 //
@@ skipping 125 matching lines @@
 #define DCHECK_GT(v1, v2)      ((void) 0)
 #define DCHECK_GE(v1, v2)      ((void) 0)
 #define DCHECK_LT(v1, v2)      ((void) 0)
 #define DCHECK_LE(v1, v2)      ((void) 0)
 #define DCHECK_NULL(val)       ((void) 0)
 #define DCHECK_NOT_NULL(val)   ((void) 0)
 #define DCHECK_IMPLIES(v1, v2) ((void) 0)
 #endif
 
 #endif  // V8_BASE_LOGGING_H_