Add a platform-independent max uword value.

runtime/platform/globals.h

 // Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 #ifndef PLATFORM_GLOBALS_H_
 #define PLATFORM_GLOBALS_H_
 
 // __STDC_FORMAT_MACROS has to be defined to enable platform independent printf.
 #ifndef __STDC_FORMAT_MACROS
 #define __STDC_FORMAT_MACROS
@@ skipping 133 matching lines @@
 
 // Types for native machine words. Guaranteed to be able to hold pointers and
 // integers.
 typedef intptr_t word;
 typedef uintptr_t uword;
 
 // Byte sizes.
 const int kWordSize = sizeof(word);
 #ifdef ARCH_IS_32_BIT
 const int kWordSizeLog2 = 2;
+const uword kUwordMax = kMaxUint32;
 #else
 const int kWordSizeLog2 = 3;
+const uword kUwordMax = kMaxUint64;
 #endif
 
 // Bit sizes.
 const int kBitsPerByte = 8;
 const int kBitsPerByteLog2 = 3;
 const int kBitsPerWord = kWordSize * kBitsPerByte;
 
 // System-wide named constants.
 const int KB = 1024;
 const int MB = KB * KB;
@@ skipping 171 matching lines @@
 // separate lines with body in {}s).
 # define TEMP_FAILURE_RETRY(expression)                                        \
     ({ int64_t __result;                                                       \
        do {                                                                    \
          __result = (int64_t) (expression);                                    \
        } while (__result == -1L && errno == EINTR);                            \
        __result; })
 #endif
 
 #endif  // PLATFORM_GLOBALS_H_