CLOCK_REALTIME is 0 on Linux, use -1 for invalid clock id.

src/platform/time.cc

 // Copyright 2013 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 277 matching lines @@
   // cleanup the tools/gyp/v8.gyp file.
   struct timeval tv;
   int result = gettimeofday(&tv, NULL);
   ASSERT_EQ(0, result);
   USE(result);
   return FromTimeval(tv);
 #elif defined(CLOCK_REALTIME_COARSE)
   struct timespec ts;
   // Use CLOCK_REALTIME_COARSE if it's available and has a precision of 1ms
   // or higher.  It's serviced from the vDSO with no system call overhead.
-  static clock_t clock_id = static_cast<clock_t>(0);
-  if (!clock_id) {
+  static clock_t clock_id = static_cast<clock_t>(-1);
+  STATIC_ASSERT(CLOCK_REALTIME != static_cast<clock_t>(-1));
+  STATIC_ASSERT(CLOCK_REALTIME_COARSE != static_cast<clock_t>(-1));
+  if (clock_id == static_cast<clock_t>(-1)) {
     if (clock_getres(CLOCK_REALTIME_COARSE, &ts) == 0
         && ts.tv_nsec <= kNanosecondsPerMillisecond)
       clock_id = CLOCK_REALTIME_COARSE;
     else
       clock_id = CLOCK_REALTIME;
   }
   int result = clock_gettime(clock_id, &ts);
   ASSERT_EQ(0, result);
   USE(result);
   return FromTimespec(ts);
@@ skipping 294 matching lines @@
   struct timeval tv;
   int result = gettimeofday(&tv, NULL);
   ASSERT_EQ(0, result);
   USE(result);
   ticks = (tv.tv_sec * Time::kMicrosecondsPerSecond + tv.tv_usec);
 #elif V8_OS_POSIX
   struct timespec ts;
 #if defined(CLOCK_MONOTONIC_COARSE)
   // Use CLOCK_MONOTONIC_COARSE if it's available and has a precision of 1ms
   // or higher.  It's serviced from the vDSO with no system call overhead.
-  static clock_t clock_id = static_cast<clock_t>(0);
-  if (!clock_id) {
+  static clock_t clock_id = static_cast<clock_t>(-1);
+  STATIC_ASSERT(CLOCK_MONOTONIC != static_cast<clock_t>(-1));
+  STATIC_ASSERT(CLOCK_MONOTONIC_COARSE != static_cast<clock_t>(-1));
+  if (clock_id == static_cast<clock_t>(-1)) {
     if (clock_getres(CLOCK_MONOTONIC_COARSE, &ts) == 0
         && ts.tv_nsec <= Time::kNanosecondsPerMillisecond)
       clock_id = CLOCK_MONOTONIC_COARSE;
     else
       clock_id = CLOCK_MONOTONIC;
   }
 #else
   static const clock_t clock_id = CLOCK_MONOTONIC;
 #endif  // defined(CLOCK_MONOTONIC_COARSE)
   int result = clock_gettime(clock_id, &ts);
   ASSERT_EQ(0, result);
   USE(result);
   ticks = (ts.tv_sec * Time::kMicrosecondsPerSecond +
            ts.tv_nsec / Time::kNanosecondsPerMicrosecond);
 #endif  // V8_OS_MACOSX
   // Make sure we never return 0 here.
   return TimeTicks(ticks + 1);
 }
 
 
 // static
 bool TimeTicks::IsHighResolutionClockWorking() {
   return true;
 }
 
 #endif  // V8_OS_WIN
 
 } }  // namespace v8::internal