Index: lib/Fuzzer/FuzzerUtil.cpp
===================================================================
--- lib/Fuzzer/FuzzerUtil.cpp
+++ lib/Fuzzer/FuzzerUtil.cpp
@@ -273,7 +273,15 @@
   struct rusage usage;
   if (getrusage(RUSAGE_SELF, &usage))
     return 0;
+#ifdef __linux__
+  // ru_maxrss is in KiB
   return usage.ru_maxrss >> 10;
+#elif __APPLE__
+  // ru_maxrss is in bytes
+  return usage.ru_maxrss >> 20;
+#else
+#error "GetPeakRSSMb() is not implemented for your platform"
+#endif
 }
 
 }  // namespace fuzzer