Fix getting the CPU frequency on OS X

src/sysinfo.cc

@@ -280,29 +280,24 @@ void InitializeSystemInfo() {
                                                     // group
 
 #elif defined BENCHMARK_OS_MACOSX
-  // returning "mach time units" per second. the current number of elapsed
-  // mach time units can be found by calling uint64 mach_absolute_time();
-  // while not as precise as actual CPU cycles, it is accurate in the face
-  // of CPU frequency scaling and multi-cpu/core machines.
-  // Our mac users have these types of machines, and accuracy
-  // (i.e. correctness) trumps precision.
-  // See cycleclock.h: CycleClock::Now(), which returns number of mach time
-  // units on Mac OS X.
-  mach_timebase_info_data_t timebase_info;
-  mach_timebase_info(&timebase_info);
-  double mach_time_units_per_nanosecond =
-      static_cast<double>(timebase_info.denom) /
-      static_cast<double>(timebase_info.numer);
-  cpuinfo_cycles_per_second = mach_time_units_per_nanosecond * 1e9;
-
-  int num_cpus = 0;
+  int32_t num_cpus = 0;
   size_t size = sizeof(num_cpus);
-  int numcpus_name[] = {CTL_HW, HW_NCPU};
-  if (::sysctl(numcpus_name, arraysize(numcpus_name), &num_cpus, &size, nullptr,
-               0) == 0 &&
-      (size == sizeof(num_cpus)))
+  if (::sysctlbyname("hw.ncpu", &num_cpus, &size, nullptr, 0) == 0 &&
+      (size == sizeof(num_cpus))) {
     cpuinfo_num_cpus = num_cpus;
-
+  } else {
+    fprintf(stderr, "%s\n", strerror(errno));
+    std::exit(EXIT_FAILURE);
+  }
+  int64_t cpu_freq = 0;
+  size = sizeof(cpu_freq);
+  if (::sysctlbyname("hw.cpufrequency", &cpu_freq, &size, nullptr, 0) == 0 &&
+      (size == sizeof(cpu_freq))) {
+    cpuinfo_cycles_per_second = cpu_freq;
+  } else {
+    fprintf(stderr, "%s\n", strerror(errno));
+    std::exit(EXIT_FAILURE);
+  }
 #else
   // Generic cycles per second counter
   cpuinfo_cycles_per_second = static_cast<double>(EstimateCyclesPerSecond());