sysinfo.cc: Always abort on GetNumCPUs failure

Defines a wrapper function, CheckNumCPUs, which enforces that GetNumCPUs
never returns fewer than one CPU.  There is no reasonable way to
continue if we are unable to identify the number of CPUs.

This is a followup to #1753.

Signed-off-by: Sam James <[email protected]>

src/sysinfo.cc

@@ -474,44 +474,51 @@ std::string GetSystemName() {
 #endif  // Catch-all POSIX block.
 }
 
+int CheckNumCPUs(const int num_cpus) {
+  if (num_cpus < 1) {
+    PrintErrorAndDie(
+        "Unable to extract number of CPUs.  If your platform uses "
+        "/proc/cpuinfo, custom support may need to be added.");
+  }
+  return num_cpus;
+}
+
 int GetNumCPUs() {
 #ifdef BENCHMARK_HAS_SYSCTL
   int num_cpu = -1;
-  if (GetSysctl("hw.ncpu", &num_cpu)) return num_cpu;
-  fprintf(stderr, "Err: %s\n", strerror(errno));
-  std::exit(EXIT_FAILURE);
+  if (GetSysctl("hw.ncpu", &num_cpu)) return CheckNumCPUs(num_cpu);
+  PrintErrorAndDie("Err: ", sterror(errno));
 #elif defined(BENCHMARK_OS_WINDOWS)
   SYSTEM_INFO sysinfo;
   // Use memset as opposed to = {} to avoid GCC missing initializer false
   // positives.
   std::memset(&sysinfo, 0, sizeof(SYSTEM_INFO));
   GetSystemInfo(&sysinfo);
-  return sysinfo.dwNumberOfProcessors;  // number of logical
-                                        // processors in the current
-                                        // group
+  return CheckNumCPUs(sysinfo.dwNumberOfProcessors);  // number of logical
+                                                      // processors in the
+                                                      // current group
 #elif defined(BENCHMARK_OS_SOLARIS)
   // Returns -1 in case of a failure.
   long num_cpu = sysconf(_SC_NPROCESSORS_ONLN);
   if (num_cpu < 0) {
-    fprintf(stderr, "sysconf(_SC_NPROCESSORS_ONLN) failed with error: %s\n",
-            strerror(errno));
+    PrintErrorAndDie("sysconf(_SC_NPROCESSORS_ONLN) failed with error: ",
+                     strerror(errno));
   }
-  return (int)num_cpu;
+  return CheckNumCPUs(static_cast<int>(num_cpu));
 #elif defined(BENCHMARK_OS_QNX)
-  return static_cast<int>(_syspage_ptr->num_cpu);
+  return CheckNumCPUs(static_cast<int>(_syspage_ptr->num_cpu));
 #elif defined(BENCHMARK_OS_QURT)
   qurt_sysenv_max_hthreads_t hardware_threads;
   if (qurt_sysenv_get_max_hw_threads(&hardware_threads) != QURT_EOK) {
     hardware_threads.max_hthreads = 1;
   }
-  return hardware_threads.max_hthreads;
+  return CheckNumCPUs(hardware_threads.max_hthreads);
 #else
   int num_cpus = 0;
   int max_id = -1;
   std::ifstream f("/proc/cpuinfo");
   if (!f.is_open()) {
-    std::cerr << "failed to open /proc/cpuinfo\n";
-    return -1;
+    PrintErrorAndDie("Failed to open /proc/cpuinfo");
   }
 #if defined(__alpha__)
   const std::string Key = "cpus detected";
@@ -540,12 +547,10 @@ int GetNumCPUs() {
     }
   }
   if (f.bad()) {
-    std::cerr << "Failure reading /proc/cpuinfo\n";
-    return -1;
+    PrintErrorAndDie("Failure reading /proc/cpuinfo");
   }
   if (!f.eof()) {
-    std::cerr << "Failed to read to end of /proc/cpuinfo\n";
-    return -1;
+    PrintErrorAndDie("Failed to read to end of /proc/cpuinfo");
   }
   f.close();
 
@@ -554,7 +559,7 @@ int GetNumCPUs() {
             "CPU ID assignments in /proc/cpuinfo seem messed up."
             " This is usually caused by a bad BIOS.\n");
   }
-  return num_cpus;
+  return CheckNumCPUs(num_cpus);
 #endif
   BENCHMARK_UNREACHABLE();
 }