return None if cpu_count() is undetermined + add mock test

3 files changed, 15 insertions, 11 deletions

diff --git a/psutil/_psutil_windows.c b/psutil/_psutil_windows.c
index 130ffd41..53c4a33c 100644
--- a/psutil/_psutil_windows.c
+++ b/psutil/_psutil_windows.c
@@ -591,7 +591,7 @@ psutil_cpu_count(PyObject *self, PyObject *args) {
                                      "GetLogicalProcessorInformation");
     if (glpi == NULL) {
         psutil_debug("failed loading GetLogicalProcessorInformation()");
-        goto return_none;
+        goto return_null_result;
     }
 
     while (1) {
@@ -608,7 +608,7 @@ psutil_cpu_count(PyObject *self, PyObject *args) {
                 }
             }
             else {
-                goto return_none;
+                goto return_null_result;
             }
         }
         else {
@@ -628,16 +628,12 @@ psutil_cpu_count(PyObject *self, PyObject *args) {
     }
 
     free(buffer);
-    if (logicalProcessorCount == 0)
-        goto return_none;
-    else
-        return Py_BuildValue("II", logicalProcessorCount, processorCoreCount);
+    return Py_BuildValue("II", logicalProcessorCount, processorCoreCount);
 
-return_none:
-    // mimic os.cpu_count()
+return_null_result:
     if (buffer != NULL)
         free(buffer);
-    Py_RETURN_NONE;
+    return Py_BuildValue("ii", 0, 0);
 }
 
 
diff --git a/psutil/_pswindows.py b/psutil/_pswindows.py
index 56546b43..078f225a 100644
--- a/psutil/_pswindows.py
+++ b/psutil/_pswindows.py
@@ -284,12 +284,12 @@ def per_cpu_times():
 
 def cpu_count_logical():
     """Return the number of logical CPUs in the system."""
-    return cext.cpu_count()[0]
+    return cext.cpu_count()[0] or None
 
 
 def cpu_count_physical():
     """Return the number of physical CPU cores in the system."""
-    return cext.cpu_count()[1]
+    return cext.cpu_count()[1] or None
 
 
 def cpu_stats():
diff --git a/psutil/tests/test_windows.py b/psutil/tests/test_windows.py
index 32c46f67..252201c5 100755
--- a/psutil/tests/test_windows.py
+++ b/psutil/tests/test_windows.py
@@ -92,6 +92,14 @@ class TestSystemAPIs(unittest.TestCase):
         psutil_value = psutil.cpu_count()
         self.assertEqual(sys_value, psutil_value)
 
+    def test_cpu_count_mocked(self):
+        # Emulate a case where the C extension is unable to determine
+        # CPU count.
+        with mock.patch('psutil._pswindows.cext.cpu_count',
+                        return_value=(0, 0)):
+            self.assertIsNone(psutil.cpu_count(logical=True))
+            self.assertIsNone(psutil.cpu_count(logical=False))
+
     def test_cpu_freq(self):
         w = wmi.WMI()
         proc = w.Win32_Processor()[0]