BUG: segfault on to_json serializing a 0d-ndarray, #9576

Author: gpoulin

doc/source/whatsnew/v0.17.0.txt

@@ -823,3 +823,4 @@ Bug Fixes
 - Bug in ``TimedeltaIndex`` formatter causing error while trying to save ``DataFrame`` with ``TimedeltaIndex`` using ``to_csv`` (:issue:`10833`)
 - Bug in ``DataFrame.where`` when handling Series slicing (:issue:`10218`, :issue:`9558`)
 - Bug where ``pd.read_gbq`` throws ``ValueError`` when Bigquery returns zero rows (:issue:`10273`)
+- Bug in ``to_json`` which was causing segmentation fault when serializing 0-rank ndarray (:issue:`9576`)

pandas/io/tests/test_json/test_ujson.py

@@ -1035,6 +1035,12 @@ def testArrays(self):
         outp = ujson.decode(ujson.encode(arr), numpy=True, dtype=np.float32)
         assert_array_almost_equal_nulp(arr, outp)
 
+    def testOdArray(self):
+        def will_raise():
+            ujson.encode(np.array(1))
+
+        self.assertRaises(TypeError, will_raise)
+
     def testArrayNumpyExcept(self):
 
         input = ujson.dumps([42, {}, 'a'])

pandas/src/ujson/python/objToJSON.c

@@ -1863,7 +1863,7 @@ void Object_beginTypeContext (JSOBJ _obj, JSONTypeContext *tc)
   }
   tc->prv = pc;
 
-  if (PyIter_Check(obj) || PyArray_Check(obj))
+  if (PyIter_Check(obj) || (PyArray_Check(obj) && !PyArray_CheckScalar(obj) ))
   {
     PRINTMARK();
     goto ISITERABLE;
@@ -2065,6 +2065,23 @@ void Object_beginTypeContext (JSOBJ _obj, JSONTypeContext *tc)
     pc->PyTypeToJSON = NpyFloatToDOUBLE; tc->type = JT_DOUBLE;
     return;
   }
+  else
+  if (PyArray_Check(obj) && PyArray_CheckScalar(obj)) {
+    #if PY_MAJOR_VERSION >= 3
+      PyErr_Format(
+        PyExc_TypeError,
+        "%R (0d array) is not JSON serializable at the moment",
+        obj
+      );
+    #else
+      PyErr_Format(
+        PyExc_TypeError,
+        "%s (0d array) is not JSON serializable at the moment",
+        PyString_AsString(PyObject_Repr(obj))
+      );
+    #endif
+    return;
+  }
 
 ISITERABLE: