2 files changed, 63 insertions, 32 deletions

diff --git a/numpy/core/src/multiarray/arraytypes.c.src b/numpy/core/src/multiarray/arraytypes.c.src
index 5a1e2f4d5..58c234745 100644
--- a/numpy/core/src/multiarray/arraytypes.c.src
+++ b/numpy/core/src/multiarray/arraytypes.c.src
@@ -3099,28 +3099,33 @@ static int
 
 static int
 OBJECT_argmax(PyObject **ip, npy_intp n, npy_intp *max_ind,
-        PyArrayObject *NPY_UNUSED(aip))
+              PyArrayObject *NPY_UNUSED(aip))
 {
     npy_intp i;
-    PyObject *mp = ip[0];
 
     *max_ind = 0;
-    i = 1;
-    while (i < n && mp == NULL) {
-        mp = ip[i];
-        i++;
-    }
-    for (; i < n; i++) {
-        ip++;
-#if defined(NPY_PY3K)
-        if (*ip != NULL && PyObject_RichCompareBool(*ip, mp, Py_GT) == 1) {
-#else
-        if (*ip != NULL && PyObject_Compare(*ip, mp) > 0) {
-#endif
-            mp = *ip;
-            *max_ind = i;
+    /* Skip over all leading NULL entries */
+    for (i = 0; i < n && ip[i] == NULL; ++i);
+    if (i < n) {
+        /* Found first non-NULL entry */
+        PyObject *mp = ip[i];
+        *max_ind = i;
+        for (i = i + 1; i < n; ++i) {
+            PyObject *val = ip[i];
+            if (val != NULL) {
+                int greater_than = PyObject_RichCompareBool(val, mp, Py_GT);
+
+                if (greater_than < 0) {
+                    return 0;
+                }
+                if (greater_than) {
+                    mp = val;
+                    *max_ind = i;
+                }
+            }
         }
     }
+
     return 0;
 }
 
@@ -3158,28 +3163,33 @@ static int
 
 static int
 OBJECT_argmin(PyObject **ip, npy_intp n, npy_intp *min_ind,
-        PyArrayObject *NPY_UNUSED(aip))
+              PyArrayObject *NPY_UNUSED(aip))
 {
     npy_intp i;
-    PyObject *mp = ip[0];
 
     *min_ind = 0;
-    i = 1;
-    while (i < n && mp == NULL) {
-        mp = ip[i];
-        i++;
-    }
-    for (; i < n; i++) {
-        ip++;
-#if defined(NPY_PY3K)
-        if (*ip != NULL && PyObject_RichCompareBool(mp, *ip, Py_GT) == 1) {
-#else
-        if (*ip != NULL && PyObject_Compare(mp, *ip) > 0) {
-#endif
-            mp = *ip;
-            *min_ind = i;
+    /* Skip over all leading NULL entries */
+    for (i = 0; i < n && ip[i] == NULL; ++i);
+    if (i < n) {
+        /* Found first non-NULL entry */
+        PyObject *mp = ip[i];
+        *min_ind = i;
+        for (i = i + 1; i < n ; ++i) {
+            PyObject *val = ip[i];
+            if (val != NULL) {
+                int less_than = PyObject_RichCompareBool(val, mp, Py_LT);
+
+                if (less_than < 0) {
+                    return 0;
+                }
+                if (less_than) {
+                    mp = val;
+                    *min_ind = i;
+                }
+            }
         }
     }
+
     return 0;
 }
 
diff --git a/numpy/core/tests/test_multiarray.py b/numpy/core/tests/test_multiarray.py
index 3cab3cf3e..d7e919269 100644
--- a/numpy/core/tests/test_multiarray.py
+++ b/numpy/core/tests/test_multiarray.py
@@ -8,6 +8,7 @@ import warnings
 import operator
 import io
 import itertools
+import ctypes
 if sys.version_info[0] >= 3:
     import builtins
 else:
@@ -2802,6 +2803,16 @@ class TestArgmax(TestCase):
         assert_equal(a.argmax(out=out1, axis=0), np.argmax(a, out=out2, axis=0))
         assert_equal(out1, out2)
 
+    def test_object_argmax_with_NULLs(self):
+        # See gh-6032
+        a = np.empty(4, dtype='O')
+        ctypes.memset(a.ctypes.data, 0, a.nbytes)
+        assert_equal(a.argmax(), 0)
+        a[3] = 10
+        assert_equal(a.argmax(), 3)
+        a[1] = 30
+        assert_equal(a.argmax(), 1)
+
 
 class TestArgmin(TestCase):
 
@@ -2940,6 +2951,16 @@ class TestArgmin(TestCase):
         assert_equal(a.argmin(out=out1, axis=0), np.argmin(a, out=out2, axis=0))
         assert_equal(out1, out2)
 
+    def test_object_argmin_with_NULLs(self):
+        # See gh-6032
+        a = np.empty(4, dtype='O')
+        ctypes.memset(a.ctypes.data, 0, a.nbytes)
+        assert_equal(a.argmin(), 0)
+        a[3] = 30
+        assert_equal(a.argmin(), 3)
+        a[1] = 10
+        assert_equal(a.argmin(), 1)
+
 
 class TestMinMax(TestCase):