BUG: Fix corner cases when value is NaN.

The case is illustrated below:
In "_safe_ceil_to_intp":
    ivalue = npy_ceil(value);   <= ivalue is NaN when value is NaN.
    if (ivalue < NPY_MIN_INTP || ivalue > NPY_MAX_INTP) {
        return -1;  <= this is never executed when ivalue is NaN.
    }

    *ret = (npy_intp)ivalue;  <= this is undefined behavior when ivalue is NaN.

2 files changed, 6 insertions, 1 deletions

diff --git a/numpy/core/src/multiarray/ctors.c b/numpy/core/src/multiarray/ctors.c
index 60f76bf5e..e1989bab8 100644
--- a/numpy/core/src/multiarray/ctors.c
+++ b/numpy/core/src/multiarray/ctors.c
@@ -2940,7 +2940,8 @@ static int _safe_ceil_to_intp(double value, npy_intp* ret)
     double ivalue;
 
     ivalue = npy_ceil(value);
-    if (ivalue < NPY_MIN_INTP || ivalue > NPY_MAX_INTP) {
+    /* condition inverted to handle NaN */
+    if (!(NPY_MIN_INTP <= ivalue && ivalue <= NPY_MAX_INTP)) {
         return -1;
     }
 
diff --git a/numpy/core/tests/test_multiarray.py b/numpy/core/tests/test_multiarray.py
index 3bddfe2ae..f55bd0e2b 100644
--- a/numpy/core/tests/test_multiarray.py
+++ b/numpy/core/tests/test_multiarray.py
@@ -7270,6 +7270,10 @@ def test_npymath_real():
                 expected = npfun(z)
                 assert_allclose(got, expected)
 
+# Test when (stop - start) / step is NaN, ValueError is raised instead
+# of returning a zero-length array.
+def test_arange_nan():
+    assert_raises(ValueError, np.arange, 0, 1, np.nan)
 
 if __name__ == "__main__":
     run_module_suite()