Elementwise equality comparison with zero-length void dtype fails on NumPy 1.21 #19305
Description
Reproducing code example:
With NumPy 1.21:
>>> import numpy as np
>>> x = np.zeros((3,), np.void)
>>> x == x
/usr/local/lib/python3.7/dist-packages/ipykernel_launcher.py:4: FutureWarning: elementwise == comparison failed and returning scalar instead; this will raise an error or perform elementwise comparison in the future.
False
I believe the error comes from these lines:
numpy/numpy/core/src/multiarray/arrayobject.c
Lines 1361 to 1375 in 1581032
On NumPy 1.20, the output is correct:
array([ True, True, True])
Or conversely, if we use a non-zero length void dtype, e.g.,
>>> x = np.array([b'foo', b'bar'], np.void)
>>> x == x
array([ True, True])