A memoryview that does not have a reference to its base object can point to memory that has been freed. Then a segfault error occurs when trying to access the freed memory section. You can reach the PR here.
To reproduce the case;
import io
class File(io.RawIOBase):
def readinto(self, buf):
global view
view = buf
def readable(self):
return True
f = io.BufferedReader(File())
f.read(1) # get view of buffer used by BufferedReader
del f # deallocate buffer
view = view.cast('P')
L = [None] * len(view) # create list whose array has same size
# (this will probably coincide with view)
view[0] = 0 # overwrite first item with NULL
print(L[0])