In this code
https://github.com/numpy/numpy-user-dtypes/blob/2134a7d2a15946536d2f1d5c33ad8896d5bea2d8/quaddtype/numpy_quaddtype/src/casts.cpp#L34-L43
given_descrs[1] is dereferenced in line 34 (given_descrs[1]->backend), so it is assumed that given_descrs[1] is not NULL. In line 40, however, there is a check for given_descrs[1] == NULL. So either the check in line 40 always fails, or there is a bug in line 34.
In this code
https://github.com/numpy/numpy-user-dtypes/blob/2134a7d2a15946536d2f1d5c33ad8896d5bea2d8/quaddtype/numpy_quaddtype/src/casts.cpp#L34-L43
given_descrs[1]is dereferenced in line 34 (given_descrs[1]->backend), so it is assumed thatgiven_descrs[1]is not NULL. In line 40, however, there is a check forgiven_descrs[1] == NULL. So either the check in line 40 always fails, or there is a bug in line 34.