Do we have a convention for how to comment `#else`'s and the like? (paging @charris...) I prefer the convention[1] where you always describe the sense of the thing that holds in the block that's being described, so this would be
```
#else /* not NPY_RELAXED_STRIDES_CHECKING */
#else /* ! NPY_RELAXED_STRIDES_CHECKING */
```
(and similarly on the `#endif` and on the other case below)

[1] E.g. https://www.gnu.org/prep/standards/standards.html#Comments