This API misuse is intended to produce an error value to detect certain bogus stub implementations of MADV_WIPEONFORK. We don't need to log a warning about it. Example: https://boringssl.googlesource.com/boringssl/+/ad5582985cc6b89d0e7caf0d9cc7e301de61cf66%5E%21/ Reviewed by: emaste, trasz Differential Revision: https://reviews.freebsd.org/D27017