SSL_set_verify_result() sets verify_result of the object ssl to be the result of the verification of the X509 certificate presented by the peer, if any.
SSL_set_verify_result() overrides the verification result. It only changes the verification result of the ssl object. It does not become part of the established session, so if the session is to be reused later, the original value will reappear.
The valid codes for verify_result are documented in verify(1).