-extern bool sptps_send_record(sptps_t *s, uint8_t type, const char *data, uint16_t len);
-extern bool sptps_receive_data(sptps_t *s, const char *data, size_t len);
-extern bool sptps_force_kex(sptps_t *s);
-extern bool sptps_verify_datagram(sptps_t *s, const char *data, size_t len);
+extern bool sptps_send_record(sptps_t *s, uint8_t type, const void *data, uint16_t len);
+extern bool sptps_receive_data(sptps_t *s, const void *data, size_t len) __attribute__((__warn_unused_result__));
+extern bool sptps_force_kex(sptps_t *s) __attribute__((__warn_unused_result__));
+extern bool sptps_verify_datagram(sptps_t *s, const void *data, size_t len) __attribute__((__warn_unused_result__));