ecccdh_serialized_pub_key_size
ATTRIBUTE_WARN_UNUSED_RET int ecccdh_serialized_pub_key_size(const ec_params *params, u8 *size);
ret = ecccdh_serialized_pub_key_size(¶ms, &serialized_pub_key_len); EG(ret, err);
ret = ecccdh_serialized_pub_key_size(¶ms, &serialized_pub_key_size);