* @stream: a #GOutputStream.
* @buffer: (array length=count) (element-type guint8): the buffer containing the data to write.
* @count: the number of bytes to write
- * @bytes_written: (out): location to store the number of bytes that was
+ * @bytes_written: (out) (optional): location to store the number of bytes that was
* written to the stream
* @cancellable: (nullable): optional #GCancellable object, %NULL to ignore.
* @error: location to store the error occurring, or %NULL to ignore
/**
* g_output_stream_printf:
* @stream: a #GOutputStream.
- * @bytes_written: (out): location to store the number of bytes that was
+ * @bytes_written: (out) (optional): location to store the number of bytes that was
* written to the stream
* @cancellable: (nullable): optional #GCancellable object, %NULL to ignore.
* @error: location to store the error occurring, or %NULL to ignore
/**
* g_output_stream_vprintf:
* @stream: a #GOutputStream.
- * @bytes_written: (out): location to store the number of bytes that was
+ * @bytes_written: (out) (optional): location to store the number of bytes that was
* written to the stream
* @cancellable: (nullable): optional #GCancellable object, %NULL to ignore.
* @error: location to store the error occurring, or %NULL to ignore
* g_output_stream_write_all_finish:
* @stream: a #GOutputStream
* @result: a #GAsyncResult
- * @bytes_written: (out): location to store the number of bytes that was written to the stream
+ * @bytes_written: (out) (optional): location to store the number of bytes that was written to the stream
* @error: a #GError location to store the error occurring, or %NULL to ignore.
*
* Finishes an asynchronous stream write operation started with