Cancellable.makePollfd

Creates a #GPollFD corresponding to cancellable; this can be passed to [glib.global.poll] and used to poll for cancellation. This is useful both for unix systems without a native poll and for portability to windows.

When this function returns true, you should use [gio.cancellable.Cancellable.releaseFd] to free up resources allocated for the pollfd. After a false return, do not call [gio.cancellable.Cancellable.releaseFd].

If this function returns false, either no cancellable was given or resource limits prevent this function from allocating the necessary structures for polling. (On Linux, you will likely have reached the maximum number of file descriptors.) The suggested way to handle these cases is to ignore the cancellable.

You are not supposed to read from the fd yourself, just check for readable status. Reading to unset the readable status is done with [gio.cancellable.Cancellable.reset].