PollableReturn
Added in version 2.60.
- class PollableReturn
Return value for various IO operations that signal errors via the
return value and not necessarily via a Error.
This enum exists to be able to return errors to callers without having to
allocate a Error. Allocating Error can be quite expensive for
regularly happening errors like WOULD_BLOCK.
In case of FAILED a Error should be set for the
operation to give details about the error that happened.