stream_select() can emit a notice if pcntl_signal handler is set up by a caller

[TysonAndre]

Observed: Sabre emits a notice.
Desired: Prevent that notice, or add a configurable way for applications using sabre\event to suppress that notice

Context: This was seen in an application calling pcntl_signal() to listen for signals, then calling pcntl_fork() to create child processes (it would get signalled from within the sabre event loop)

reactphp/reactphp#296 mentions a similar issue.
See the note in https://secure.php.net/manual/en/function.stream-select.php#refsect1-function.stream-select-returnvalues

This happens in 5.0.3, probably also in master: https://github.com/sabre-io/event/blob/5.0.3/lib/Loop/Loop.php#L305

The approach taken by reactphp looks like it was to call set_error_handler before the stream operation (e.g. stream_select()), and call restore_error_handler immediately after (and check if the error was caused by pcntl in that handler)

/path/to/vendor/sabre/event/lib/Loop/Loop.php:305 [2] stream_select(): unable to select [4]: Interrupted system call (max_fd=0)

#0  my_custom_error_handler()
#1  stream_select() called at [/path/to/vendor/sabre/event/lib/Loop/Loop.php:305]
#2  Sabre\Event\Loop\Loop->runStreams() called at [/path/to/vendor/sabre/event/lib/Loop/Loop.php:233]
#3  Sabre\Event\Loop\Loop->tick() called at [/path/to/vendor/sabre/event/lib/Loop/Loop.php:194]
#4  Sabre\Event\Loop\Loop->run() called at [/path/to/vendor/sabre/event/lib/Loop/functions.php:122]
#5  Sabre\Event\Loop\run() called at ...

I can work around this by changing my_custom_error_handler

[staabm]

Thx for reporting.

Do you have some simplified steps to reproduce?
At best a failling unit test?