restartSysCalls is not defined

[gmponos]

On this line https://github.com/Seldaek/monolog/blob/master/src/Monolog/SignalHandler.php#L96 the restartSyscalls is never defined.. I could not understand what the intention was in order to fix it 😞

[Seldaek]

Pretty sure it's a typo and should be $this->signalRestartSyscalls as that one exists and is unused.

[Seldaek]

Ping @RGustBardon though - also this should be applied on 1.x AFAIK

[RGustBardon]

@gmponos: Thank you for reporting the bug! As @Seldaek suggested, it should be $this->signalRestartHandlers.

I could not understand what the intention was in order to fix it

Thank you for attempting to come up with a fix! The idea is as follows:

When registering a signal handler, the user can require calling the signal handler previously registered for this signal after the logging of the signal is done. This is what the $callPrevious parameter of the registerSignalHandler method is responsible for. Previous signal handlers are stored in the previousSignalHandler property.

Another parameter of the registerSignalHandler method ($restartSyscalls) controls whether system calls should be restarted upon a signal (cf. usleep in SignalHandlerTest). These preferences are stored in the signalRestartSyscalls property.

Before PHP 7.1, it was not possible to get the current signal handler. Since PHP 7.1, pcntl_signal_get_handler returns either SIG_DFL (the default system handler for a given signal), SIG_IGN (ignore the signal), or a function (previously registered using pcntl_signal).

If the user wishes to call the previous signal handler after the logging takes place and pcntl_signal_get_handler returns a function, this can be done in a straightforward matter: a call to the previous handler will suffice. This is what happens at the very end of handleSignal. However, in cases the previous signal handler is unknown, handleSignal attempts to call the default signal handler (SIG_DFL) once it is done logging.

Right before making such an attempt, the current signal handler is still the one used for logging. For this reason, the signal handler is temporarily substituted with the default one (the first call to the pcntl_signal function at the end of handleSignal), the process sends the signal to itself (posix_kill), it dispatches the newly installed signal handler (pcntl_signal_dispatch), and finally restores the Monolog signal handler (the second call to the pcntl_signal function).

The current units tests have not been able to identify the problem as they never call registerSignalHandler with both $callPrevious and $restartSyscalls set to true.

@Seldaek: Thank you for bringing the bug to my attention! I have created two pull requests with the same fix (#1252 for the master branch and #1253 for the 1.x branch).

[Seldaek]

Great, thanks for the fixes :)