According to "man 2 setitimer", the same error should happen on Linux even without zend_max_execution_timer: https://github.com/php/php-src/blob/2079da0158bc91fff4edd85ac66c89b40c4faf3a/Zend/zend_execute_API.c#L1566
A C error will also occur if the value is superior to 999,999,999. We should at least prevent the C error in such cases. I proposed a patch normalizing these values to 0: https://github.com/php/php-src/pull/13942 It's still better than the current situation, and can still be considered as "undefined" until the RFC is voted.
