Fix 73783 : pcntl_signal() not handling SIG_IGN correctly #2246
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Bug #73783 raises an issue with signal handling when using SIG_IGN.
With PHP7.1 ZEND_SIGNALS is defaulted to on, which will for all
signals set the handler as zend_signal_handler_defer. This is
problematic for syscalls like sleep(), which will only return when the
requisite number of seconds have elapsed, or, a non-ignored signal is
raised. In this case we want to SIG_IGN SIGCHLD, however, SIG_IGN is
only stored in the SIGG(handlers) array, and the actual system level
handler is defined. This prevents proper signal ignoring when requeted.