Bug #79994 [Com]: pcntl_signal_get_handler() should return SIG_IGN for externally ignored signals

Edit report at https://bugs.php.net/bug.php?id=79994&edit=1 ID: 79994 Comment by: weirdan at gmail dot com Reported by: weirdan at gmail dot com Summary: pcntl_signal_get_handler() should return SIG_IGN for externally ignored signals Status: Open Type: Bug Package: PCNTL related Operating System: Linux (Debian/sid) PHP Version: 7.4.9 Block user comment: N Private report: N New Comment: > I don't see that signal can return the current handler, though, so unless there's > another function that can then this change in behavior may have to be platform-dependent. Doesn't PHP use sigaction(), rather than signal() though? Looking at zend_sigaction() signature [1] it appears it should be possible to query the installed handler by calling zend_sigaction(SIGINT, NULL, &handler). As far as I can see, initial signal handlers are populated exactly the same way (but with actual sigaction()) into the global_orig_handlers [2] and then copied to zend_signal_globals on every request [3], from where they can be accessed by zend_sigaction() [1] https://github.com/php/php-src/blob/91fbd12d5736b3cc9fc6bc2545e877dd65be1f6c/Zend/zend_signal.c#L226 [2] https://github.com/php/php-src/blob/91fbd12d5736b3cc9fc6bc2545e877dd65be1f6c/Zend/zend_signal.c#L394-L404 [3] https://github.com/php/php-src/blob/91fbd12d5736b3cc9fc6bc2545e877dd65be1f6c/Zend/zend_signal.c#L376 Previous Comments: ------------------------------------------------------------------------ [2020-08-18 21:43:13] requinix@php.net Ah, you're reporting something slightly different than I thought. That's why I like asking questions. I'm slightly rewording the summary in case I'm not the only one mistaken. Assuming that trap(1) is calling signal(7) or sigaction(7) with SIG_IGN, and given that sigaction is capable of returning the current signal handler (including whether it's ignored), then I agree that returning SIG_IGN is better than SIG_DFL. Currently, PHP is returning what PHP was told to do. No custom handler means SIG_DFL. I don't see that signal can return the current handler, though, so unless there's another function that can then this change in behavior may have to be platform-dependent. ------------------------------------------------------------------------ [2020-08-18 21:21:42] weirdan at gmail dot com It should return SIG_IGN in this case. ------------------------------------------------------------------------ [2020-08-18 21:18:18] requinix@php.net Not a bug, but I'll get to that. First, a question: what should pcntl_signal_get_handler() be returning? ------------------------------------------------------------------------ [2020-08-18 21:07:57] weirdan at gmail dot com Description: ------------ Originally discovered by John Stevenson here: https://github.com/composer/xdebug-handler/issues/109#issuecomment-675462698 When signal is set to be ignored by the process that calls php binary, pcntl_signal_get_handler() run in the context of that binary reports that same signal as using default handler (SIG_DFL). However it's clearly doesn't use default handler, as can demonstrated by the script below. If it was using default handler, you'd be able to abort the script with Ctrl-C, but you can't. PS: use Ctrl-\ to stop it. Test script: --------------- <?php var_dump( "Is default handler is used for sigint?", pcntl_signal_get_handler(SIGINT) === SIG_DFL ); while (true) { echo "."; sleep(2); } // Run it as follows (in bash/zsh): // $ trap "" SIGINT; php test.php; trap - SIGINT; Expected result: ---------------- string(38) "Is default handler is used for sigint?" bool(false) .................. Actual result: -------------- string(38) "Is default handler is used for sigint?" bool(true) .................. ------------------------------------------------------------------------ -- Edit this bug report at https://bugs.php.net/bug.php?id=79994&edit=1