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fpm_event_select_wait() and fpm_event_poll_wait() read q->next after firing the event, but fpm_stdio_child_said() deletes its own event when a worker pipe reaches EOF, which frees q. The iterator must not touch a node a callback may have freed, so save the successor before firing, as the timer loop in fpm_event_loop() already does. With catch_workers_output enabled, the loop reads freed memory when a worker exits under select, and under poll on Linux when the worker leaves unread output in its pipe. With glibc this crashes the master.
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When a worker pipe reaches EOF, fpm_stdio_child_said() deletes its own event, freeing the queue node that fpm_event_select_wait() and fpm_event_poll_wait() then read
nextfrom. Withcatch_workers_output = yesthis happens when a worker exits under select, and under poll when it leaves unread output (on Linux an empty pipe at EOF raises only POLLHUP); with glibc the master segfaults. The loops now save the successor before firing, as the timer loop already does, and no fd callback can free that node.