+/* Check whether a fatal signal has occurred and, if so, call the fatal signal
+ * hooks and exit.
+ *
+ * This function is called automatically by poll_block(), but specialized
+ * programs that may not always call poll_block() on a regular basis should
+ * also call it periodically. (Therefore, any function with "block" in its
+ * name should call fatal_signal_run() each time it is called, either directly
+ * or through poll_block(), because such functions can only used by specialized
+ * programs that can afford to block outside their main loop around
+ * poll_block().)
+ */