+dnl Test whether system calls are restartable by default on the
+dnl current system. If they are not, we put a loop around every system
+dnl call to check for EINTR (see SCM_SYSCALL) and do not attempt to
+dnl change from the default behaviour. On the other hand, if signals
+dnl are restartable then the loop is not installed and when libguile
+dnl initialises it also resets the behaviour of each signal to cause a
+dnl restart (in case a different runtime had a different default
+dnl behaviour for some reason: e.g., different versions of linux seem
+dnl to behave differently.)
+