-/* Nonzero means quit immediately if Control-C is typed now,
- rather than waiting until QUIT is executed. */
+/* Nonzero means quit immediately if Control-C is typed now, rather
+ than waiting until QUIT is executed. Be careful in setting this;
+ code which executes with immediate_quit set has to be very careful
+ about being able to deal with being interrupted at any time. It is
+ almost always better to use QUIT; the only exception I can think of
+ is being able to quit out of a system call (using EINTR loses if
+ the SIGINT happens between the previous QUIT and the system call).
+ To immediately quit in the case in which a SIGINT happens between
+ the previous QUIT and setting immediate_quit (desirable anytime we
+ expect to block), call QUIT after setting immediate_quit. */