+Implies SB-SYS:WITHOUT-INTERRUPTS for BODY, and causes any nested
+SB-SYS:WITH-INTERRUPTS to signal a warning during execution of the BODY.
+
+Should be used with great care, and not at all in multithreaded application
+code: Any locks that are ever acquired while GC is inhibited need to be always
+held with GC inhibited to prevent deadlocks: if T1 holds the lock and is
+stopped for GC while T2 is waiting for the lock inside WITHOUT-GCING the
+system will be deadlocked. Since SBCL does not currently document its internal
+locks, application code can never be certain that this invariant is
+maintained."
+ (with-unique-names (without-gcing-body)
+ `(dx-flet ((,without-gcing-body ()
+ ,@body))
+ (if *gc-inhibit*
+ (,without-gcing-body)
+ ;; We need to disable interrupts before disabling GC, so
+ ;; that signal handlers using locks don't accidentally try
+ ;; to grab them with GC inhibited.
+ (let ((*in-without-gcing* t))
+ (unwind-protect
+ (let* ((*allow-with-interrupts* nil)
+ (*interrupts-enabled* nil)
+ (*gc-inhibit* t))
+ (,without-gcing-body))
+ ;; This is not racy becuase maybe_defer_handler
+ ;; defers signals if *GC-INHIBIT* is NIL but there
+ ;; is a pending gc or stop-for-gc.
+ (when (or *interrupt-pending*
+ *gc-pending*
+ #!+sb-thread *stop-for-gc-pending*)
+ (sb!unix::receive-pending-interrupt))))))))