+#define ENGINE_REF_COUNT_DEBUG
+
+/* If we compile with this symbol defined, then both reference counts in the
+ * ENGINE structure will be monitored with a line of output on stderr for each
+ * change. This prints the engine's pointer address (truncated to unsigned int),
+ * "struct" or "funct" to indicate the reference type, the before and after
+ * reference count, and the file:line-number pair. The "engine_ref_debug"
+ * statements must come *after* the change. */
+#ifdef ENGINE_REF_COUNT_DEBUG
+
+#define engine_ref_debug(e, isfunct, diff) \
+ fprintf(stderr, "blargle: %08x %s from %d to %d (%s:%d)\n", \
+ (unsigned int)(e), (isfunct ? "funct" : "struct"), \
+ ((isfunct) ? ((e)->funct_ref - (diff)) : ((e)->struct_ref - (diff))), \
+ ((isfunct) ? (e)->funct_ref : (e)->struct_ref), \
+ (__FILE__), (__LINE__));
+
+#else
+
+#define engine_ref_debug(e, isfunct, diff)
+
+#endif
+
+/* NB: Bitwise OR-able values for the "flags" variable in ENGINE are now exposed
+ * in engine.h. */