diff -ur /Users/dan/src/M2/M2.git/M2/BUILD/dan/builds.tmp/gallium-master/libraries/gc/tmp/gc-8.0.4/darwin_stop_world.c gc-8.0.4/darwin_stop_world.c
--- /Users/dan/src/M2/M2.git/M2/BUILD/dan/builds.tmp/gallium-master/libraries/gc/tmp/gc-8.0.4/darwin_stop_world.c	2019-03-02 02:54:41.000000000 -0600
+++ gc-8.0.4/darwin_stop_world.c	2019-11-01 11:44:11.000000000 -0500
@@ -23,6 +23,14 @@
 
 #include <sys/sysctl.h>
 #include <mach/machine.h>
+
+/* take from <dispatch/object.h> */
+#if __has_include(<sys/qos.h>)
+typedef qos_class_t dispatch_qos_class_t;
+#else
+typedef unsigned int dispatch_qos_class_t;
+#endif
+
 #include <CoreFoundation/CoreFoundation.h>
 
 /* From "Inside Mac OS X - Mach-O Runtime Architecture" published by Apple
