From 99b79d1f4c659fe061674142cbe09387446f8722 Mon Sep 17 00:00:00 2001
From: Nicolas Williams <nico@twosigma.com>
Date: Thu, 10 Nov 2016 12:40:35 -0600
Subject: [PATCH] Check for mig(1), not just libdispatch

---
 cf/dispatch.m4 | 29 ++++++++++++++++-------------
 1 file changed, 16 insertions(+), 13 deletions(-)

diff --git a/cf/dispatch.m4 b/cf/dispatch.m4
index 68b39fd48..76c5f47ee 100644
--- a/cf/dispatch.m4
+++ b/cf/dispatch.m4
@@ -1,20 +1,23 @@
 
 AC_DEFUN([rk_LIBDISPATCH],[
 
-AC_CHECK_HEADERS([dispatch/dispatch.h])
+AC_CHECK_PROGS(GCD_MIG, mig, no)
 
-AC_FIND_FUNC_NO_LIBS(dispatch_async_f, dispatch,
-[#ifdef HAVE_DISPATCH_DISPATCH_H
-#include <dispatch/dispatch.h>
-#endif],[0,0,0])
+if test "$GCD_MIG" != no; then
+  AC_CHECK_HEADERS([dispatch/dispatch.h])
+  AC_FIND_FUNC_NO_LIBS(dispatch_async_f, dispatch,
+  [#ifdef HAVE_DISPATCH_DISPATCH_H
+  #include <dispatch/dispatch.h>
+  #endif],[0,0,0])
+
+  if test "$ac_cv_func_dispatch_async_f" = yes -a "$GCD_MIG" != no; then
+      AC_DEFINE([HAVE_GCD], 1, [Define if os support gcd.])
+      libdispatch=yes
+  else
+      libdispatch=no
+  fi
 
-if test "$ac_cv_func_dispatch_async_f" = yes ; then
-    AC_DEFINE([HAVE_GCD], 1, [Define if os support gcd.])
-    libdispatch=yes
-else
-    libdispatch=no
 fi
+AM_CONDITIONAL(have_gcd, test "$libdispatch" = yes -a "$GCD_MIG" != no)
 
-AM_CONDITIONAL(have_gcd, test "$libdispatch" = yes)
-
-])
\ No newline at end of file
+])