Add JE_RUNNABLE() and use it for os_unfair_lock_*() test.
This resolves #494.
diff --git a/configure.ac b/configure.ac
index 053e5d7..2413673 100644
--- a/configure.ac
+++ b/configure.ac
@@ -43,6 +43,17 @@
[$4=no])])
])
+dnl JE_RUNNABLE(label, hcode, mcode, rvar)
+AC_DEFUN([JE_RUNNABLE],
+[
+AC_CACHE_CHECK([whether $1 is runnable],
+ [$4],
+ [AC_RUN_IFELSE([AC_LANG_PROGRAM([$2],
+ [$3])],
+ [$4=yes],
+ [$4=no])])
+])
+
dnl ============================================================================
CONFIG=`echo ${ac_configure_args} | sed -e 's#'"'"'\([^ ]*\)'"'"'#\1#g'`
@@ -1649,7 +1660,11 @@
dnl ============================================================================
dnl Check for os_unfair_lock operations as provided on Darwin.
-JE_COMPILABLE([Darwin os_unfair_lock_*()], [
+dnl Run the test program rather than merely compiling so that dyld lazy symbol
+dnl binding doesn't result in a false positive if building with a version of
+dnl XCode (>7) that supports the API on a system that is too old to actually
+dnl implement it (<10.12).
+JE_RUNNABLE([Darwin os_unfair_lock_*()], [
#include <os/lock.h>
], [
os_unfair_lock lock = OS_UNFAIR_LOCK_INIT;
