1 files changed, 31 insertions, 0 deletions
diff --git a/third_party/glog/m4/ac_rwlock.m4 b/third_party/glog/m4/ac_rwlock.m4
new file mode 100644
index 000000000000..5065bcc1c5c2
--- /dev/null
+++ b/third_party/glog/m4/ac_rwlock.m4
@@ -0,0 +1,31 @@
+# TODO(csilvers): it would be better to actually try to link against
+# -pthreads, to make sure it defines these methods, but that may be
+# too hard, since pthread support is really tricky.
+
+# Check for support for pthread_rwlock_init() etc.
+# These aren't posix, but are widely supported.  To get them on linux,
+# you need to define _XOPEN_SOURCE first, so this check assumes your
+# application does that.
+#
+# Note: OS X (as of 6/1/06) seems to support pthread_rwlock, but
+# doesn't define PTHREAD_RWLOCK_INITIALIZER.  Therefore, we don't test
+# that particularly macro.  It's probably best if you don't use that
+# macro in your code either.
+
+AC_DEFUN([AC_RWLOCK],
+[AC_CACHE_CHECK(support for pthread_rwlock_* functions,
+ac_cv_rwlock,
+[AC_LANG_SAVE
+ AC_LANG_C
+ AC_TRY_COMPILE([#define _XOPEN_SOURCE 500
+                 #include <pthread.h>],
+		[pthread_rwlock_t l; pthread_rwlock_init(&l, NULL);
+                 pthread_rwlock_rdlock(&l); 
+                 return 0;],
+                ac_cv_rwlock=yes, ac_cv_rwlock=no)
+ AC_LANG_RESTORE
+])
+if test "$ac_cv_rwlock" = yes; then
+  AC_DEFINE(HAVE_RWLOCK,1,[define if the compiler implements pthread_rwlock_*])
+fi
+])