Add __pure2 dummy macro
diff --git a/include/bsd/cdefs.h b/include/bsd/cdefs.h
index 8736e8c..d6884ad 100644
--- a/include/bsd/cdefs.h
+++ b/include/bsd/cdefs.h
@@ -37,6 +37,10 @@
# define __dead2
#endif
+#ifndef __pure2
+# define __pure2
+#endif
+
/* Linux headers define a struct with a member names __unused.
* Disable for now. */
#if 0