buffer: only define _XOPEN_SOURCE ifndef

diff --git a/src/include/buffer.h b/src/include/buffer.h
index af6a9f4034b98eb3e42d80894c8260f9416e77e8..ec1ffbc8237712e57b52a8f747861db090906a26 100644 (file)
--- a/src/include/buffer.h
+++ b/src/include/buffer.h
@@ -15,7 +15,10 @@
 #ifndef __BUFFER_H
 #define __BUFFER_H
 
-#define _XOPEN_SOURCE 600
+#ifndef _XOPEN_SOURCE
+# define _XOPEN_SOURCE 600
+#endif
+
 #include <stdlib.h>
 #ifdef DARWIN