--- a/util-src/pposix.c	Tue Jul 31 23:38:02 2012 +0200
+++ b/util-src/pposix.c	Tue Jul 31 23:43:34 2012 +0200
@@ -674,6 +674,10 @@
 		lua_pushstring(L, strerror(errno));
 		return 2;
 	}
+#else
+#warning Only using posix_fallocate() fallback.
+#warning Linux fallocate() is strongly recommended if available: recompile with -D_GNU_SOURCE
+#warning Note that posix_fallocate() will still be used on filesystems that dont support fallocate()
 #endif
 
 	if(posix_fallocate(fileno(f), offset, len) == 0)