From d806ef795948c87e614cb2a4cfb80ec96a07d256 Mon Sep 17 00:00:00 2001
From: Michael Orlitzky <michael@orlitzky.com>
Date: Mon, 26 Feb 2018 14:56:00 -0500
Subject: [PATCH] configure.ac: add checks for openat() and O_NOFOLLOW.

---
 configure.ac | 11 ++++++++++-
 1 file changed, 10 insertions(+), 1 deletion(-)

diff --git a/configure.ac b/configure.ac
index dd028ff..130b10c 100644
--- a/configure.ac
+++ b/configure.ac
@@ -21,6 +21,15 @@ AC_TYPE_MODE_T
 AC_CHECK_HEADERS([ fcntl.h ftw.h getopt.h libgen.h limits.h sys/acl.h ])
 AC_CHECK_HEADERS([ sys/libacl.h sys/types.h unistd.h ])
 
-LT_INIT
+# We need openat() with O_NOFOLLOW from POSIX-2008. Without them, we
+# can't operate securely; I would rather refuse to be built.
+AC_CHECK_FUNC(openat,
+              [],
+	      AC_MSG_ERROR(missing required openat function))
+AC_CHECK_DECLS([O_NOFOLLOW],
+               [],
+	       [AC_MSG_ERROR(missing required O_NOFOLLOW flag in fcntl.h)],
+	       [[#include <fcntl.h>]])
 
+LT_INIT
 AC_OUTPUT
-- 
2.43.2