From 9b5724cd5808f45fd77edd6189a10f199d8f0153 Mon Sep 17 00:00:00 2001
From: Christian Brauner <christian.brauner@ubuntu.com>
Date: Wed, 22 Aug 2018 00:04:19 +0200
Subject: [PATCH] autotools: check if compiler is new enough

We line up with the Linux kernel and won't support any compiler under 4.6.
Additionally, we also require at least gnu99 so this is due anyway.

Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com>
---
 configure.ac | 16 ++++++++++++++++
 1 file changed, 16 insertions(+)

diff --git a/configure.ac b/configure.ac
index 837d018e3..19d9ea220 100644
--- a/configure.ac
+++ b/configure.ac
@@ -45,6 +45,22 @@ AC_CANONICAL_HOST
 AM_PROG_CC_C_O
 AC_GNU_SOURCE
 
+# Test if we have a new enough compiler.
+AC_COMPILE_IFELSE([AC_LANG_PROGRAM([[
+#define GCC_VERSION \
+	(__GNUC__ * 10000 + __GNUC_MINOR__ * 100 + __GNUC_PATCHLEVEL__)
+
+#define CLANG_VERSION \
+	(__clang_major__ * 10000 + __clang_minor__ * 100 + __clang_patchlevel__)
+
+#if GCC_VERSION < 40600 && CLANG_VERSION < 10000
+#error Sorry, your compiler is too old - please upgrade it
+#endif
+	]])], [valid_compiler=yes], [valid_compiler=no])
+if test "x$valid_compiler" = "xno"; then
+	AC_MSG_ERROR([Sorry, your compiler is too old - please upgrade it])
+fi
+
 # libtool
 LT_INIT
 AC_SUBST([LIBTOOL_DEPS])