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>

diff --git a/configure.ac b/configure.ac
index 837d018e37d8d04e8e32614eca2e7da40101b9f3..19d9ea220a0fb672608236a26d3b9941091e0689 100644 (file)
--- 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])