From f3874e05ccb4a7b62df76659a166aface88e3034 Mon Sep 17 00:00:00 2001
From: Alexandre Duret-Lutz <adl@lrde.epita.fr>
Date: Sun, 15 Dec 2013 22:30:23 +0100
Subject: [PATCH] * configure.ac: Turn on C++11 flags.

---
 configure.ac | 47 +++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 47 insertions(+)

diff --git a/configure.ac b/configure.ac
index e0ec68fc3..d6c26e863 100644
--- a/configure.ac
+++ b/configure.ac
@@ -71,6 +71,53 @@ AX_CHECK_COMPILE_FLAG([-Werror -fvisibility=hidden],
     [CXXFLAGS="$CXXFLAGS -fvisibility-inlines-hidden"])])
 CXXFLAGS="$CXXFLAGS -DSPOT_BUILD"
 
+# Turn on C++11 support
+AX_CHECK_COMPILE_FLAG([-std=c++11 -stdlib=libc++],
+                      [CXXFLAGS="$CXXFLAGS -std=c++11 -stdlib=libc++"
+                       stdpass=true])
+if ! "${stdpass-false}"; then
+  AX_CHECK_COMPILE_FLAG([-std=c++11],
+                        [CXXFLAGS="$CXXFLAGS -std=c++11"
+                         stdpass=true])
+fi
+if ! "${stdpass-false}"; then
+  AX_CHECK_COMPILE_FLAG([-std=c++0x],
+                        [CXXFLAGS="$CXXFLAGS -std=c++0x"
+                         stdpass=true])
+fi
+
+if ! "${stdpass-false}"; then
+  AC_ERROR([unable to turn on C++11 mode with this compiler])
+fi
+
+m4_define([_AX_CXX_COMPILE_STDCXX_11_testbody], [
+  template <typename T>
+    struct check
+    {
+      static_assert(sizeof(int) <= sizeof(T), "not big enough");
+    };
+
+    typedef check<check<bool>> right_angle_brackets;
+
+    int a;
+    decltype(a) b;
+
+    typedef check<int> check_type;
+    check_type c;
+    check_type&& cr = static_cast<check_type&&>(c);
+
+    auto d = a;
+])
+
+AC_CACHE_CHECK([whether $CXX $CXXFLAGS supports C++11 features],
+               [ax_cv_cxx_compile_cxx11],
+[AC_COMPILE_IFELSE([AC_LANG_SOURCE([_AX_CXX_COMPILE_STDCXX_11_testbody])],
+  [ax_cv_cxx_compile_cxx11=yes],
+  [ax_cv_cxx_compile_cxx11=no])])
+
+test "x$ax_cv_cxx_compile_cxx11" = xyes ||
+  AC_ERROR([unable to compile C++11 with this compiler])
+
 AC_HEADER_UNORDERED_MAP
 AC_HEADER_TR1_UNORDERED_MAP
 AC_HEADER_EXT_HASH_MAP