configure.ac: enable C++14

9 files changed, 607 insertions, 152 deletions

diff --git a/NEWS b/NEWS
index 634c53f06..6a6a90018 100644
--- a/NEWS
+++ b/NEWS
@@ -53,6 +53,8 @@ ver 0.20 (not yet released)
   - proxy: add TCP keepalive option
 * update
   - apply .mpdignore matches to subdirectories
+* switch the code base to C++14
+  - GCC 4.9 or clang 3.4 (or newer) recommended
 
 ver 0.19.20 (not yet released)
 * decoder
diff --git a/configure.ac b/configure.ac
index d94cad3b1..d4ac95b20 100644
--- a/configure.ac
+++ b/configure.ac
@@ -186,14 +186,7 @@ dnl ---------------------------------------------------------------------------
 dnl Language Checks
 dnl ---------------------------------------------------------------------------
 
-AC_CXX_COMPILE_STDCXX_0X
-if test "$ax_cv_cxx_compile_cxx0x_native" != yes; then
-	if test "$ax_cv_cxx_compile_cxx0x_gxx" = yes; then
-	   	AM_CXXFLAGS="$AM_CXXFLAGS -std=gnu++0x"
-	elif test "$ax_cv_cxx_compile_cxx0x_cxx" = yes; then
-	   	AM_CXXFLAGS="$AM_CXXFLAGS -std=c++0x"
-	fi
-fi
+AX_CXX_COMPILE_STDCXX_14([noext], [mandatory])
 
 dnl ---------------------------------------------------------------------------
 dnl Header/Library Checks
diff --git a/doc/developer.xml b/doc/developer.xml
index f07c52000..f7a121323 100644
--- a/doc/developer.xml
+++ b/doc/developer.xml
@@ -41,8 +41,8 @@
       <listitem>
         <para>
           the code should be C++11 compliant, and must compile with
-          <application>GCC</application> 4.7 and
-          <application>clang</application> 3.2
+          <application>GCC</application> 4.9 and
+          <application>clang</application> 3.4
         </para>
       </listitem>
 
diff --git a/m4/ax_cxx_compile_stdcxx.m4 b/m4/ax_cxx_compile_stdcxx.m4
new file mode 100644
index 000000000..2c18e49c5
--- /dev/null
+++ b/m4/ax_cxx_compile_stdcxx.m4
@@ -0,0 +1,562 @@
+# ===========================================================================
+#   http://www.gnu.org/software/autoconf-archive/ax_cxx_compile_stdcxx.html
+# ===========================================================================
+#
+# SYNOPSIS
+#
+#   AX_CXX_COMPILE_STDCXX(VERSION, [ext|noext], [mandatory|optional])
+#
+# DESCRIPTION
+#
+#   Check for baseline language coverage in the compiler for the specified
+#   version of the C++ standard.  If necessary, add switches to CXX and
+#   CXXCPP to enable support.  VERSION may be '11' (for the C++11 standard)
+#   or '14' (for the C++14 standard).
+#
+#   The second argument, if specified, indicates whether you insist on an
+#   extended mode (e.g. -std=gnu++11) or a strict conformance mode (e.g.
+#   -std=c++11).  If neither is specified, you get whatever works, with
+#   preference for an extended mode.
+#
+#   The third argument, if specified 'mandatory' or if left unspecified,
+#   indicates that baseline support for the specified C++ standard is
+#   required and that the macro should error out if no mode with that
+#   support is found.  If specified 'optional', then configuration proceeds
+#   regardless, after defining HAVE_CXX${VERSION} if and only if a
+#   supporting mode is found.
+#
+# LICENSE
+#
+#   Copyright (c) 2008 Benjamin Kosnik <bkoz@redhat.com>
+#   Copyright (c) 2012 Zack Weinberg <zackw@panix.com>
+#   Copyright (c) 2013 Roy Stogner <roystgnr@ices.utexas.edu>
+#   Copyright (c) 2014, 2015 Google Inc.; contributed by Alexey Sokolov <sokolov@google.com>
+#   Copyright (c) 2015 Paul Norman <penorman@mac.com>
+#   Copyright (c) 2015 Moritz Klammler <moritz@klammler.eu>
+#
+#   Copying and distribution of this file, with or without modification, are
+#   permitted in any medium without royalty provided the copyright notice
+#   and this notice are preserved.  This file is offered as-is, without any
+#   warranty.
+
+#serial 4
+
+dnl  This macro is based on the code from the AX_CXX_COMPILE_STDCXX_11 macro
+dnl  (serial version number 13).
+
+AC_DEFUN([AX_CXX_COMPILE_STDCXX], [dnl
+  m4_if([$1], [11], [],
+        [$1], [14], [],
+        [$1], [17], [m4_fatal([support for C++17 not yet implemented in AX_CXX_COMPILE_STDCXX])],
+        [m4_fatal([invalid first argument `$1' to AX_CXX_COMPILE_STDCXX])])dnl
+  m4_if([$2], [], [],
+        [$2], [ext], [],
+        [$2], [noext], [],
+        [m4_fatal([invalid second argument `$2' to AX_CXX_COMPILE_STDCXX])])dnl
+  m4_if([$3], [], [ax_cxx_compile_cxx$1_required=true],
+        [$3], [mandatory], [ax_cxx_compile_cxx$1_required=true],
+        [$3], [optional], [ax_cxx_compile_cxx$1_required=false],
+        [m4_fatal([invalid third argument `$3' to AX_CXX_COMPILE_STDCXX])])
+  AC_LANG_PUSH([C++])dnl
+  ac_success=no
+  AC_CACHE_CHECK(whether $CXX supports C++$1 features by default,
+  ax_cv_cxx_compile_cxx$1,
+  [AC_COMPILE_IFELSE([AC_LANG_SOURCE([_AX_CXX_COMPILE_STDCXX_testbody_$1])],
+    [ax_cv_cxx_compile_cxx$1=yes],
+    [ax_cv_cxx_compile_cxx$1=no])])
+  if test x$ax_cv_cxx_compile_cxx$1 = xyes; then
+    ac_success=yes
+  fi
+
+  m4_if([$2], [noext], [], [dnl
+  if test x$ac_success = xno; then
+    for switch in -std=gnu++$1 -std=gnu++0x; do
+      cachevar=AS_TR_SH([ax_cv_cxx_compile_cxx$1_$switch])
+      AC_CACHE_CHECK(whether $CXX supports C++$1 features with $switch,
+                     $cachevar,
+        [ac_save_CXX="$CXX"
+         CXX="$CXX $switch"
+         AC_COMPILE_IFELSE([AC_LANG_SOURCE([_AX_CXX_COMPILE_STDCXX_testbody_$1])],
+          [eval $cachevar=yes],
+          [eval $cachevar=no])
+         CXX="$ac_save_CXX"])
+      if eval test x\$$cachevar = xyes; then
+        CXX="$CXX $switch"
+        if test -n "$CXXCPP" ; then
+          CXXCPP="$CXXCPP $switch"
+        fi
+        ac_success=yes
+        break
+      fi
+    done
+  fi])
+
+  m4_if([$2], [ext], [], [dnl
+  if test x$ac_success = xno; then
+    dnl HP's aCC needs +std=c++11 according to:
+    dnl http://h21007.www2.hp.com/portal/download/files/unprot/aCxx/PDF_Release_Notes/769149-001.pdf
+    dnl Cray's crayCC needs "-h std=c++11"
+    for switch in -std=c++$1 -std=c++0x +std=c++$1 "-h std=c++$1"; do
+      cachevar=AS_TR_SH([ax_cv_cxx_compile_cxx$1_$switch])
+      AC_CACHE_CHECK(whether $CXX supports C++$1 features with $switch,
+                     $cachevar,
+        [ac_save_CXX="$CXX"
+         CXX="$CXX $switch"
+         AC_COMPILE_IFELSE([AC_LANG_SOURCE([_AX_CXX_COMPILE_STDCXX_testbody_$1])],
+          [eval $cachevar=yes],
+          [eval $cachevar=no])
+         CXX="$ac_save_CXX"])
+      if eval test x\$$cachevar = xyes; then
+        CXX="$CXX $switch"
+        if test -n "$CXXCPP" ; then
+          CXXCPP="$CXXCPP $switch"
+        fi
+        ac_success=yes
+        break
+      fi
+    done
+  fi])
+  AC_LANG_POP([C++])
+  if test x$ax_cxx_compile_cxx$1_required = xtrue; then
+    if test x$ac_success = xno; then
+      AC_MSG_ERROR([*** A compiler with support for C++$1 language features is required.])
+    fi
+  fi
+  if test x$ac_success = xno; then
+    HAVE_CXX$1=0
+    AC_MSG_NOTICE([No compiler with C++$1 support was found])
+  else
+    HAVE_CXX$1=1
+    AC_DEFINE(HAVE_CXX$1,1,
+              [define if the compiler supports basic C++$1 syntax])
+  fi
+  AC_SUBST(HAVE_CXX$1)
+])
+
+
+dnl  Test body for checking C++11 support
+
+m4_define([_AX_CXX_COMPILE_STDCXX_testbody_11],
+  _AX_CXX_COMPILE_STDCXX_testbody_new_in_11
+)
+
+
+dnl  Test body for checking C++14 support
+
+m4_define([_AX_CXX_COMPILE_STDCXX_testbody_14],
+  _AX_CXX_COMPILE_STDCXX_testbody_new_in_11
+  _AX_CXX_COMPILE_STDCXX_testbody_new_in_14
+)
+
+
+dnl  Tests for new features in C++11
+
+m4_define([_AX_CXX_COMPILE_STDCXX_testbody_new_in_11], [[
+
+// If the compiler admits that it is not ready for C++11, why torture it?
+// Hopefully, this will speed up the test.
+
+#ifndef __cplusplus
+
+#error "This is not a C++ compiler"
+
+#elif __cplusplus < 201103L
+
+#error "This is not a C++11 compiler"
+
+#else
+
+namespace cxx11
+{
+
+  namespace test_static_assert
+  {
+
+    template <typename T>
+    struct check
+    {
+      static_assert(sizeof(int) <= sizeof(T), "not big enough");
+    };
+
+  }
+
+  namespace test_final_override
+  {
+
+    struct Base
+    {
+      virtual void f() {}
+    };
+
+    struct Derived : public Base
+    {
+      virtual void f() override {}
+    };
+
+  }
+
+  namespace test_double_right_angle_brackets
+  {
+
+    template < typename T >
+    struct check {};
+
+    typedef check<void> single_type;
+    typedef check<check<void>> double_type;
+    typedef check<check<check<void>>> triple_type;
+    typedef check<check<check<check<void>>>> quadruple_type;
+
+  }
+
+  namespace test_decltype
+  {
+
+    int
+    f()
+    {
+      int a = 1;
+      decltype(a) b = 2;
+      return a + b;
+    }
+
+  }
+
+  namespace test_type_deduction
+  {
+
+    template < typename T1, typename T2 >
+    struct is_same
+    {
+      static const bool value = false;
+    };
+
+    template < typename T >
+    struct is_same<T, T>
+    {
+      static const bool value = true;
+    };
+
+    template < typename T1, typename T2 >
+    auto
+    add(T1 a1, T2 a2) -> decltype(a1 + a2)
+    {
+      return a1 + a2;
+    }
+
+    int
+    test(const int c, volatile int v)
+    {
+      static_assert(is_same<int, decltype(0)>::value == true, "");
+      static_assert(is_same<int, decltype(c)>::value == false, "");
+      static_assert(is_same<int, decltype(v)>::value == false, "");
+      auto ac = c;
+      auto av = v;
+      auto sumi = ac + av + 'x';
+      auto sumf = ac + av + 1.0;
+      static_assert(is_same<int, decltype(ac)>::value == true, "");
+      static_assert(is_same<int, decltype(av)>::value == true, "");
+      static_assert(is_same<int, decltype(sumi)>::value == true, "");
+      static_assert(is_same<int, decltype(sumf)>::value == false, "");
+      static_assert(is_same<int, decltype(add(c, v))>::value == true, "");
+      return (sumf > 0.0) ? sumi : add(c, v);
+    }
+
+  }
+
+  namespace test_noexcept
+  {
+
+    int f() { return 0; }
+    int g() noexcept { return 0; }
+
+    static_assert(noexcept(f()) == false, "");
+    static_assert(noexcept(g()) == true, "");
+
+  }
+
+  namespace test_constexpr
+  {
+
+    template < typename CharT >
+    unsigned long constexpr
+    strlen_c_r(const CharT *const s, const unsigned long acc) noexcept
+    {
+      return *s ? strlen_c_r(s + 1, acc + 1) : acc;
+    }
+
+    template < typename CharT >
+    unsigned long constexpr
+    strlen_c(const CharT *const s) noexcept
+    {
+      return strlen_c_r(s, 0UL);
+    }
+
+    static_assert(strlen_c("") == 0UL, "");
+    static_assert(strlen_c("1") == 1UL, "");
+    static_assert(strlen_c("example") == 7UL, "");
+    static_assert(strlen_c("another\0example") == 7UL, "");
+
+  }
+
+  namespace test_rvalue_references
+  {
+
+    template < int N >
+    struct answer
+    {
+      static constexpr int value = N;
+    };
+
+    answer<1> f(int&)       { return answer<1>(); }
+    answer<2> f(const int&) { return answer<2>(); }
+    answer<3> f(int&&)      { return answer<3>(); }
+
+    void
+    test()
+    {
+      int i = 0;
+      const int c = 0;
+      static_assert(decltype(f(i))::value == 1, "");
+      static_assert(decltype(f(c))::value == 2, "");
+      static_assert(decltype(f(0))::value == 3, "");
+    }
+
+  }
+
+  namespace test_uniform_initialization
+  {
+
+    struct test
+    {
+      static const int zero {};
+      static const int one {1};
+    };
+
+    static_assert(test::zero == 0, "");
+    static_assert(test::one == 1, "");
+
+  }
+
+  namespace test_lambdas
+  {
+
+    void
+    test1()
+    {
+      auto lambda1 = [](){};
+      auto lambda2 = lambda1;
+      lambda1();
+      lambda2();
+    }
+
+    int
+    test2()
+    {
+      auto a = [](int i, int j){ return i + j; }(1, 2);
+      auto b = []() -> int { return '0'; }();
+      auto c = [=](){ return a + b; }();
+      auto d = [&](){ return c; }();
+      auto e = [a, &b](int x) mutable {
+        const auto identity = [](int y){ return y; };
+        for (auto i = 0; i < a; ++i)
+          a += b--;
+        return x + identity(a + b);
+      }(0);
+      return a + b + c + d + e;
+    }
+
+    int
+    test3()
+    {
+      const auto nullary = [](){ return 0; };
+      const auto unary = [](int x){ return x; };
+      using nullary_t = decltype(nullary);
+      using unary_t = decltype(unary);
+      const auto higher1st = [](nullary_t f){ return f(); };
+      const auto higher2nd = [unary](nullary_t f1){
+        return [unary, f1](unary_t f2){ return f2(unary(f1())); };
+      };
+      return higher1st(nullary) + higher2nd(nullary)(unary);
+    }
+
+  }
+
+  namespace test_variadic_templates
+  {
+
+    template <int...>
+    struct sum;
+
+    template <int N0, int... N1toN>
+    struct sum<N0, N1toN...>
+    {
+      static constexpr auto value = N0 + sum<N1toN...>::value;
+    };
+
+    template <>
+    struct sum<>
+    {
+      static constexpr auto value = 0;
+    };
+
+    static_assert(sum<>::value == 0, "");
+    static_assert(sum<1>::value == 1, "");
+    static_assert(sum<23>::value == 23, "");
+    static_assert(sum<1, 2>::value == 3, "");
+    static_assert(sum<5, 5, 11>::value == 21, "");
+    static_assert(sum<2, 3, 5, 7, 11, 13>::value == 41, "");
+
+  }
+
+  // http://stackoverflow.com/questions/13728184/template-aliases-and-sfinae
+  // Clang 3.1 fails with headers of libstd++ 4.8.3 when using std::function
+  // because of this.
+  namespace test_template_alias_sfinae
+  {
+
+    struct foo {};
+
+    template<typename T>
+    using member = typename T::member_type;
+
+    template<typename T>
+    void func(...) {}
+
+    template<typename T>
+    void func(member<T>*) {}
+
+    void test();
+
+    void test() { func<foo>(0); }
+
+  }
+
+}  // namespace cxx11
+
+#endif  // __cplusplus >= 201103L
+
+]])
+
+
+dnl  Tests for new features in C++14
+
+m4_define([_AX_CXX_COMPILE_STDCXX_testbody_new_in_14], [[
+
+// If the compiler admits that it is not ready for C++14, why torture it?
+// Hopefully, this will speed up the test.
+
+#ifndef __cplusplus
+
+#error "This is not a C++ compiler"
+
+#elif __cplusplus < 201402L
+
+#error "This is not a C++14 compiler"
+
+#else
+
+namespace cxx14
+{
+
+  namespace test_polymorphic_lambdas
+  {
+
+    int
+    test()
+    {
+      const auto lambda = [](auto&&... args){
+        const auto istiny = [](auto x){
+          return (sizeof(x) == 1UL) ? 1 : 0;
+        };
+        const int aretiny[] = { istiny(args)... };
+        return aretiny[0];
+      };
+      return lambda(1, 1L, 1.0f, '1');
+    }
+
+  }
+
+  namespace test_binary_literals
+  {
+
+    constexpr auto ivii = 0b0000000000101010;
+    static_assert(ivii == 42, "wrong value");
+
+  }
+
+  namespace test_generalized_constexpr
+  {
+
+    template < typename CharT >
+    constexpr unsigned long
+    strlen_c(const CharT *const s) noexcept
+    {
+      auto length = 0UL;
+      for (auto p = s; *p; ++p)
+        ++length;
+      return length;
+    }
+
+    static_assert(strlen_c("") == 0UL, "");
+    static_assert(strlen_c("x") == 1UL, "");
+    static_assert(strlen_c("test") == 4UL, "");
+    static_assert(strlen_c("another\0test") == 7UL, "");
+
+  }
+
+  namespace test_lambda_init_capture
+  {
+
+    int
+    test()
+    {
+      auto x = 0;
+      const auto lambda1 = [a = x](int b){ return a + b; };
+      const auto lambda2 = [a = lambda1(x)](){ return a; };
+      return lambda2();
+    }
+
+  }
+
+  namespace test_digit_seperators
+  {
+
+    constexpr auto ten_million = 100'000'000;
+    static_assert(ten_million == 100000000, "");
+
+  }
+
+  namespace test_return_type_deduction
+  {
+
+    auto f(int& x) { return x; }
+    decltype(auto) g(int& x) { return x; }
+
+    template < typename T1, typename T2 >
+    struct is_same
+    {
+      static constexpr auto value = false;
+    };
+
+    template < typename T >
+    struct is_same<T, T>
+    {
+      static constexpr auto value = true;
+    };
+
+    int
+    test()
+    {
+      auto x = 0;
+      static_assert(is_same<int, decltype(f(x))>::value, "");
+      static_assert(is_same<int&, decltype(g(x))>::value, "");
+      return x;
+    }
+
+  }
+
+}  // namespace cxx14
+
+#endif  // __cplusplus >= 201402L
+
+]])
diff --git a/m4/ax_cxx_compile_stdcxx_0x.m4 b/m4/ax_cxx_compile_stdcxx_0x.m4
deleted file mode 100644
index d11b7918a..000000000
--- a/m4/ax_cxx_compile_stdcxx_0x.m4
+++ /dev/null
@@ -1,107 +0,0 @@
-# ============================================================================
-#  http://www.gnu.org/software/autoconf-archive/ax_cxx_compile_stdcxx_0x.html
-# ============================================================================
-#
-# SYNOPSIS
-#
-#   AX_CXX_COMPILE_STDCXX_0X
-#
-# DESCRIPTION
-#
-#   Check for baseline language coverage in the compiler for the C++0x
-#   standard.
-#
-# LICENSE
-#
-#   Copyright (c) 2008 Benjamin Kosnik <bkoz@redhat.com>
-#
-#   Copying and distribution of this file, with or without modification, are
-#   permitted in any medium without royalty provided the copyright notice
-#   and this notice are preserved. This file is offered as-is, without any
-#   warranty.
-
-#serial 8
-
-AU_ALIAS([AC_CXX_COMPILE_STDCXX_0X], [AX_CXX_COMPILE_STDCXX_0X])
-AC_DEFUN([AX_CXX_COMPILE_STDCXX_0X], [
-  AC_CACHE_CHECK(if g++ supports C++0x features without additional flags,
-  ax_cv_cxx_compile_cxx0x_native,
-  [AC_LANG_SAVE
-  AC_LANG_CPLUSPLUS
-  AC_TRY_COMPILE([
-  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);],,
-  ax_cv_cxx_compile_cxx0x_native=yes, ax_cv_cxx_compile_cxx0x_native=no)
-  AC_LANG_RESTORE
-  ])
-
-  AC_CACHE_CHECK(if g++ supports C++0x features with -std=c++0x,
-  ax_cv_cxx_compile_cxx0x_cxx,
-  [AC_LANG_SAVE
-  AC_LANG_CPLUSPLUS
-  ac_save_CXXFLAGS="$CXXFLAGS"
-  CXXFLAGS="$CXXFLAGS -std=c++0x"
-  AC_TRY_COMPILE([
-  template <typename T>
-    struct check
-    {
-      static_assert(sizeof(int) <= sizeof(T), "not big enough");
-    };
-
-    typedef check<check<bool>> right_angle_brackets;
-
-    int a;
-    decltype(a) b;
-
-    typedef check<int> check_type;
-    check_type c;
-    check_type&& cr = static_cast<check_type&&>(c);],,
-  ax_cv_cxx_compile_cxx0x_cxx=yes, ax_cv_cxx_compile_cxx0x_cxx=no)
-  CXXFLAGS="$ac_save_CXXFLAGS"
-  AC_LANG_RESTORE
-  ])
-
-  AC_CACHE_CHECK(if g++ supports C++0x features with -std=gnu++0x,
-  ax_cv_cxx_compile_cxx0x_gxx,
-  [AC_LANG_SAVE
-  AC_LANG_CPLUSPLUS
-  ac_save_CXXFLAGS="$CXXFLAGS"
-  CXXFLAGS="$CXXFLAGS -std=gnu++0x"
-  AC_TRY_COMPILE([
-  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);],,
-  ax_cv_cxx_compile_cxx0x_gxx=yes, ax_cv_cxx_compile_cxx0x_gxx=no)
-  CXXFLAGS="$ac_save_CXXFLAGS"
-  AC_LANG_RESTORE
-  ])
-
-  if test "$ax_cv_cxx_compile_cxx0x_native" = yes ||
-     test "$ax_cv_cxx_compile_cxx0x_cxx" = yes ||
-     test "$ax_cv_cxx_compile_cxx0x_gxx" = yes; then
-    AC_DEFINE(HAVE_STDCXX_0X,,[Define if g++ supports C++0x features. ])
-  fi
-])
diff --git a/m4/ax_cxx_compile_stdcxx_14.m4 b/m4/ax_cxx_compile_stdcxx_14.m4
new file mode 100644
index 000000000..51123f2d5
--- /dev/null
+++ b/m4/ax_cxx_compile_stdcxx_14.m4
@@ -0,0 +1,34 @@
+# ============================================================================
+#  http://www.gnu.org/software/autoconf-archive/ax_cxx_compile_stdcxx_14.html
+# ============================================================================
+#
+# SYNOPSIS
+#
+#   AX_CXX_COMPILE_STDCXX_14([ext|noext], [mandatory|optional])
+#
+# DESCRIPTION
+#
+#   Check for baseline language coverage in the compiler for the C++14
+#   standard; if necessary, add switches to CXX and CXXCPP to enable
+#   support.
+#
+#   This macro is a convenience alias for calling the AX_CXX_COMPILE_STDCXX
+#   macro with the version set to C++14.  The two optional arguments are
+#   forwarded literally as the second and third argument respectively.
+#   Please see the documentation for the AX_CXX_COMPILE_STDCXX macro for
+#   more information.  If you want to use this macro, you also need to
+#   download the ax_cxx_compile_stdcxx.m4 file.
+#
+# LICENSE
+#
+#   Copyright (c) 2015 Moritz Klammler <moritz@klammler.eu>
+#
+#   Copying and distribution of this file, with or without modification, are
+#   permitted in any medium without royalty provided the copyright notice
+#   and this notice are preserved. This file is offered as-is, without any
+#   warranty.
+
+#serial 4
+
+AX_REQUIRE_DEFINED([AX_CXX_COMPILE_STDCXX])
+AC_DEFUN([AX_CXX_COMPILE_STDCXX_14], [AX_CXX_COMPILE_STDCXX([14], [$1], [$2])])
diff --git a/src/Chrono.hxx b/src/Chrono.hxx
index 3bb1cc469..96e871d8b 100644
--- a/src/Chrono.hxx
+++ b/src/Chrono.hxx
@@ -20,19 +20,10 @@
 #ifndef MPD_CHRONO_HXX
 #define MPD_CHRONO_HXX
 
-#include "Compiler.h"
-
 #include <chrono>
 #include <utility>
 #include <cstdint>
 
-#if GCC_OLDER_THAN(4,7)
-/* std::chrono::duration operators are "constexpr" since gcc 4.7 */
-#define chrono_constexpr gcc_pure
-#else
-#define chrono_constexpr constexpr
-#endif
-
 /**
  * A time stamp within a song.  Granularity is 1 millisecond and the
  * maximum value is about 49 days.
@@ -108,11 +99,11 @@ public:
 		return count() > 0;
 	}
 
-	chrono_constexpr SongTime operator+(const SongTime &other) const {
+	constexpr SongTime operator+(const SongTime &other) const {
 		return SongTime(*(const Base *)this + (const Base &)other);
 	}
 
-	chrono_constexpr SongTime operator-(const SongTime &other) const {
+	constexpr SongTime operator-(const SongTime &other) const {
 		return SongTime(*(const Base *)this - (const Base &)other);
 	}
 };
@@ -212,15 +203,13 @@ public:
 		return count() < 0;
 	}
 
-	chrono_constexpr SignedSongTime operator+(const SignedSongTime &other) const {
+	constexpr SignedSongTime operator+(const SignedSongTime &other) const {
 		return SignedSongTime(*(const Base *)this + (const Base &)other);
 	}
 
-	chrono_constexpr SignedSongTime operator-(const SignedSongTime &other) const {
+	constexpr SignedSongTime operator-(const SignedSongTime &other) const {
 		return SignedSongTime(*(const Base *)this - (const Base &)other);
 	}
 };
 
-#undef chrono_constexpr
-
 #endif
diff --git a/src/Compiler.h b/src/Compiler.h
index 957aca551..af82cc107 100644
--- a/src/Compiler.h
+++ b/src/Compiler.h
@@ -62,8 +62,8 @@
 #    error Sorry, your clang version is too old.  You need at least version 3.1.
 #  endif
 #elif defined(__GNUC__)
-#  if GCC_OLDER_THAN(4,7)
-#    error Sorry, your gcc version is too old.  You need at least version 4.6.
+#  if GCC_OLDER_THAN(4,9)
+#    error Sorry, your gcc version is too old.  You need at least version 4.9.
 #  endif
 #else
 #  warning Untested compiler.  Use at your own risk!
@@ -97,8 +97,6 @@
 #define gcc_likely(x) __builtin_expect (!!(x), 1)
 #define gcc_unlikely(x) __builtin_expect (!!(x), 0)
 
-#define gcc_aligned(n) __attribute__((aligned(n)))
-
 #define gcc_visibility_hidden __attribute__((visibility("hidden")))
 #define gcc_visibility_default __attribute__((visibility("default")))
 
@@ -126,8 +124,6 @@
 #define gcc_likely(x) (x)
 #define gcc_unlikely(x) (x)
 
-#define gcc_aligned(n)
-
 #define gcc_visibility_hidden
 #define gcc_visibility_default
 
@@ -168,17 +164,7 @@
 
 #if defined(__cplusplus)
 
-/* support for C++11 "override" was added in gcc 4.7 */
-#if GCC_OLDER_THAN(4,7)
-#define override
-#define final
-#endif
-
-#if CLANG_OR_GCC_VERSION(4,8)
 #define gcc_alignas(T, fallback) alignas(T)
-#else
-#define gcc_alignas(T, fallback) gcc_aligned(fallback)
-#endif
 
 #endif
 
diff --git a/src/util/Manual.hxx b/src/util/Manual.hxx
index 6ba932bdd..115f2e7bd 100644
--- a/src/util/Manual.hxx
+++ b/src/util/Manual.hxx
@@ -35,10 +35,6 @@
 #include <new>
 #include <utility>
 
-#if GCC_OLDER_THAN(4,8)
-#include <type_traits>
-#endif
-
 #include <assert.h>
 
 #if CLANG_OR_GCC_VERSION(4,7)