configure.ac: enable C++14

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

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

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>
 

m4/ax_cxx_compile_stdcxx_0x.m4

-# ============================================================================
-#  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
-])

m4/ax_cxx_compile_stdcxx_14.m4

+# ============================================================================
+#  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])])

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

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
 

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)