configure.ac: require C++11 compiler

We'll add some C++11 code soon.

Makefile.am

@@ -1316,7 +1316,6 @@ test_test_queue_priority_SOURCES = \
 test_test_queue_priority_LDADD = \
 	$(GLIB_LIBS)
 
-if HAVE_CXX
 noinst_PROGRAMS += src/dsd2pcm/dsd2pcm
 
 src_dsd2pcm_dsd2pcm_SOURCES = \
@@ -1324,7 +1323,6 @@ src_dsd2pcm_dsd2pcm_SOURCES = \
 	src/dsd2pcm/noiseshape.c src/dsd2pcm/noiseshape.h \
 	src/dsd2pcm/main.cpp
 src_dsd2pcm_dsd2pcm_LDADD = libutil.a
-endif
 
 endif
 

configure.ac

@@ -21,24 +21,9 @@ dnl Programs
 dnl ---------------------------------------------------------------------------
 AC_PROG_CC_C99
 AC_PROG_CXX
+AC_CXX_COMPILE_STDCXX_0X
 AC_PROG_RANLIB
 
-HAVE_CXX=yes
-if test x$CXX = xg++; then
-	# CXX=g++ probably means that autoconf hasn't found any C++
-	# compiler; to be sure, we check again
-	AC_PATH_PROG(CXX, $CXX, no)
-	if test x$CXX = xno; then
-		# no, we don't have C++ - the following hack is
-		# required because automake insists on using $(CXX)
-		# for linking the MPD binary
-		AC_MSG_NOTICE([Disabling C++ support])
-		CXX="$CC"
-		HAVE_CXX=no
-	fi
-fi
-AM_CONDITIONAL(HAVE_CXX, test x$HAVE_CXX = xyes)
-
 AC_PROG_INSTALL
 AC_PROG_MAKE_SET
 PKG_PROG_PKG_CONFIG
@@ -899,9 +884,6 @@ fi
 AM_CONDITIONAL(ENABLE_MIKMOD_DECODER, test x$enable_mikmod = xyes)
 
 dnl -------------------------------- libmodplug -------------------------------
-found_modplug=$HAVE_CXX
-MPD_AUTO_PRE(modplug, [modplug decoder plugin], [No C++ compiler found])
-
 MPD_AUTO_PKG(modplug, MODPLUG, [libmodplug],
 	[modplug decoder plugin], [libmodplug not found])
 
@@ -1010,9 +992,6 @@ fi
 AM_CONDITIONAL(ENABLE_VORBIS_DECODER, test x$enable_vorbis = xyes || test x$enable_tremor = xyes)
 
 dnl --------------------------------- sidplay ---------------------------------
-found_sidplay=$HAVE_CXX
-MPD_AUTO_PRE(sidplay, [sidplay decoder plugin], [No C++ compiler found])
-
 if test x$enable_sidplay != xno; then
 	# we're not using pkg-config here
 	# because libsidplay2's .pc file requires libtool

m4/ax_cxx_compile_stdcxx_0x.m4

@@ -0,0 +1,107 @@
+# ============================================================================
+#  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 7
+
+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
+])