Add std::index_sequence for C++11

Will be required for nasal::Ghost

CMakeLists.txt

@@ -135,6 +135,16 @@ include (DetectArch)
 # keep the compatability link option as the default
 option(OSG_FSTREAM_EXPORT_FIXED "Set to ON if the osgDB fstream export patch is applied" OFF)
 
+if (CMAKE_COMPILER_IS_GNUCXX OR CLANG)
+  if (CMAKE_VERSION VERSION_LESS 3.1)
+    set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -std=c++${CMAKE_CXX_STANDARD}")
+  elseif (CMAKE_VERSION VERSION_LESS 3.8)
+    # policy CMP0067 (try_compile does not honor CMAKE_CXX_STANDARD)
+    set(CMAKE_REQUIRED_FLAGS "${CMAKE_REQUIRED_FLAGS} -std=c++${CMAKE_CXX_STANDARD}")
+  endif()
+endif()
+
+
 if (MSVC)
   GET_FILENAME_COMPONENT(PARENT_DIR ${PROJECT_BINARY_DIR} PATH)
   if (CMAKE_CL_64)
@@ -382,10 +392,6 @@ if(CMAKE_COMPILER_IS_GNUCXX)
     set(WARNING_FLAGS_CXX "-Wall -fPIC")
     set(WARNING_FLAGS_C   "-Wall -fPIC")
 
-    if (CMAKE_VERSION VERSION_LESS 3.1)
-       set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -std=c++11")
-    endif()
-
     if(CMAKE_CXX_COMPILER_VERSION VERSION_LESS 4.4)
       message(WARNING "GCC 4.4 will be required soon, please upgrade")
     endif()
@@ -413,10 +419,6 @@ if (CLANG)
     # fix Boost compilation :(
     set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -stdlib=libc++")
 
-    if (CMAKE_VERSION VERSION_LESS 3.1)
-       set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -std=c++11")
-    endif()
-
     if(ENABLE_SIMD)
       if (X86 OR X86_64)
         set(CMAKE_C_FLAGS_RELEASE "-O3 -msse2 -mfpmath=sse")
@@ -489,6 +491,14 @@ set(CMAKE_C_FLAGS "${CMAKE_C_FLAGS} ${WARNING_FLAGS_C} ${MSVC_FLAGS}")
 set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} ${WARNING_FLAGS_CXX} ${MSVC_FLAGS} ${BOOST_CXX_FLAGS}")
 set(CMAKE_EXE_LINKER_FLAGS "${CMAKE_EXE_LINKER_FLAGS} ${MSVC_LD_FLAGS}")
 
+check_cxx_source_compiles("
+  #include <utility>
+  #include <type_traits>
+  std::make_index_sequence<0> t;
+  int main() { return 0; }"
+  HAVE_STD_INDEX_SEQUENCE
+)
+
 # use BEFORE to ensure local directories are used first,
 # ahead of system-installed libs
 include_directories(BEFORE ${PROJECT_BINARY_DIR}/simgear)

simgear/misc/CMakeLists.txt

@@ -56,6 +56,10 @@ add_executable(test_CSSBorder CSSBorder_test.cxx)
 add_test(CSSBorder ${EXECUTABLE_OUTPUT_PATH}/test_CSSBorder)
 target_link_libraries(test_CSSBorder ${TEST_LIBS})
 
+add_executable(test_integer_sequence integer_sequence_test.cxx)
+add_test(integer_sequence ${EXECUTABLE_OUTPUT_PATH}/test_integer_sequence)
+target_link_libraries(test_integer_sequence ${TEST_LIBS})
+
 add_executable(test_tabbed_values tabbed_values_test.cxx)
 add_test(tabbed_values ${EXECUTABLE_OUTPUT_PATH}/test_tabbed_values)
 target_link_libraries(test_tabbed_values ${TEST_LIBS})

simgear/misc/integer_sequence.hxx

@@ -0,0 +1,86 @@
+///@file
+/// Metaprogramming Integer sequence (Is in C++14 but not C++11)
+//
+// Copyright (C) 2017  Thomas Geymayer <tomgey@gmail.com>
+//
+// This library is free software; you can redistribute it and/or
+// modify it under the terms of the GNU Library General Public
+// License as published by the Free Software Foundation; either
+// version 2 of the License, or (at your option) any later version.
+//
+// This library is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+// Library General Public License for more details.
+//
+// You should have received a copy of the GNU Library General Public
+// License along with this library; if not, write to the Free Software
+// Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301, USA
+
+#ifndef SIMGEAR_MISC_INTEGER_SEQUENCE_HXX_
+#define SIMGEAR_MISC_INTEGER_SEQUENCE_HXX_
+
+#include <utility>
+#include <type_traits>
+
+#ifndef HAVE_STD_INDEX_SEQUENCE
+# include <cstddef>
+
+namespace std
+{
+  template<class T, T... Ints>
+  struct integer_sequence
+  {
+    static_assert(
+      std::is_integral<T>::value,
+      "std::integer_sequence can only be instantiated with an an integral type"
+    );
+
+    typedef T value_type;
+    static constexpr size_t size() noexcept { return sizeof...(Ints); }
+  };
+}
+
+namespace simgear { namespace detail
+{
+  template<class T, class Seq, T El>
+  struct append;
+
+  template<class T, T ... Ints, T Int>
+  struct append<T, std::integer_sequence<T, Ints...>, Int>
+  {
+    using type = std::integer_sequence<T, Ints..., Int>;
+  };
+
+  template<class T, std::size_t N>
+  struct sequence_gen
+  {
+    using type =
+      typename append<T, typename sequence_gen<T, N - 1>::type, N - 1>::type;
+  };
+
+  template<class T>
+  struct sequence_gen<T, 0>
+  {
+    using type = std::integer_sequence<T>;
+  };
+}}
+
+namespace std
+{
+  template<size_t... Ints>
+  using index_sequence = integer_sequence<size_t, Ints...>;
+
+  template<class T, size_t N>
+  using make_integer_sequence =
+    typename simgear::detail::sequence_gen<T, N>::type;
+
+  template<size_t N>
+  using make_index_sequence = make_integer_sequence<size_t, N>;
+
+  template<class... T>
+  using index_sequence_for = make_index_sequence<sizeof...(T)>;
+}
+#endif
+
+#endif /* SIMGEAR_MISC_INTEGER_SEQUENCE_HXX_ */

simgear/misc/integer_sequence_test.cxx

@@ -0,0 +1,47 @@
+#include "integer_sequence.hxx"
+
+#include <iostream>
+
+template<class T>
+void print(const T& v, std::size_t i)
+{
+  std::cout << "arg #" << i << ": '" << v << "', ";
+}
+
+template<typename ... Args, std::size_t ... Is>
+void doIt_impl(Args ... args, std::index_sequence<Is...>)
+{
+  std::initializer_list<char>{(print(args, Is), '0')...};
+}
+
+template<typename ... Args>
+void doIt(Args ... args)
+{
+  static_assert(sizeof...(Args) == std::index_sequence_for<Args...>::size(), "");
+
+  doIt_impl<Args...>(args..., std::index_sequence_for<Args...>{});
+}
+
+int main(int argc, char* argv[])
+{
+  static_assert(std::is_same<std::integer_sequence<char>::value_type, char>::value, "");
+  static_assert(std::is_same<std::integer_sequence<long long>::value_type, long long>::value, "");
+  static_assert(std::is_same<std::index_sequence<>::value_type, std::size_t>::value, "");
+
+  static_assert(std::is_same<std::make_index_sequence<0>, std::index_sequence<>>::value, "");
+  static_assert(std::is_same<std::make_index_sequence<1>, std::index_sequence<0>>::value, "");
+  static_assert(std::is_same<std::make_index_sequence<2>, std::index_sequence<0, 1>>::value, "");
+  static_assert(std::is_same<std::make_index_sequence<3>, std::index_sequence<0, 1, 2>>::value, "");
+  static_assert(std::is_same<std::make_index_sequence<4>, std::index_sequence<0, 1, 2, 3>>::value, "");
+  static_assert(std::is_same<std::make_index_sequence<5>, std::index_sequence<0, 1, 2, 3, 4>>::value, "");
+  static_assert(std::is_same<std::make_index_sequence<6>, std::index_sequence<0, 1, 2, 3, 4, 5>>::value, "");
+  static_assert(std::is_same<std::make_index_sequence<7>, std::index_sequence<0, 1, 2, 3, 4, 5, 6>>::value, "");
+  static_assert(std::is_same<std::make_index_sequence<8>, std::index_sequence<0, 1, 2, 3, 4, 5, 6, 7>>::value, "");
+
+  static_assert(std::make_index_sequence<5>::size() == 5, "");
+  static_assert(std::index_sequence_for<float, int, double>::size() == 3, "");
+
+  std::cout << std::make_integer_sequence<int, 5>::size() << std::endl;
+  doIt(1, 2, 3, "hallo", 3.4, 3.52f);
+  return 0;
+}

simgear/simgear_config_cmake.h.in

@@ -15,7 +15,7 @@
 #cmakedefine HAVE_WINDOWS_H
 #cmakedefine HAVE_MKDTEMP
 #cmakedefine HAVE_AL_EXT_H
-
+#cmakedefine HAVE_STD_INDEX_SEQUENCE
 
 #cmakedefine GCC_ATOMIC_BUILTINS_FOUND