CXX11Workarounds.h
00001 // This file is part of Eigen, a lightweight C++ template library
00002 // for linear algebra.
00003 //
00004 // Copyright (C) 2013 Christian Seiler <christian@iwakd.de>
00005 //
00006 // This Source Code Form is subject to the terms of the Mozilla
00007 // Public License v. 2.0. If a copy of the MPL was not distributed
00008 // with this file, You can obtain one at http://mozilla.org/MPL/2.0/.
00009 
00010 #ifndef EIGEN_CXX11WORKAROUNDS_H
00011 #define EIGEN_CXX11WORKAROUNDS_H
00012 
00013 /* COMPATIBILITY CHECKS
00014  * (so users of compilers that are too old get some realistic error messages)
00015  */
00016 #if defined(__INTEL_COMPILER) && (__INTEL_COMPILER < 1310)
00017 #error Intel Compiler only supports required C++ features since version 13.1.
00018 // note that most stuff in principle works with 13.0 but when combining
00019 // some features, at some point 13.0 will just fail with an internal assertion
00020 #elif defined(__GNUC__) && !defined(__clang__) && !defined(__INTEL_COMPILER) && (__GNUC__ < 4 || (__GNUC__ == 4 && __GNUC_MINOR__ < 6))
00021 // G++ < 4.6 by default will continue processing the source files - even if we use #error to make
00022 // it error out. For this reason, we use the pragma to make sure G++ aborts at the first error
00023 // it sees. Unfortunately, that is still not our #error directive, but at least the output is
00024 // short enough the user has a chance to see that the compiler version is not sufficient for
00025 // the funky template mojo we use.
00026 #pragma GCC diagnostic error "-Wfatal-errors"
00027 #error GNU C++ Compiler (g++) only supports required C++ features since version 4.6.
00028 #endif
00029 
00030 /* Check that the compiler at least claims to support C++11. It might not be sufficient
00031  * because the compiler may not implement it correctly, but at least we'll know.
00032  * On the other hand, visual studio still doesn't claim to support C++11 although it's
00033  * compliant enugh for our purpose.
00034  */
00035 #if (__cplusplus <= 199711L) && (EIGEN_COMP_MSVC < 1900)
00036 #if defined(__GNUC__) && !defined(__clang__) && !defined(__INTEL_COMPILER)
00037 #pragma GCC diagnostic error "-Wfatal-errors"
00038 #endif
00039 #error This library needs at least a C++11 compliant compiler. If you use g++/clang, please enable the -std=c++11 compiler flag. (-std=c++0x on older versions.)
00040 #endif
00041 
00042 namespace Eigen {
00043 
00044 namespace internal {
00045 
00046 /* std::get is only constexpr in C++14, not yet in C++11
00047  */
00048 
00049 
00050 template<std::size_t I, class T> constexpr inline T&       array_get(std::vector<T>&       a) { return a[I]; }
00051 template<std::size_t I, class T> constexpr inline T&&      array_get(std::vector<T>&&      a) { return a[I]; }
00052 template<std::size_t I, class T> constexpr inline T const& array_get(std::vector<T> const& a) { return a[I]; }
00053 
00054 /* Suppose you have a template of the form
00055  * template<typename T> struct X;
00056  * And you want to specialize it in such a way:
00057  *    template<typename S1, typename... SN> struct X<Foo<S1, SN...>> { ::: };
00058  *    template<>                            struct X<Foo<>>          { ::: };
00059  * This will work in Intel's compiler 13.0, but only to some extent in g++ 4.6, since
00060  * g++ can only match templates called with parameter packs if the number of template
00061  * arguments is not a fixed size (so inside the first specialization, referencing
00062  * X<Foo<Sn...>> will fail in g++). On the other hand, g++ will accept the following:
00063  *    template<typename S...> struct X<Foo<S...>> { ::: }:
00064  * as an additional (!) specialization, which will then only match the empty case.
00065  * But Intel's compiler 13.0 won't accept that, it will only accept the empty syntax,
00066  * so we have to create a workaround for this.
00067  */
00068 #if defined(__GNUC__) && !defined(__INTEL_COMPILER)
00069 #define EIGEN_TPL_PP_SPEC_HACK_DEF(mt, n)    mt... n
00070 #define EIGEN_TPL_PP_SPEC_HACK_DEFC(mt, n)   , EIGEN_TPL_PP_SPEC_HACK_DEF(mt, n)
00071 #define EIGEN_TPL_PP_SPEC_HACK_USE(n)        n...
00072 #define EIGEN_TPL_PP_SPEC_HACK_USEC(n)       , n...
00073 #else
00074 #define EIGEN_TPL_PP_SPEC_HACK_DEF(mt, n)
00075 #define EIGEN_TPL_PP_SPEC_HACK_DEFC(mt, n)
00076 #define EIGEN_TPL_PP_SPEC_HACK_USE(n)
00077 #define EIGEN_TPL_PP_SPEC_HACK_USEC(n)
00078 #endif
00079 
00080 } // end namespace internal
00081 
00082 } // end namespace Eigen
00083 
00084 #endif // EIGEN_CXX11WORKAROUNDS_H
00085 
00086 /*
00087  * kate: space-indent on; indent-width 2; mixedindent off; indent-mode cstyle;
00088  */
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