src/util/CXX11Workarounds.h

0001 // This file is part of Eigen, a lightweight C++ template library
0002 // for linear algebra.
0003 //
0004 // Copyright (C) 2013 Christian Seiler <christian@iwakd.de>
0005 //
0006 // This Source Code Form is subject to the terms of the Mozilla
0007 // Public License v. 2.0. If a copy of the MPL was not distributed
0008 // with this file, You can obtain one at http://mozilla.org/MPL/2.0/.
0009
0010 #ifndef EIGEN_CXX11WORKAROUNDS_H
0011 #define EIGEN_CXX11WORKAROUNDS_H
0012
0013 /* COMPATIBILITY CHECKS
0014  * (so users of compilers that are too old get some realistic error messages)
0015  */
0016 #if defined(__INTEL_COMPILER) && (__INTEL_COMPILER < 1310)
0017 #error Intel Compiler only supports required C++ features since version 13.1.
0018 // note that most stuff in principle works with 13.0 but when combining
0019 // some features, at some point 13.0 will just fail with an internal assertion
0020 #elif defined(__GNUC__) && !defined(__clang__) && !defined(__INTEL_COMPILER) && (__GNUC__ < 4 || (__GNUC__ == 4 && __GNUC_MINOR__ < 6))
0021 // G++ < 4.6 by default will continue processing the source files - even if we use #error to make
0022 // it error out. For this reason, we use the pragma to make sure G++ aborts at the first error
0023 // it sees. Unfortunately, that is still not our #error directive, but at least the output is
0024 // short enough the user has a chance to see that the compiler version is not sufficient for
0025 // the funky template mojo we use.
0026 #pragma GCC diagnostic error "-Wfatal-errors"
0027 #error GNU C++ Compiler (g++) only supports required C++ features since version 4.6.
0028 #endif
0029
0030 /* Check that the compiler at least claims to support C++11. It might not be sufficient
0031  * because the compiler may not implement it correctly, but at least we'll know.
0032  * On the other hand, visual studio still doesn't claim to support C++11 although it's
0033  * compliant enugh for our purpose.
0034  */
0035 #if (EIGEN_COMP_CXXVER < 11)
0036 #if defined(__GNUC__) && !defined(__clang__) && !defined(__INTEL_COMPILER)
0037 #pragma GCC diagnostic error "-Wfatal-errors"
0038 #endif
0039 #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.)
0040 #endif
0041
0042 namespace Eigen {
0043
0044 namespace internal {
0045
0046 /* std::get is only constexpr in C++14, not yet in C++11
0047  */
0048
0049
0050 template<std::size_t I_, class T> constexpr inline T&       array_get(std::vector<T>&       a) { return a[I_]; }
0051 template<std::size_t I_, class T> constexpr inline T&&      array_get(std::vector<T>&&      a) { return a[I_]; }
0052 template<std::size_t I_, class T> constexpr inline T const& array_get(std::vector<T> const& a) { return a[I_]; }
0053
0054 /* Suppose you have a template of the form
0055  * template<typename T> struct X;
0056  * And you want to specialize it in such a way:
0057  *    template<typename S1, typename... SN> struct X<Foo<S1, SN...>> { ::: };
0058  *    template<>                            struct X<Foo<>>          { ::: };
0059  * This will work in Intel's compiler 13.0, but only to some extent in g++ 4.6, since
0060  * g++ can only match templates called with parameter packs if the number of template
0061  * arguments is not a fixed size (so inside the first specialization, referencing
0062  * X<Foo<Sn...>> will fail in g++). On the other hand, g++ will accept the following:
0063  *    template<typename S...> struct X<Foo<S...>> { ::: }:
0064  * as an additional (!) specialization, which will then only match the empty case.
0065  * But Intel's compiler 13.0 won't accept that, it will only accept the empty syntax,
0066  * so we have to create a workaround for this.
0067  */
0068 #if defined(__GNUC__) && !defined(__INTEL_COMPILER)
0069 #define EIGEN_TPL_PP_SPEC_HACK_DEF(mt, n)    mt... n
0070 #define EIGEN_TPL_PP_SPEC_HACK_DEFC(mt, n)   , EIGEN_TPL_PP_SPEC_HACK_DEF(mt, n)
0071 #define EIGEN_TPL_PP_SPEC_HACK_USE(n)        n...
0072 #define EIGEN_TPL_PP_SPEC_HACK_USEC(n)       , n...
0073 #else
0074 #define EIGEN_TPL_PP_SPEC_HACK_DEF(mt, n)
0075 #define EIGEN_TPL_PP_SPEC_HACK_DEFC(mt, n)
0076 #define EIGEN_TPL_PP_SPEC_HACK_USE(n)
0077 #define EIGEN_TPL_PP_SPEC_HACK_USEC(n)
0078 #endif
0079
0080 } // end namespace internal
0081
0082 } // end namespace Eigen
0083
0084 #endif // EIGEN_CXX11WORKAROUNDS_H
0085
0086 /*
0087  * kate: space-indent on; indent-width 2; mixedindent off; indent-mode cstyle;
0088  */