gls_cpp_lang_support.h

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/*! \file
  \brief  Macros and helper code to determine what subset of C++11/14/17 is available.

  \par Copyright Information

  Copyright (c) 2016 The DiSTI Corporation.<br>
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  All rights reserved.<br>

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  NO WARRANTY. THE SOFTWARE IS PROVIDED "AS-IS," WITHOUT WARRANTY OF ANY KIND,
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  The aforementioned terms and restrictions are governed by the laws of the
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*/

#ifndef INCLUDED_GLS_CPP_LANG_SUPPORT_H
#define INCLUDED_GLS_CPP_LANG_SUPPORT_H

// Conditional C++11 support
//
// We use a subset of C++11 features to improve efficiency and correctness of code.
//
// We attempt to detect compiler support, but for unusual configurations, it can be 
// enabled with project-level defines. Define DISTI_HAS_CPP11 to enable all features. 
// Enable specific features by defining any of the following:
//
//   DISTI_HAS_RVAL_REFS            // For rvalue references
//   DISTI_HAS_METHOD_OVERRIDE      // For "override" and "final" keywords
//   DISTI_HAS_SPECIAL_MEM_FUN_DEL  // For "= delete"
//   DISTI_HAS_TYPE_TRAITS          // For compile-time checking via type-traits
//   DISTI_HAS_STATIC_ASSERT        // For static_assert support
//
// If our detection is incorrect, override it with a corresponding "NO" define:
//
//   DISTI_NO_RVAL_REFS             // For rvalue references
//   DISTI_NO_METHOD_OVERRIDE       // For "override" and "final" keywords
//   DISTI_NO_METHOD_FINAL          // For "final" keyword
//   DISTI_NO_SPECIAL_MEM_FUN_DEL   // For "= delete"
//   DISTI_NO_TYPE_TRAITS           // For compile-time checking via type-traits
//   DISTI_NO_STATIC_ASSERT         // For static_assert support

/////////////////////////////////////////////////////////////////////////////////////
// Microsoft C++ Compiler -- https://msdn.microsoft.com/en-us/library/hh567368.aspx
/////////////////////////////////////////////////////////////////////////////////////
#if defined(_MSC_VER)
    #if _MSC_VER >= 1700 // >= VS2012
        #define DISTI_HAS_RVAL_REFS
        #define DISTI_HAS_METHOD_OVERRIDE
        #define DISTI_HAS_TYPE_TRAITS
        #define DISTI_HAS_STATIC_ASSERT
    #endif
    #if _MSC_VER >= 1800 // >= VS2013
        #define DISTI_HAS_SPECIAL_MEM_FUN_DEL
    #endif
////////////////////////////////////////////////////////////////////////////////
// GCC versions -- https://gcc.gnu.org/projects/cxx-status.html#cxx11
////////////////////////////////////////////////////////////////////////////////
#elif defined( __GNUC__ )
    // __cpp_rvalue_references doesn't seem to be defined in GCC, despite the documentation, so we have an alternative check also
    #if __cpp_rvalue_references >= 200610 || ( (__GNUC__ > 4 || (__GNUC__ == 4 && __GNUC_MINOR__ >= 3)) && ( defined(__GXX_EXPERIMENTAL_CXX0X__) || __cplusplus >= 201103L ) )
        #define DISTI_HAS_RVAL_REFS
    #endif
    #if __cpp_static_assert >= 200410 && ( defined(__GXX_EXPERIMENTAL_CXX0X__) || __cplusplus >= 201103L )
        #define DISTI_HAS_STATIC_ASSERT
    #endif
    #if (__GNUC__ > 4 || (__GNUC__ == 4 && __GNUC_MINOR__ >= 7)) && ( defined(__GXX_EXPERIMENTAL_CXX0X__) || __cplusplus >= 201103L )
        #define DISTI_HAS_METHOD_OVERRIDE

        // This actually depends on which standard library is in use, but it's a safe bet.
        #define DISTI_HAS_TYPE_TRAITS
    #endif
    #if (__GNUC__ > 4 || (__GNUC__ == 4 && __GNUC_MINOR__ >= 4)) && ( defined(__GXX_EXPERIMENTAL_CXX0X__) || __cplusplus >= 201103L )
        #define DISTI_HAS_SPECIAL_MEM_FUN_DEL
    #endif
////////////////////////////////////////////////////////////////////////////////
// Clang versions -- http://clang.llvm.org/cxx_status.html
////////////////////////////////////////////////////////////////////////////////
#elif defined( __clang__ )
    #if __has_feature(cxx_rvalue_references)
        #define DISTI_HAS_RVAL_REFS
    #endif
    #if __has_feature(cxx_override_control)
        #define DISTI_HAS_METHOD_OVERRIDE
    #endif
    #if __has_feature(cxx_defaulted_functions) && __has_feature(cxx_deleted_functions)
        #define DISTI_HAS_SPECIAL_MEM_FUN_DEL
    #endif
    #if __has_feature(cxx_static_assert)
        #define DISTI_HAS_STATIC_ASSERT
    #endif

    // This actually depends on which standard library is in use, but it's a safe bet.
    #define DISTI_HAS_TYPE_TRAITS
#endif

///////////////////////////////////////////////////////////////////////////////////////////////////
// Shortcut for unrecognized compilers
///////////////////////////////////////////////////////////////////////////////////////////////////
#ifdef DISTI_HAS_CPP11 // A single switch to enable everything since compiler is highly compliant
    // These macros can help with cross-platform portability
    #define DISTI_IF_HAS_CPP11( x )         x
    #define DISTI_IF_HAS_CPP11_ELSE( x, y ) x

    #define DISTI_HAS_RVAL_REFS
    #define DISTI_HAS_METHOD_OVERRIDE
    #define DISTI_HAS_SPECIAL_MEM_FUN_DEL
    #define DISTI_HAS_TYPE_TRAITS
    #define DISTI_HAS_STATIC_ASSERT
#else // Not fully C++11; some features may be enabled piecemeal
    // These macros can help with cross-platform portability
    #define DISTI_IF_HAS_CPP11( x )
    #define DISTI_IF_HAS_CPP11_ELSE( x, y ) y
#endif

///////////////////////////////////////////////////////////////////////////////////////////////////
// Individual C++11 features. See comment above on DISTI_NO_* vs. DISTI_HAS_* macros.
///////////////////////////////////////////////////////////////////////////////////////////////////
#if !defined( DISTI_NO_RVAL_REFS ) && defined( DISTI_HAS_RVAL_REFS )
    #include <utility>
    #define DISTI_RVAL_MOVE(x)    std::move(x)
    #define DISTI_IF_HAS_RVAL_REFS_ELSE( x, y ) x
#else
    #undef DISTI_HAS_RVAL_REFS
    #define DISTI_RVAL_MOVE(x)    (x)
    #define DISTI_IF_HAS_RVAL_REFS_ELSE( x, y ) y
#endif

///////////////////////////////////////////////////////////////////////////////////////////////////
#if !defined( DISTI_NO_METHOD_OVERRIDE ) && defined( DISTI_HAS_METHOD_OVERRIDE )
    // Add this to the end of an overridden method
    #define DISTI_METHOD_OVERRIDE override
    // Add this to the end of a method that should not be overridden
    #define DISTI_METHOD_FINAL final
#else
    #undef DISTI_HAS_METHOD_OVERRIDE
    #define DISTI_METHOD_OVERRIDE
    #define DISTI_METHOD_FINAL
#endif

///////////////////////////////////////////////////////////////////////////////////////////////////
#if !defined( DISTI_NO_SPECIAL_MEM_FUN_DEL ) && defined( DISTI_HAS_SPECIAL_MEM_FUN_DEL )
    // Add these to the end of special member functions to delete them.
    #define DISTI_SPECIAL_MEM_FUN_DELETE  = delete
#else
    #undef DISTI_HAS_SPECIAL_MEM_FUN_DEL
    #define DISTI_SPECIAL_MEM_FUN_DELETE
#endif

///////////////////////////////////////////////////////////////////////////////////////////////////
#if !defined( DISTI_NO_TYPE_TRAITS ) && defined( DISTI_HAS_TYPE_TRAITS )
    // Use this by including <type_traits> and then providing a default, e.g.,
    //   DISTI_IF_HAS_TYPE_TRAITS_ELSE( std::is_const<T>::value, false )
    #define DISTI_IF_HAS_TYPE_TRAITS_ELSE( x, y ) x
#else
    #undef DISTI_HAS_TYPE_TRAITS
    #define DISTI_IF_HAS_TYPE_TRAITS_ELSE( x, y ) y

    namespace disti
    {
        // The _cppLangSupportDetail namespace is here to hide implementation details, mostly for things 
        // that are standard but not available on all supported platforms.
        namespace _cppLangSupportDetail
        {
            /// Replacement for std::is_convertible, adapted from Loki 0.1.7.
            /////////////////////////////////////////////////////////////////////////////////
            /// \copyright The Loki Library, Copyright (c) 2001 by Andrei Alexandrescu<br />
            /// This code accompanies the book: 
            /// Alexandrescu, Andrei. "Modern C++ Design: Generic Programming and Design 
            ///     Patterns Applied". Copyright (c) 2001. Addison-Wesley.<br />
            /// Permission to use, copy, modify, distribute and sell this software for any 
            ///     purpose is hereby granted without fee, provided that the above copyright 
            ///     notice appear in all copies and that both that copyright notice and this 
            ///     permission notice appear in supporting documentation.<br />
            /// The author or Addison-Welsey Longman make no representations about the 
            ///     suitability of this software for any purpose. It is provided "as is" 
            ///     without express or implied warranty.<br />
            /////////////////////////////////////////////////////////////////////////////////
            template <class T, class U>
            struct is_convertible
            {
            private:
                typedef char Small;
                struct Big { char dummy[2]; };
                static Big   Test(...);
                static Small Test(U);
                static T MakeT();
            public:
                enum { value = sizeof(Small) == sizeof((Test(MakeT()))) };
            };

            template <class T> struct is_convertible<T,    T   > { enum { value = true  }; }; //< Replacement for std::is_convertible, adapted from Loki 0.1.7.
            template <class T> struct is_convertible<void, T   > { enum { value = false }; }; //< Replacement for std::is_convertible, adapted from Loki 0.1.7.
            template <class T> struct is_convertible<T,    void> { enum { value = false }; }; //< Replacement for std::is_convertible, adapted from Loki 0.1.7.
            template<>         struct is_convertible<void, void> { enum { value = true  }; }; //< Replacement for std::is_convertible, adapted from Loki 0.1.7.
        }
    }
#endif

///////////////////////////////////////////////////////////////////////////////////////////////////
#if defined( DISTI_NO_STATIC_ASSERT )
    #undef DISTI_HAS_STATIC_ASSERT
    #define DISTI_STATIC_ASSERT( expr, msg )
#else
    #define DISTI_PREPROC_STRINGIFY_HELPER(s) #s
    #define DISTI_PREPROC_STRINGIFY(s) DISTI_PREPROC_STRINGIFY_HELPER(s)

    #if defined( DISTI_HAS_STATIC_ASSERT )
         /// \brief Uses C++11's static_assert() because it is available on this platform.
         /// \param expr a compile-time integral or pointer expression
         /// \param msg  a C identifier that will appear in compiler diagnostics
         /// \note For older compilers' benefit, \a msg should be a C identifier such as:
         ///    DISTI_STATIC_ASSERT( (std::is_convertible<T*,ConvertsTo*>::value), class_does_not_inherit_from_##ConvertsTo )
         ///  which shows a compile-time error that typically includes: "ERROR_class_does_not_inherit_from_Group".
         ///  If it is not a C identifier, you may get spurious error messages at compile time compilers without static_assert.
        #define DISTI_STATIC_ASSERT( expr, msg ) static_assert( expr, DISTI_PREPROC_STRINGIFY(msg) )
    #else
        namespace disti
        {
            namespace _cppLangSupportDetail
            {
                // Helpers for DISTI_STATIC_ASSERT
                // \note Adapted from Loki 0.1.7.
                template<int> struct CompileTimeError;
                template<> struct CompileTimeError<true> { CompileTimeError() {} };
            }
        }

        /// \brief Poor man's version of C++11's static_assert()
        /// \param expr a compile-time integral or pointer expression
        /// \param msg  a C identifier that will appear in compiler diagnostics
        /// \note For older compilers' benefit, \a msg should be a C identifier such as:
        ///    DISTI_STATIC_ASSERT( (std::is_convertible<T*,ConvertsTo*>::value), class_does_not_inherit_from_##ConvertsTo )
        ///  which shows a compile-time error that typically includes: "ERROR_class_does_not_inherit_from_Group".
        ///  If it is not a C identifier, you may get spurious error messages at compile time compilers without static_assert.
        /// \note Adapted from Loki 0.1.7.
       #define DISTI_STATIC_ASSERT(expr, msg) \
            { \
                ::disti::_cppLangSupportDetail::CompileTimeError<((expr) != 0)> ERROR_##msg; \
                (void) ERROR_##msg; \
            } 
   #endif
#endif

////////////////////////////////////////////////////////////////////////////////
/// Convenience macro to check that one type converts to another at compile-time.
/// \param T A class to check
/// \param ConvertsTo A class to test T* against to verify that it can be 
///                   converted to ConvertsTo* without a cast.
/// \note This macro appears here for grouping with like code, but macros 
///       aren't scoped to namespace.
////////////////////////////////////////////////////////////////////////////////
#ifdef DISTI_HAS_TYPE_TRAITS
    #define DISTI_STATIC_ASSERT_IS_CONVERTIBLE_TO( T, ConvertsTo ) DISTI_STATIC_ASSERT( (std::is_convertible<T*,ConvertsTo*>::value), class_does_not_inherit_from_##ConvertsTo );
#else
    #define DISTI_STATIC_ASSERT_IS_CONVERTIBLE_TO( T, ConvertsTo ) DISTI_STATIC_ASSERT( (::disti::_cppLangSupportDetail::is_convertible< T*, ConvertsTo* >::value), class_does_not_inherit_from_##ConvertsTo )
#endif

#endif