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59 lines
1.5 KiB
C++
59 lines
1.5 KiB
C++
// (C) Copyright John Maddock and Dave Abrahams 2002.
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// Use, modification and distribution are subject to the
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// Boost Software License, Version 1.0. (See accompanying file
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// LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
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// See http://www.boost.org/libs/config for most recent version.
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// MACRO: BOOST_NO_IS_ABSTRACT
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// TITLE: is_abstract implementation technique
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// DESCRIPTION: Some compilers can't handle the code used for is_abstract even if they support SFINAE.
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namespace boost_no_is_abstract{
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#if defined(BOOST_CODEGEARC)
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template<class T>
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struct is_abstract_test
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{
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enum{ value = __is_abstract(T) };
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};
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#else
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template<class T>
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struct is_abstract_test
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{
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// Deduction fails if T is void, function type,
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// reference type (14.8.2/2)or an abstract class type
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// according to review status issue #337
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//
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template<class U>
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static double check_sig(U (*)[1]);
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template<class U>
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static char check_sig(...);
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#if defined(__GNUC__) && (__GNUC__ < 10)
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enum{ s1 = sizeof(is_abstract_test<T>::template check_sig<T>(0)) };
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#else
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enum{ s1 = sizeof(check_sig<T>(0)) };
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#endif
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enum{ value = (s1 == sizeof(char)) };
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};
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#endif
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struct non_abstract{};
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struct abstract{ virtual void foo() = 0; };
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int test()
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{
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#if defined(__GNUC__) && (__GNUC__ > 10)
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// GCC-11 fails the above test, but this is irrelevant in any case:
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return 0;
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#else
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return static_cast<bool>(is_abstract_test<non_abstract>::value) == static_cast<bool>(is_abstract_test<abstract>::value);
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#endif
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}
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}
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