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99e2df0090
This patch simplifies gdbsupport/traits.h by reusing some C++17 type traits. I kept the local names, since they are generally better. Bug: https://sourceware.org/bugzilla/show_bug.cgi?id=31423 Approved-By: Simon Marchi <simon.marchi@efficios.com>
114 lines
3.7 KiB
C++
114 lines
3.7 KiB
C++
/* Copyright (C) 2017-2024 Free Software Foundation, Inc.
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This file is part of GDB.
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This program is free software; you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation; either version 3 of the License, or
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(at your option) any later version.
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This program is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with this program. If not, see <http://www.gnu.org/licenses/>. */
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#ifndef GDBSUPPORT_TRAITS_H
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#define GDBSUPPORT_TRAITS_H
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#include <type_traits>
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namespace gdb {
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/* Implementation of the detection idiom:
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- http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2015/n4502.pdf
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- http://en.cppreference.com/w/cpp/experimental/is_detected
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*/
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struct nonesuch
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{
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nonesuch () = delete;
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~nonesuch () = delete;
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nonesuch (const nonesuch &) = delete;
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void operator= (const nonesuch &) = delete;
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};
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namespace detection_detail {
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/* Implementation of the detection idiom (negative case). */
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template<typename Default, typename AlwaysVoid,
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template<typename...> class Op, typename... Args>
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struct detector
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{
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using value_t = std::false_type;
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using type = Default;
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};
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/* Implementation of the detection idiom (positive case). */
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template<typename Default, template<typename...> class Op, typename... Args>
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struct detector<Default, std::void_t<Op<Args...>>, Op, Args...>
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{
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using value_t = std::true_type;
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using type = Op<Args...>;
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};
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/* Detect whether Op<Args...> is a valid type, use Default if not. */
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template<typename Default, template<typename...> class Op,
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typename... Args>
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using detected_or = detector<Default, void, Op, Args...>;
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/* Op<Args...> if that is a valid type, otherwise Default. */
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template<typename Default, template<typename...> class Op,
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typename... Args>
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using detected_or_t
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= typename detected_or<Default, Op, Args...>::type;
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} /* detection_detail */
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template<template<typename...> class Op, typename... Args>
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using is_detected
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= typename detection_detail::detector<nonesuch, void, Op, Args...>::value_t;
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template<template<typename...> class Op, typename... Args>
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using detected_t
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= typename detection_detail::detector<nonesuch, void, Op, Args...>::type;
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template<typename Default, template<typename...> class Op, typename... Args>
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using detected_or = detection_detail::detected_or<Default, Op, Args...>;
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template<typename Default, template<typename...> class Op, typename... Args>
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using detected_or_t = typename detected_or<Default, Op, Args...>::type;
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template<typename Expected, template<typename...> class Op, typename... Args>
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using is_detected_exact = std::is_same<Expected, detected_t<Op, Args...>>;
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template<typename To, template<typename...> class Op, typename... Args>
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using is_detected_convertible
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= std::is_convertible<detected_t<Op, Args...>, To>;
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/* A few trait helpers -- standard traits but with slightly nicer
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names. Uppercase because "and/or", etc. are reserved keywords. */
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template<typename Predicate>
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using Not = std::negation<Predicate>;
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template<typename ...T>
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using Or = std::disjunction<T...>;
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template<typename ...T>
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using And = std::conjunction<T...>;
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/* Concepts-light-like helper to make SFINAE logic easier to read. */
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template<typename Condition>
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using Requires = typename std::enable_if<Condition::value, void>::type;
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}
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template<typename T>
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using RequireLongest = gdb::Requires<gdb::Or<std::is_same<T, LONGEST>,
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std::is_same<T, ULONGEST>>>;
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#endif /* GDBSUPPORT_TRAITS_H */
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