123 lines
4.9 KiB
Diff
123 lines
4.9 KiB
Diff
From 0487cca29e352e8f16bbd91fda38e76e39a0ed28 Mon Sep 17 00:00:00 2001
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From: Louis Dionne <ldionne.2@gmail.com>
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Date: Tue, 15 Jun 2021 14:40:01 -0400
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Subject: [PATCH] Work around broken integration with latest libc++. (#1635)
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* Work around broken integration with latest libc++.
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In newer versions of libc++, the base template of std::iterator_traits
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provides a member typedef called __primary_template which is an alias
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to the std::iterator_traits specialization itself. This fix works with
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both the old version of libc++ and the new one.
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Fixes issue #1633.
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* Fix is_std_iterator_traits_specialized_v on MSVC
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It used to pretend that std::iterator_traits<T*> is a user-defined
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specialization, which isn't the case. This is due to MSVC's
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iterator_traits<T*> specialization not posing as the base template.
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---
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include/std/detail/associated_types.hpp | 22 +++++++++++-----
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test/CMakeLists.txt | 1 +
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test/bug1633.cpp | 34 +++++++++++++++++++++++++
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3 files changed, 51 insertions(+), 6 deletions(-)
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create mode 100644 test/bug1633.cpp
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diff --git a/include/std/detail/associated_types.hpp b/include/std/detail/associated_types.hpp
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index b642166d4..449a3f91c 100644
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--- a/include/std/detail/associated_types.hpp
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+++ b/include/std/detail/associated_types.hpp
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@@ -265,11 +265,22 @@ namespace ranges
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template<typename I>
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char is_std_iterator_traits_specialized_impl_(void *);
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#elif defined(_LIBCPP_VERSION)
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- template<typename I, bool B>
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- char (
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- &is_std_iterator_traits_specialized_impl_(std::__iterator_traits<I, B> *))[2];
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+ // In older versions of libc++, the base template inherits from std::__iterator_traits<typename, bool>.
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+ template<template<typename, bool> class IteratorTraitsBase, typename I, bool B>
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+ char (&libcpp_iterator_traits_base_impl(IteratorTraitsBase<I, B> *))[2];
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+ template<template<typename, bool> class IteratorTraitsBase, typename I>
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+ char libcpp_iterator_traits_base_impl(void *);
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+
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+ // In newer versions, the base template has only one template parameter and provides the
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+ // __primary_template typedef which aliases the iterator_traits specialization.
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+ template<template<typename> class, typename I>
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+ char (&libcpp_iterator_traits_base_impl(typename std::iterator_traits<I>::__primary_template *))[2];
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+ template<template<typename> class, typename I>
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+ char libcpp_iterator_traits_base_impl(void *);
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+
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template<typename I>
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- char is_std_iterator_traits_specialized_impl_(void *);
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+ auto is_std_iterator_traits_specialized_impl_(std::iterator_traits<I>* traits)
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+ -> decltype(libcpp_iterator_traits_base_impl<std::__iterator_traits, I>(traits));
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#elif defined(_MSVC_STL_VERSION)
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template<typename I>
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char (&is_std_iterator_traits_specialized_impl_(
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@@ -287,14 +298,13 @@ namespace ranges
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RANGES_INLINE_VAR constexpr bool is_std_iterator_traits_specialized_v =
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1 == sizeof(is_std_iterator_traits_specialized_impl_<I>(
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static_cast<std::iterator_traits<I> *>(nullptr)));
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-
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+#endif
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// The standard iterator_traits<T *> specialization(s) do not count
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// as user-specialized. This will no longer be necessary in C++20.
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// This helps with `T volatile*` and `void *`.
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template<typename T>
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RANGES_INLINE_VAR constexpr bool is_std_iterator_traits_specialized_v<T *> =
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false;
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-#endif
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} // namespace detail
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/// \endcond
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} // namespace ranges
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diff --git a/test/CMakeLists.txt b/test/CMakeLists.txt
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index 889f314af..2c2b7c09c 100644
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--- a/test/CMakeLists.txt
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+++ b/test/CMakeLists.txt
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@@ -19,3 +19,4 @@ rv3_add_test(test.bug474 bug474 bug474.cpp)
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rv3_add_test(test.bug566 bug566 bug566.cpp)
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rv3_add_test(test.bug1322 bug1322 bug1322.cpp)
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rv3_add_test(test.bug1335 bug1335 bug1335.cpp)
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+rv3_add_test(test.bug1633 bug1633 bug1633.cpp)
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diff --git a/test/bug1633.cpp b/test/bug1633.cpp
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new file mode 100644
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index 000000000..be52420ad
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--- /dev/null
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+++ b/test/bug1633.cpp
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@@ -0,0 +1,34 @@
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+// Range v3 library
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+//
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+// Use, modification and distribution is subject to the
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+// Boost Software License, Version 1.0. (See accompanying
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+// file LICENSE_1_0.txt or copy at
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+// http://www.boost.org/LICENSE_1_0.txt)
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+//
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+// Project home: https://github.com/ericniebler/range-v3
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+
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+#include <cstddef>
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+#include <iterator>
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+#include <range/v3/iterator.hpp>
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+
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+struct X { };
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+
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+namespace std {
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+ template<> struct iterator_traits<X> { };
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+}
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+
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+struct Y {
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+ using difference_type = std::ptrdiff_t;
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+ using value_type = int;
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+ using pointer = int*;
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+ using reference = int&;
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+ using iterator_category = std::forward_iterator_tag;
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+};
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+
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+static_assert(ranges::detail::is_std_iterator_traits_specialized_v<X>, "");
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+static_assert(!ranges::detail::is_std_iterator_traits_specialized_v<Y>, "");
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+static_assert(!ranges::detail::is_std_iterator_traits_specialized_v<int*>, "");
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+
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+int main()
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+{
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+}
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