re PR libstdc++/56267 (unordered containers require Assignable hash function)
PR libstdc++/56267 * include/bits/hashtable.h (__cache_default): Do not depend on whether the hash function is DefaultConstructible or CopyAssignable. (_Hashtable): Adjust static assertions. * doc/xml/manual/containers.xml (containers.unordered.cache): Update. * testsuite/23_containers/unordered_set/instantiation_neg.cc: Adjust dg-error line number. * testsuite/23_containers/unordered_set/ not_default_constructible_hash_neg.cc: Remove. From-SVN: r206904
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Jonathan Wakely
Jonathan Wakely
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@ -1,3 +1,15 @@
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2014-01-21 Jonathan Wakely <jwakely@redhat.com>
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PR libstdc++/56267
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* include/bits/hashtable.h (__cache_default): Do not depend on
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whether the hash function is DefaultConstructible or CopyAssignable.
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(_Hashtable): Adjust static assertions.
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* doc/xml/manual/containers.xml (containers.unordered.cache): Update.
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* testsuite/23_containers/unordered_set/instantiation_neg.cc: Adjust
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dg-error line number.
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* testsuite/23_containers/unordered_set/
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not_default_constructible_hash_neg.cc: Remove.
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2014-01-20 François Dumont <fdumont@gcc.gnu.org>
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* scripts/create_testsuite_files: Add testsuite/experimental in
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@ -420,7 +420,7 @@
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the hash code every time it's needed can improve performance, but the
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additional memory overhead can also reduce performance, so whether an
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unordered associative container caches the hash code or not depends on
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a number of factors. The caching policy for GCC 4.8 is described below.
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the properties described below.
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</para>
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<para>
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The C++ standard requires that <code>erase</code> and <code>swap</code>
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@ -432,23 +432,8 @@
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or <code>throw()</code>.
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</para>
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<para>
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Secondly, libstdc++ also needs the hash code in the implementation of
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<code>local_iterator</code> and <code>const_local_iterator</code> in
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order to know when the iterator has reached the end of the bucket.
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This means that the local iterator types will embed a copy of the hash
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function when possible.
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Because the local iterator types must be DefaultConstructible and
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CopyAssignable, if the hash function type does not model those concepts
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then it cannot be embedded and so the hash code must be cached.
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Note that a hash function might not be safe to use when
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default-constructed (e.g if it a function pointer) so a hash
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function that is contained in a local iterator won't be used until
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the iterator is valid, so the hash function has been copied from a
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correctly-initialized object.
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</para>
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<para>
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If the hash function is non-throwing, DefaultConstructible and
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CopyAssignable then libstdc++ doesn't need to cache the hash code for
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If the hash function is non-throwing then libstdc++ doesn't need to
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cache the hash code for
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correctness, but might still do so for performance if computing a
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hash code is an expensive operation, as it may be for arbitrarily
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long strings.
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@ -42,10 +42,6 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
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using __cache_default
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= __not_<__and_<// Do not cache for fast hasher.
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__is_fast_hash<_Hash>,
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// Mandatory to make local_iterator default
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// constructible and assignable.
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is_default_constructible<_Hash>,
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is_copy_assignable<_Hash>,
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// Mandatory to have erase not throwing.
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__detail::__is_noexcept_hash<_Tp, _Hash>>>;
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@ -282,22 +278,6 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
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"Functor used to map hash code to bucket index"
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" must be default constructible");
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// When hash codes are not cached local iterator inherits from
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// __hash_code_base above to compute node bucket index so it has to be
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// default constructible.
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static_assert(__if_hash_not_cached<
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is_default_constructible<__hash_code_base_access>>::value,
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"Cache the hash code or make functors involved in hash code"
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" and bucket index computation default constructible");
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// When hash codes are not cached local iterator inherits from
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// __hash_code_base above to compute node bucket index so it has to be
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// assignable.
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static_assert(__if_hash_not_cached<
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is_copy_assignable<__hash_code_base>>::value,
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"Cache the hash code or make functors involved in hash code"
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" and bucket index computation copy assignable");
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template<typename _Keya, typename _Valuea, typename _Alloca,
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typename _ExtractKeya, typename _Equala,
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typename _H1a, typename _H2a, typename _Hasha,
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@ -19,7 +19,7 @@
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// with this library; see the file COPYING3. If not see
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// <http://www.gnu.org/licenses/>.
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// { dg-error "with noexcept" "" { target *-*-* } 270 }
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// { dg-error "with noexcept" "" { target *-*-* } 266 }
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#include <unordered_set>
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@ -1,51 +0,0 @@
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// { dg-do compile }
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// { dg-options "-std=c++11" }
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// { dg-require-normal-mode "" }
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// Copyright (C) 2013-2014 Free Software Foundation, Inc.
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//
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// This file is part of the GNU ISO C++ Library. This library is free
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// software; you can redistribute it and/or modify it under the
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// terms of the GNU General Public License as published by the
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// Free Software Foundation; either version 3, or (at your option)
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// any later version.
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// This library 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 along
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// with this library; see the file COPYING3. If not see
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// <http://www.gnu.org/licenses/>.
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// { dg-error "default constructible" "" { target *-*-* } 288 }
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#include <unordered_set>
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namespace
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{
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struct hash
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{
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hash(std::size_t seed)
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: _M_seed(seed)
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{ }
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std::size_t operator() (int val) const noexcept
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{ return val ^ _M_seed; }
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private:
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std::size_t _M_seed;
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};
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}
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void
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test01()
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{
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using traits = std::__detail::_Hashtable_traits<false, true, true>;
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using hashtable = std::__uset_hashtable<int, hash,
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std::equal_to<int>,
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std::allocator<int>, traits>;
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hashtable ht(10, hash(1));
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}
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