From 5c86e63cb0383a38ec3dea24e9b3fe2f6e312057 Mon Sep 17 00:00:00 2001 From: Jonathan Wakely Date: Tue, 20 Jul 2021 15:20:41 +0100 Subject: [PATCH] libstdc++: fix is_default_constructible for hash containers [PR 100863] The recent change to _Hashtable_ebo_helper for this PR broke the is_default_constructible trait for a hash container with a non-default constructible allocator. That happens because the constructor needs to be user-provided in order to initialize the member, and so is not defined as deleted when the type is not default constructible. By making _Hashtable derive from _Enable_special_members we can ensure that the default constructor for the std::unordered_xxx containers is deleted when it would be ill-formed. This makes the trait give the correct answer. This backport to gcc-10 includes the fix for PR 101583. Signed-off-by: Jonathan Wakely libstdc++-v3/ChangeLog: PR libstdc++/100863 * include/bits/hashtable.h (_Hashtable): Conditionally delete default constructor by deriving from _Enable_default_constructor. Construct that base-class explicitly in all non-forwarding, non-defaulted constructors. * testsuite/23_containers/unordered_map/cons/default.cc: New test. * testsuite/23_containers/unordered_set/cons/default.cc: New test. (cherry picked from commit 89ec3b67dbe856a447d068b053bc19559f136f43) --- libstdc++-v3/include/bits/hashtable.h | 26 ++++++++-- .../unordered_map/cons/default.cc | 48 +++++++++++++++++++ .../unordered_set/cons/default.cc | 47 ++++++++++++++++++ 3 files changed, 118 insertions(+), 3 deletions(-) create mode 100644 libstdc++-v3/testsuite/23_containers/unordered_map/cons/default.cc create mode 100644 libstdc++-v3/testsuite/23_containers/unordered_set/cons/default.cc diff --git a/libstdc++-v3/include/bits/hashtable.h b/libstdc++-v3/include/bits/hashtable.h index 310eb52dd516..961e83049a58 100644 --- a/libstdc++-v3/include/bits/hashtable.h +++ b/libstdc++-v3/include/bits/hashtable.h @@ -33,6 +33,7 @@ #pragma GCC system_header #include +#include #if __cplusplus > 201402L # include #endif @@ -48,6 +49,16 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION // Mandatory to have erase not throwing. __is_nothrow_invocable>>; + // Helper to conditionally delete the default constructor. + // The _Hash_node_base type is used to distinguish this specialization + // from any other potentially-overlapping subobjects of the hashtable. + template + using _Hashtable_enable_default_ctor + = _Enable_default_constructor<__and_, + is_default_constructible<_Hash>, + is_default_constructible<_Allocator>>{}, + __detail::_Hash_node_base>; + /** * Primary class template _Hashtable. * @@ -184,7 +195,8 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION private __detail::_Hashtable_alloc< __alloc_rebind<_Alloc, __detail::_Hash_node<_Value, - _Traits::__hash_cached::value>>> + _Traits::__hash_cached::value>>>, + private _Hashtable_enable_default_ctor<_Equal, _H1, _Alloc> { static_assert(is_same::type, _Value>::value, "unordered container must have a non-const, non-volatile value_type"); @@ -206,6 +218,8 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION typename __hashtable_alloc::__node_alloc_traits; using __node_base = typename __hashtable_alloc::__node_base; using __bucket_type = typename __hashtable_alloc::__bucket_type; + using __enable_default_ctor + = _Hashtable_enable_default_ctor<_Equal, _H1, _Alloc>; public: typedef _Key key_type; @@ -443,7 +457,8 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION const _Equal& __eq, const _ExtractKey& __exk, const allocator_type& __a) : __hashtable_base(__exk, __h1, __h2, __h, __eq), - __hashtable_alloc(__node_alloc_type(__a)) + __hashtable_alloc(__node_alloc_type(__a)), + __enable_default_ctor(_Enable_default_constructor_tag{}) { } template @@ -504,7 +519,8 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION // Use delegating constructors. explicit _Hashtable(const allocator_type& __a) - : __hashtable_alloc(__node_alloc_type(__a)) + : __hashtable_alloc(__node_alloc_type(__a)), + __enable_default_ctor(_Enable_default_constructor_tag{}) { } explicit @@ -1302,6 +1318,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION __rehash_base(__ht), __hashtable_alloc( __node_alloc_traits::_S_select_on_copy(__ht._M_node_allocator())), + __enable_default_ctor(__ht), _M_buckets(nullptr), _M_bucket_count(__ht._M_bucket_count), _M_element_count(__ht._M_element_count), @@ -1324,6 +1341,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION __map_base(__ht), __rehash_base(__ht), __hashtable_alloc(std::move(__a)), + __enable_default_ctor(__ht), _M_buckets(__ht._M_buckets), _M_bucket_count(__ht._M_bucket_count), _M_before_begin(__ht._M_before_begin._M_nxt), @@ -1356,6 +1374,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION __map_base(__ht), __rehash_base(__ht), __hashtable_alloc(__node_alloc_type(__a)), + __enable_default_ctor(__ht), _M_buckets(), _M_bucket_count(__ht._M_bucket_count), _M_element_count(__ht._M_element_count), @@ -1377,6 +1396,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION __map_base(__ht), __rehash_base(__ht), __hashtable_alloc(std::move(__a)), + __enable_default_ctor(__ht), _M_buckets(nullptr), _M_bucket_count(__ht._M_bucket_count), _M_element_count(__ht._M_element_count), diff --git a/libstdc++-v3/testsuite/23_containers/unordered_map/cons/default.cc b/libstdc++-v3/testsuite/23_containers/unordered_map/cons/default.cc new file mode 100644 index 000000000000..d64d078a7dab --- /dev/null +++ b/libstdc++-v3/testsuite/23_containers/unordered_map/cons/default.cc @@ -0,0 +1,48 @@ +// { dg-do compile { target c++11 } } +#include + +static_assert( std::is_default_constructible>{}, "" ); + +template + struct NoDefaultConsAlloc + { + using value_type = T; + + NoDefaultConsAlloc(int) noexcept { } + + template + NoDefaultConsAlloc(const NoDefaultConsAlloc&) { } + + T *allocate(std::size_t n) + { return std::allocator().allocate(n); } + + void deallocate(T *p, std::size_t n) + { std::allocator().deallocate(p, n); } + }; + +using Map = std::unordered_map, std::equal_to, + NoDefaultConsAlloc>>; +static_assert( ! std::is_default_constructible{}, "PR libstdc++/100863" ); + +struct Hash : std::hash { Hash(int) { } }; +using Map2 = std::unordered_map; +static_assert( ! std::is_default_constructible{}, "PR libstdc++/100863" ); + +struct Equal : std::equal_to { Equal(int) { } }; +using Map3 = std::unordered_map, Equal>; +static_assert( ! std::is_default_constructible{}, "PR libstdc++/100863" ); + +// PR libstdc++/101583 +// verify non-default ctors can still be used +using Map4 = std::unordered_map>>; +Hash h(1); +Equal eq(1); +Map4::allocator_type a(1); +Map4 m{1, h, eq, a}; +Map4 m2{m.begin(), m.end(), m.size(), h, eq, a}; +Map4 m3{{{1,1}, {2,2}, {3,3}}, 3, h, eq, a}; +Map4 m4{m}; +Map4 m5{m, a}; +Map4 m6{std::move(m)}; +Map4 m7{std::move(m6), a}; diff --git a/libstdc++-v3/testsuite/23_containers/unordered_set/cons/default.cc b/libstdc++-v3/testsuite/23_containers/unordered_set/cons/default.cc new file mode 100644 index 000000000000..41281d3d774e --- /dev/null +++ b/libstdc++-v3/testsuite/23_containers/unordered_set/cons/default.cc @@ -0,0 +1,47 @@ +// { dg-do compile { target c++11 } } +#include + +static_assert( std::is_default_constructible>{}, "" ); + +template + struct NoDefaultConsAlloc + { + using value_type = T; + + NoDefaultConsAlloc(int) noexcept { } + + template + NoDefaultConsAlloc(const NoDefaultConsAlloc&) { } + + T *allocate(std::size_t n) + { return std::allocator().allocate(n); } + + void deallocate(T *p, std::size_t n) + { std::allocator().deallocate(p, n); } + }; + +using Set = std::unordered_set, std::equal_to, + NoDefaultConsAlloc>; +static_assert( ! std::is_default_constructible{}, "PR libstdc++/100863" ); + +struct Hash : std::hash { Hash(int) { } }; +using Set2 = std::unordered_set; +static_assert( ! std::is_default_constructible{}, "PR libstdc++/100863" ); + +struct Equal : std::equal_to { Equal(int) { } }; +using Set3 = std::unordered_set, Equal>; +static_assert( ! std::is_default_constructible{}, "PR libstdc++/100863" ); + +// PR libstdc++/101583 +// verify non-default ctors can still be used +using Set4 = std::unordered_set>; +Hash h(1); +Equal eq(1); +Set4::allocator_type a(1); +Set4 s{1, h, eq, a}; +Set4 s2{s.begin(), s.end(), s.size(), h, eq, a}; +Set4 s3{{1, 2, 3}, 3, h, eq, a}; +Set4 s4{s}; +Set4 s5{s, a}; +Set4 s6{std::move(s)}; +Set4 s7{std::move(s6), a}; -- 2.47.2