[committed] libstdc++: Fix non-default constructors for hash containers [PR101583]

Message ID YPm75Yxooq7q75bs@redhat.com
State New
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  • [committed] libstdc++: Fix non-default constructors for hash containers [PR101583]
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Commit Message

Martin Sebor via Gcc-patches July 22, 2021, 6:41 p.m.
On 20/07/21 16:26 +0100, Jonathan Wakely wrote:
>On 02/06/21 13:35 +0100, Jonathan Wakely wrote:

>>The allocator, hash function and equality function should all be

>>value-initialized by the default constructor of an unordered container.

>>Do it in the EBO helper, so we don't have to get it right in multiple

>>places.

>>

>>Signed-off-by: Jonathan Wakely <jwakely@redhat.com>

>>

>>libstdc++-v3/ChangeLog:

>>

>>	PR libstdc++/100863

>>	PR libstdc++/65816

>>	* include/bits/hashtable_policy.h (_Hashtable_ebo_helper):

>>	Value-initialize subobject.

>>	* testsuite/23_containers/unordered_map/allocator/default_init.cc:

>>	Remove XFAIL.

>>	* testsuite/23_containers/unordered_set/allocator/default_init.cc:

>>	Remove XFAIL.

>

>

>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.

>

>Signed-off-by: Jonathan Wakely <jwakely@redhat.com>

>

>libstdc++-v3/ChangeLog:

>

>        PR libstdc++/100863

>        * include/bits/hashtable.h (_Hashtable): Conditionally delete

>        default constructor by deriving from _Enable_special_members.

>        * testsuite/23_containers/unordered_map/cons/default.cc: New test.

>        * testsuite/23_containers/unordered_set/cons/default.cc: New test.

>


When I added the new mixin to _Hashtable, I forgot to explicitly
construct it in each non-default constructor. That means you can't
use any constructors unless all three of the hash function, equality
function, and allocator are all default constructible.

         PR libstdc++/101583
         * include/bits/hashtable.h (_Hashtable): Replace mixin with
         _Enable_default_ctor. Construct it explicitly in all
         non-forwarding, non-defaulted constructors.
         * testsuite/23_containers/unordered_map/cons/default.cc: Check
         non-default constructors can be used.
         * testsuite/23_containers/unordered_set/cons/default.cc:
         Likewise.

Tested powerpc64le-linux. Committed to trunk.

Patch

commit 8ed6cfbbee74ec9e03f2558b9c36f61dd7d4dcfd
Author: Jonathan Wakely <jwakely@redhat.com>
Date:   Thu Jul 22 18:49:57 2021

    libstdc++: Fix non-default constructors for hash containers [PR101583]
    
    When I added the new mixin to _Hashtable, I forgot to explicitly
    construct it in each non-default constructor. That means you can't
    use any constructors unless all three of the hash function, equality
    function, and allocator are all default constructible.
    
    libstdc++-v3/ChangeLog:
    
            PR libstdc++/101583
            * include/bits/hashtable.h (_Hashtable): Replace mixin with
            _Enable_default_ctor. Construct it explicitly in all
            non-forwarding, non-defaulted constructors.
            * testsuite/23_containers/unordered_map/cons/default.cc: Check
            non-default constructors can be used.
            * testsuite/23_containers/unordered_set/cons/default.cc:
            Likewise.

diff --git a/libstdc++-v3/include/bits/hashtable.h b/libstdc++-v3/include/bits/hashtable.h
index adb59213f2d..92516b81ae5 100644
--- a/libstdc++-v3/include/bits/hashtable.h
+++ b/libstdc++-v3/include/bits/hashtable.h
@@ -54,11 +54,10 @@  _GLIBCXX_BEGIN_NAMESPACE_VERSION
   // from any other potentially-overlapping subobjects of the hashtable.
   template<typename _Equal, typename _Hash, typename _Allocator>
     using _Hashtable_enable_default_ctor
-      = _Enable_special_members<__and_<is_default_constructible<_Equal>,
+      = _Enable_default_constructor<__and_<is_default_constructible<_Equal>,
 				       is_default_constructible<_Hash>,
 				       is_default_constructible<_Allocator>>{},
-				true, true, true, true, true,
-				__detail::_Hash_node_base>;
+				    __detail::_Hash_node_base>;
 
   /**
    *  Primary class template _Hashtable.
@@ -228,6 +227,8 @@  _GLIBCXX_BEGIN_NAMESPACE_VERSION
 					      _Equal, _Hash,
 					      _RangeHash, _Unused,
 					      _RehashPolicy, _Traits>;
+      using __enable_default_ctor
+	= _Hashtable_enable_default_ctor<_Equal, _Hash, _Alloc>;
 
     public:
       typedef _Key						key_type;
@@ -484,7 +485,8 @@  _GLIBCXX_BEGIN_NAMESPACE_VERSION
       _Hashtable(const _Hash& __h, const _Equal& __eq,
 		 const allocator_type& __a)
       : __hashtable_base(__h, __eq),
-	__hashtable_alloc(__node_alloc_type(__a))
+	__hashtable_alloc(__node_alloc_type(__a)),
+	__enable_default_ctor(_Enable_default_constructor_tag{})
       { }
 
       template<bool _No_realloc = true>
@@ -551,7 +553,8 @@  _GLIBCXX_BEGIN_NAMESPACE_VERSION
 
       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{})
       { }
 
       template<typename _InputIterator>
@@ -1435,6 +1438,7 @@  _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),
@@ -1457,6 +1461,7 @@  _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),
@@ -1487,6 +1492,7 @@  _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),
@@ -1508,6 +1514,7 @@  _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
index e4f836fde3e..d64d078a7da 100644
--- a/libstdc++-v3/testsuite/23_containers/unordered_map/cons/default.cc
+++ b/libstdc++-v3/testsuite/23_containers/unordered_map/cons/default.cc
@@ -31,3 +31,18 @@  static_assert( ! std::is_default_constructible<Map2>{}, "PR libstdc++/100863" );
 struct Equal : std::equal_to<int> { Equal(int) { } };
 using Map3 = std::unordered_map<int, int, std::hash<int>, Equal>;
 static_assert( ! std::is_default_constructible<Map3>{}, "PR libstdc++/100863" );
+
+// PR libstdc++/101583
+// verify non-default ctors can still be used
+using Map4 = std::unordered_map<int, int, Hash, Equal,
+			        NoDefaultConsAlloc<std::pair<const int, int>>>;
+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
index 42fbf3d7997..41281d3d774 100644
--- a/libstdc++-v3/testsuite/23_containers/unordered_set/cons/default.cc
+++ b/libstdc++-v3/testsuite/23_containers/unordered_set/cons/default.cc
@@ -31,3 +31,17 @@  static_assert( ! std::is_default_constructible<Set2>{}, "PR libstdc++/100863" );
 struct Equal : std::equal_to<int> { Equal(int) { } };
 using Set3 = std::unordered_set<int, std::hash<int>, Equal>;
 static_assert( ! std::is_default_constructible<Set3>{}, "PR libstdc++/100863" );
+
+// PR libstdc++/101583
+// verify non-default ctors can still be used
+using Set4 = std::unordered_set<int, Hash, Equal, NoDefaultConsAlloc<int>>;
+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};