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Re: Value type of map need not be default copyable


On 08/08/2012 03:39 PM, Paolo Carlini wrote:
On 08/08/2012 03:15 PM, FranÃois Dumont wrote:
I have also introduce a special std::pair constructor for container usage so that we do not have to include the whole tuple stuff just for associative container implementations.
To be clear: sorry, this is not an option.

Paolo.

Then I can only imagine the attached patch which require to include tuple when including unordered_map or unordered_set. The std::pair(piecewise_construct_t, tuple<>, tuple<>) is the only constructor that allow to build a pair using the default constructor for the second member.

In fact, adding declaration for std::make_tuple and std::forward_as_tuple could avoid to include tuple from unordered_set, there is no operator[] on unordered_set or unordered_multiset. But I am not sure it worth the effort, tell me.

All unordered tests run under Linux x86_64, normal and debug modes.

2012-08-08  FranÃois Dumont  <fdumont@gcc.gnu.org>
        Ollie Wild  <aaw@google.com>

    * include/bits/hashtable.h (_Hashtable<>::_M_insert_bucket):
    Replace by ...
    (_Hashtable<>::_M_insert_node): ... this, new.
    (_Hashtable<>::_M_insert(_Args&&, true_type)): Use latter.
    * include/bits/hashtable_policy.h (_Map_base<>::operator[]): Use
    latter, emplace the value_type rather than insert.
    * include/std/unordered_map: Include tuple.
    * include/std/unordered_set: Likewise.
    * testsuite/23_containers/unordered_map/operators/2.cc: New.

FranÃois

Index: include/std/unordered_map
===================================================================
--- include/std/unordered_map	(revision 190209)
+++ include/std/unordered_map	(working copy)
@@ -38,6 +38,7 @@
 #include <utility>
 #include <type_traits>
 #include <initializer_list>
+#include <tuple>
 #include <bits/stl_algobase.h>
 #include <bits/allocator.h>
 #include <bits/stl_function.h> // equal_to, _Identity, _Select1st
Index: include/std/unordered_set
===================================================================
--- include/std/unordered_set	(revision 190209)
+++ include/std/unordered_set	(working copy)
@@ -38,6 +38,7 @@
 #include <utility>
 #include <type_traits>
 #include <initializer_list>
+#include <tuple>
 #include <bits/stl_algobase.h>
 #include <bits/allocator.h>
 #include <bits/stl_function.h> // equal_to, _Identity, _Select1st
Index: include/bits/hashtable.h
===================================================================
--- include/bits/hashtable.h	(revision 190209)
+++ include/bits/hashtable.h	(working copy)
@@ -584,11 +584,11 @@
       __node_base*
       _M_get_previous_node(size_type __bkt, __node_base* __n);
 
-      template<typename _Arg>
-	iterator
-	_M_insert_bucket(_Arg&&, size_type, __hash_code);
+      // Insert node in bucket bkt (assumes no element with its key already
+      // present). Take ownership of the node, deallocate it on exception.
+      iterator
+      _M_insert_node(size_type __bkt, __hash_code __code, __node_type* __n);
 
-
       template<typename... _Args>
 	std::pair<iterator, bool>
 	_M_emplace(std::true_type, _Args&&... __args);
@@ -1307,54 +1307,49 @@
 	  }
       }
 
-  // Insert v in bucket n (assumes no element with its key already present).
+  // Insert node in bucket bkt (assumes no element with its key already
+  // present). Take ownership of the node, deallocate it on exception.
   template<typename _Key, typename _Value,
 	   typename _Alloc, typename _ExtractKey, typename _Equal,
 	   typename _H1, typename _H2, typename _Hash, typename _RehashPolicy,
 	   typename _Traits>
-    template<typename _Arg>
-      typename _Hashtable<_Key, _Value, _Alloc, _ExtractKey, _Equal,
-			  _H1, _H2, _Hash, _RehashPolicy,
-			  _Traits>::iterator
-      _Hashtable<_Key, _Value, _Alloc, _ExtractKey, _Equal,
-		 _H1, _H2, _Hash, _RehashPolicy, _Traits>::
-      _M_insert_bucket(_Arg&& __v, size_type __n, __hash_code __code)
-      {
-	const __rehash_state& __saved_state = _M_rehash_policy._M_state();
-	std::pair<bool, std::size_t> __do_rehash
-	  = _M_rehash_policy._M_need_rehash(_M_bucket_count,
-					    _M_element_count, 1);
+    typename _Hashtable<_Key, _Value, _Alloc, _ExtractKey, _Equal,
+			_H1, _H2, _Hash, _RehashPolicy,
+			_Traits>::iterator
+    _Hashtable<_Key, _Value, _Alloc, _ExtractKey, _Equal,
+	       _H1, _H2, _Hash, _RehashPolicy, _Traits>::
+    _M_insert_node(size_type __bkt, __hash_code __code, __node_type* __node)
+    {
+      const __rehash_state& __saved_state = _M_rehash_policy._M_state();
+      std::pair<bool, std::size_t> __do_rehash
+	= _M_rehash_policy._M_need_rehash(_M_bucket_count,
+					  _M_element_count, 1);
 
-	if (__do_rehash.first)
-	  {
-	    const key_type& __k = this->_M_extract()(__v);
-	    __n = __hash_code_base::_M_bucket_index(__k, __code,
+      if (__do_rehash.first)
+	{
+	  const key_type& __k = this->_M_extract()(__node->_M_v);
+	  __bkt = __hash_code_base::_M_bucket_index(__k, __code,
 						    __do_rehash.second);
-	  }
+	}
 
-	__node_type* __node = nullptr;
-	__try
-	  {
-	    // Allocate the new node before doing the rehash so that we
-	    // don't do a rehash if the allocation throws.
-	    __node = _M_allocate_node(std::forward<_Arg>(__v));
-	    this->_M_store_code(__node, __code);
-	    if (__do_rehash.first)
-	      _M_rehash(__do_rehash.second, __saved_state);
+      __try
+	{
+	  if (__do_rehash.first)
+	    _M_rehash(__do_rehash.second, __saved_state);
 
-	    _M_insert_bucket_begin(__n, __node);
-	    ++_M_element_count;
-	    return iterator(__node);
-	  }
-	__catch(...)
-	  {
-	    if (!__node)
-	      _M_rehash_policy._M_reset(__saved_state);
-	    else
-	      _M_deallocate_node(__node);
-	    __throw_exception_again;
-	  }
-      }
+	  _M_insert_bucket_begin(__bkt, __node);
+	  ++_M_element_count;
+	  return iterator(__node);
+	}
+      __catch(...)
+	{
+	  if (!__node)
+	    _M_rehash_policy._M_reset(__saved_state);
+	  else
+	    _M_deallocate_node(__node);
+	  __throw_exception_again;
+	}
+    }
 
   // Insert v if no element with its key is already present.
   template<typename _Key, typename _Value,
@@ -1372,12 +1367,15 @@
       {
 	const key_type& __k = this->_M_extract()(__v);
 	__hash_code __code = this->_M_hash_code(__k);
-	size_type __n = _M_bucket_index(__k, __code);
+	size_type __bkt = _M_bucket_index(__k, __code);
 
-	if (__node_type* __p = _M_find_node(__n, __k, __code))
-	  return std::make_pair(iterator(__p), false);
-	return std::make_pair(_M_insert_bucket(std::forward<_Arg>(__v),
-			      __n, __code), true);
+	__node_type* __n = _M_find_node(__bkt, __k, __code);
+	if (__n)
+	  return std::make_pair(iterator(__n), false);
+
+	__n = _M_allocate_node(std::forward<_Arg>(__v));
+	this->_M_store_code(__n, __code);
+	return std::make_pair(_M_insert_node(__bkt, __code, __n), true);
       }
 
   // Insert v unconditionally.
@@ -1441,7 +1439,6 @@
 	  }
       }
 
-
   template<typename _Key, typename _Value,
 	   typename _Alloc, typename _ExtractKey, typename _Equal,
 	   typename _H1, typename _H2, typename _Hash, typename _RehashPolicy,
Index: include/bits/hashtable_policy.h
===================================================================
--- include/bits/hashtable_policy.h	(revision 190209)
+++ include/bits/hashtable_policy.h	(working copy)
@@ -577,8 +577,14 @@
       __node_type* __p = __h->_M_find_node(__n, __k, __code);
 
       if (!__p)
-	return __h->_M_insert_bucket(std::make_pair(__k, mapped_type()),
-				     __n, __code)->second;
+	{
+	  __p = __h->_M_allocate_node(std::piecewise_construct,
+				      std::make_tuple(__k),
+				      std::make_tuple());
+	  __h->_M_store_code(__p, __code);
+	  return __h->_M_insert_node(__n, __code, __p)->second;
+	}
+
       return (__p->_M_v).second;
     }
 
@@ -598,9 +604,14 @@
       __node_type* __p = __h->_M_find_node(__n, __k, __code);
 
       if (!__p)
-	return __h->_M_insert_bucket(std::make_pair(std::move(__k),
-						    mapped_type()),
-				     __n, __code)->second;
+	{
+	  __p = __h->_M_allocate_node(std::piecewise_construct,
+				std::forward_as_tuple(forward<key_type>(__k)),
+				std::make_tuple());
+	  __h->_M_store_code(__p, __code);
+	  return __h->_M_insert_node(__n, __code, __p)->second;
+	}
+
       return (__p->_M_v).second;
     }
 
Index: testsuite/23_containers/unordered_map/operators/2.cc
===================================================================
--- testsuite/23_containers/unordered_map/operators/2.cc	(revision 0)
+++ testsuite/23_containers/unordered_map/operators/2.cc	(revision 0)
@@ -0,0 +1,44 @@
+// Copyright (C) 2012 Free Software Foundation, Inc.
+//
+// This file is part of the GNU ISO C++ Library.  This library is free
+// software; you can redistribute it and/or modify it under the
+// terms of the GNU General Public License as published by the
+// Free Software Foundation; either version 3, or (at your option)
+// any later version.
+
+// This library is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+
+// You should have received a copy of the GNU General Public License along
+// with this library; see the file COPYING3.  If not see
+// <http://www.gnu.org/licenses/>.
+
+// 23.5.4 template class unordered_map
+
+// This test verifies that the value type of a unordered_map need not be
+// default copyable.
+
+// { dg-do compile }
+// { dg-options "-std=gnu++11" }
+
+#include <unordered_map>
+#include <testsuite_rvalref.h>
+
+struct Mapped
+{
+  Mapped() = default;
+  explicit Mapped(const Mapped&) = default;
+};
+
+void foo()
+{
+  using __gnu_test::rvalstruct;
+
+  std::unordered_map<int, Mapped> m1;
+  m1[0] = Mapped();
+
+  std::unordered_map<int, rvalstruct> m2;
+  m2[0] = rvalstruct(13);
+}

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