libstdc++: [_Hashtable] Do not reuse untrusted cached hash code
On merge, reuse a merged node's possibly cached hash code only if we are on the same type of hash and this hash is stateless. Usage of function pointers or std::function as hash functor will prevent reusing cached hash code. libstdc++-v3/ChangeLog * include/bits/hashtable_policy.h (_Hash_code_base::_M_hash_code(const _Hash&, const _Hash_node_value<>&)): Remove. (_Hash_code_base::_M_hash_code<_H2>(const _H2&, const _Hash_node_value<>&)): Remove. * include/bits/hashtable.h (_M_src_hash_code<_H2>(const _H2&, const key_type&, const __node_value_type&)): New. (_M_merge_unique<>, _M_merge_multi<>): Use latter. * testsuite/23_containers/unordered_map/modifiers/merge.cc (test04, test05, test06): New test cases.
This commit is contained in:
François Dumont
parent
2454ba9e2d
commit
c714b4d30d
3 changed files with 190 additions and 20 deletions
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@ -1109,6 +1109,20 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
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return { __n, this->_M_node_allocator() };
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}
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// Only use the possibly cached node's hash code if its hash function
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// _H2 matches _Hash and is stateless. Otherwise recompute it using _Hash.
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template<typename _H2>
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__hash_code
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_M_src_hash_code(const _H2&, const key_type& __k,
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const __node_value_type& __src_n) const
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{
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if constexpr (std::is_same_v<_H2, _Hash>)
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if constexpr (std::is_empty_v<_Hash>)
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return this->_M_hash_code(__src_n);
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return this->_M_hash_code(__k);
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}
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public:
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// Extract a node.
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node_type
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@ -1146,7 +1160,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
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auto __pos = __i++;
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const key_type& __k = _ExtractKey{}(*__pos);
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__hash_code __code
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= this->_M_hash_code(__src.hash_function(), *__pos._M_cur);
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= _M_src_hash_code(__src.hash_function(), __k, *__pos._M_cur);
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size_type __bkt = _M_bucket_index(__code);
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if (_M_find_node(__bkt, __k, __code) == nullptr)
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{
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@ -1174,8 +1188,9 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
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for (auto __i = __src.cbegin(), __end = __src.cend(); __i != __end;)
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{
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auto __pos = __i++;
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const key_type& __k = _ExtractKey{}(*__pos);
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__hash_code __code
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= this->_M_hash_code(__src.hash_function(), *__pos._M_cur);
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= _M_src_hash_code(__src.hash_function(), __k, *__pos._M_cur);
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auto __nh = __src.extract(__pos);
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__hint = _M_insert_multi_node(__hint, __code, __nh._M_ptr)._M_cur;
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__nh._M_ptr = nullptr;
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@ -1319,19 +1319,6 @@ namespace __detail
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return _M_hash()(__k);
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}
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__hash_code
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_M_hash_code(const _Hash&,
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const _Hash_node_value<_Value, true>& __n) const
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{ return __n._M_hash_code; }
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// Compute hash code using _Hash as __n _M_hash_code, if present, was
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// computed using _H2.
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template<typename _H2>
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__hash_code
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_M_hash_code(const _H2&,
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const _Hash_node_value<_Value, __cache_hash_code>& __n) const
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{ return _M_hash_code(_ExtractKey{}(__n._M_v())); }
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__hash_code
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_M_hash_code(const _Hash_node_value<_Value, false>& __n) const
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{ return _M_hash_code(_ExtractKey{}(__n._M_v())); }
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@ -17,15 +17,29 @@
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// { dg-do run { target c++17 } }
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#include <string>
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#include <functional>
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#include <unordered_map>
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#include <algorithm>
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#include <testsuite_hooks.h>
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using test_type = std::unordered_map<int, int>;
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struct hash {
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auto operator()(int i) const noexcept { return ~std::hash<int>()(i); }
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};
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template<typename T>
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struct xhash
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{
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auto operator()(const T& i) const noexcept
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{ return ~std::hash<T>()(i); }
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};
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namespace std
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{
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template<typename T>
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struct __is_fast_hash<xhash<T>> : __is_fast_hash<std::hash<T>>
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{ };
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}
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struct equal : std::equal_to<> { };
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template<typename C1, typename C2>
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@ -64,7 +78,7 @@ test02()
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{
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const test_type c0{ {1, 10}, {2, 20}, {3, 30} };
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test_type c1 = c0;
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std::unordered_map<int, int, hash, equal> c2( c0.begin(), c0.end() );
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std::unordered_map<int, int, xhash<int>, equal> c2( c0.begin(), c0.end() );
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c1.merge(c2);
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VERIFY( c1 == c0 );
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@ -89,7 +103,7 @@ test03()
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{
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const test_type c0{ {1, 10}, {2, 20}, {3, 30} };
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test_type c1 = c0;
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std::unordered_multimap<int, int, hash, equal> c2( c0.begin(), c0.end() );
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std::unordered_multimap<int, int, xhash<int>, equal> c2( c0.begin(), c0.end() );
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c1.merge(c2);
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VERIFY( c1 == c0 );
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VERIFY( equal_elements(c2, c0) );
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@ -125,10 +139,164 @@ test03()
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VERIFY( c2.empty() );
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}
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void
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test04()
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{
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const std::unordered_map<std::string, int> c0
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{ {"one", 10}, {"two", 20}, {"three", 30} };
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std::unordered_map<std::string, int> c1 = c0;
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std::unordered_multimap<std::string, int> c2( c0.begin(), c0.end() );
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c1.merge(c2);
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VERIFY( c1 == c0 );
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VERIFY( equal_elements(c2, c0) );
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c1.clear();
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c1.merge(c2);
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VERIFY( c1 == c0 );
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VERIFY( c2.empty() );
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c2.merge(c1);
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VERIFY( c1.empty() );
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VERIFY( equal_elements(c2, c0) );
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c1 = c0;
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c2.merge(c1);
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VERIFY( c1.empty() );
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VERIFY( c2.size() == (2 * c0.size()) );
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VERIFY( c2.count("one") == 2 );
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VERIFY( c2.count("two") == 2 );
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VERIFY( c2.count("three") == 2 );
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c1.merge(c2);
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VERIFY( c1 == c0 );
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VERIFY( equal_elements(c2, c0) );
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c1.merge(std::move(c2));
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VERIFY( c1 == c0 );
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VERIFY( equal_elements(c2, c0) );
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c1.clear();
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c1.merge(std::move(c2));
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VERIFY( c1 == c0 );
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VERIFY( c2.empty() );
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}
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void
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test05()
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{
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const std::unordered_map<std::string, int> c0
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{ {"one", 10}, {"two", 20}, {"three", 30} };
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std::unordered_map<std::string, int> c1 = c0;
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std::unordered_multimap<std::string, int, xhash<std::string>, equal> c2( c0.begin(), c0.end() );
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c1.merge(c2);
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VERIFY( c1 == c0 );
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VERIFY( equal_elements(c2, c0) );
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c1.clear();
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c1.merge(c2);
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VERIFY( c1 == c0 );
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VERIFY( c2.empty() );
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c2.merge(c1);
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VERIFY( c1.empty() );
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VERIFY( equal_elements(c2, c0) );
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c1 = c0;
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c2.merge(c1);
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VERIFY( c1.empty() );
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VERIFY( c2.size() == (2 * c0.size()) );
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VERIFY( c2.count("one") == 2 );
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VERIFY( c2.count("two") == 2 );
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VERIFY( c2.count("three") == 2 );
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c1.merge(c2);
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VERIFY( c1 == c0 );
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VERIFY( equal_elements(c2, c0) );
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c1.merge(std::move(c2));
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VERIFY( c1 == c0 );
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VERIFY( equal_elements(c2, c0) );
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c1.clear();
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c1.merge(std::move(c2));
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VERIFY( c1 == c0 );
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VERIFY( c2.empty() );
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}
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template<typename T>
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using hash_f =
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std::function<std::size_t(const T&)>;
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std::size_t
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hash_func(const std::string& str)
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{ return std::hash<std::string>{}(str); }
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std::size_t
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xhash_func(const std::string& str)
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{ return xhash<std::string>{}(str); }
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namespace std
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{
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template<typename T>
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struct __is_fast_hash<hash_f<T>> : __is_fast_hash<std::hash<T>>
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{ };
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}
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void
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test06()
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{
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const std::unordered_map<std::string, int, hash_f<std::string>, equal>
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c0({ {"one", 10}, {"two", 20}, {"three", 30} }, 3, &hash_func);
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std::unordered_map<std::string, int, hash_f<std::string>, equal>
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c1(3, &hash_func);
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c1 = c0;
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std::unordered_multimap<std::string, int, hash_f<std::string>, equal>
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c2(c0.begin(), c0.end(), 3, &xhash_func);
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c1.merge(c2);
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VERIFY( c1 == c0 );
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VERIFY( equal_elements(c2, c0) );
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c1.clear();
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c1.merge(c2);
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VERIFY( c1 == c0 );
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VERIFY( c2.empty() );
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c2.merge(c1);
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VERIFY( c1.empty() );
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VERIFY( equal_elements(c2, c0) );
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c1 = c0;
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c2.merge(c1);
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VERIFY( c1.empty() );
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VERIFY( c2.size() == (2 * c0.size()) );
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VERIFY( c2.count("one") == 2 );
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VERIFY( c2.count("two") == 2 );
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VERIFY( c2.count("three") == 2 );
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c1.merge(c2);
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VERIFY( c1 == c0 );
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VERIFY( equal_elements(c2, c0) );
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c1.merge(std::move(c2));
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VERIFY( c1 == c0 );
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VERIFY( equal_elements(c2, c0) );
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c1.clear();
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c1.merge(std::move(c2));
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VERIFY( c1 == c0 );
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VERIFY( c2.empty() );
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}
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int
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main()
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{
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test01();
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test02();
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test03();
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test04();
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test05();
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test06();
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}
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