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Fix a strict aliasing violation in map and unordered_map.

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These containers type-punned between pair<K, V> and pair<const K, V> as an
optimization. This commit instead provides access to the pair via a pair of
references that assign through to the underlying object. It's still undefined to
mutate a const object, but clang doesn't optimize on this for data members, so
this should be safe.

Differential revision: https://reviews.llvm.org/D47607

git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@333948 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Erik Pilkington
2018-06-04 20:38:23 +00:00
parent 8d476cd679
commit 55513c8efb
4 changed files with 177 additions and 89 deletions
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112
include/unordered_map
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@@ -396,7 +396,7 @@ public:
const _Hash& hash_function() const _NOEXCEPT {return *this;}
_LIBCPP_INLINE_VISIBILITY
size_t operator()(const _Cp& __x) const
{return static_cast<const _Hash&>(*this)(__x.__cc.first);}
{return static_cast<const _Hash&>(*this)(__x.__get_value().first);}
_LIBCPP_INLINE_VISIBILITY
size_t operator()(const _Key& __x) const
{return static_cast<const _Hash&>(*this)(__x);}
@@ -425,7 +425,7 @@ public:
const _Hash& hash_function() const _NOEXCEPT {return __hash_;}
_LIBCPP_INLINE_VISIBILITY
size_t operator()(const _Cp& __x) const
{return __hash_(__x.__cc.first);}
{return __hash_(__x.__get_value().first);}
_LIBCPP_INLINE_VISIBILITY
size_t operator()(const _Key& __x) const
{return __hash_(__x);}
@@ -464,13 +464,13 @@ public:
const _Pred& key_eq() const _NOEXCEPT {return *this;}
_LIBCPP_INLINE_VISIBILITY
bool operator()(const _Cp& __x, const _Cp& __y) const
{return static_cast<const _Pred&>(*this)(__x.__cc.first, __y.__cc.first);}
{return static_cast<const _Pred&>(*this)(__x.__get_value().first, __y.__get_value().first);}
_LIBCPP_INLINE_VISIBILITY
bool operator()(const _Cp& __x, const _Key& __y) const
{return static_cast<const _Pred&>(*this)(__x.__cc.first, __y);}
{return static_cast<const _Pred&>(*this)(__x.__get_value().first, __y);}
_LIBCPP_INLINE_VISIBILITY
bool operator()(const _Key& __x, const _Cp& __y) const
{return static_cast<const _Pred&>(*this)(__x, __y.__cc.first);}
{return static_cast<const _Pred&>(*this)(__x, __y.__get_value().first);}
void swap(__unordered_map_equal&__y)
_NOEXCEPT_(__is_nothrow_swappable<_Pred>::value)
{
@@ -496,13 +496,13 @@ public:
const _Pred& key_eq() const _NOEXCEPT {return __pred_;}
_LIBCPP_INLINE_VISIBILITY
bool operator()(const _Cp& __x, const _Cp& __y) const
{return __pred_(__x.__cc.first, __y.__cc.first);}
{return __pred_(__x.__get_value().first, __y.__get_value().first);}
_LIBCPP_INLINE_VISIBILITY
bool operator()(const _Cp& __x, const _Key& __y) const
{return __pred_(__x.__cc.first, __y);}
{return __pred_(__x.__get_value().first, __y);}
_LIBCPP_INLINE_VISIBILITY
bool operator()(const _Key& __x, const _Cp& __y) const
{return __pred_(__x, __y.__cc.first);}
{return __pred_(__x, __y.__get_value().first);}
void swap(__unordered_map_equal&__y)
_NOEXCEPT_(__is_nothrow_swappable<_Pred>::value)
{
@@ -572,9 +572,9 @@ public:
void operator()(pointer __p) _NOEXCEPT
{
if (__second_constructed)
__alloc_traits::destroy(__na_, _VSTD::addressof(__p->__value_.__cc.second));
__alloc_traits::destroy(__na_, _VSTD::addressof(__p->__value_.__get_value().second));
if (__first_constructed)
__alloc_traits::destroy(__na_, _VSTD::addressof(__p->__value_.__cc.first));
__alloc_traits::destroy(__na_, _VSTD::addressof(__p->__value_.__get_value().first));
if (__p)
__alloc_traits::deallocate(__na_, __p, 1);
}
@@ -582,23 +582,67 @@ public:
#ifndef _LIBCPP_CXX03_LANG
template <class _Key, class _Tp>
union __hash_value_type
struct __hash_value_type
{
typedef _Key key_type;
typedef _Tp mapped_type;
typedef pair<const key_type, mapped_type> value_type;
typedef pair<key_type, mapped_type> __nc_value_type;
typedef pair<key_type&, mapped_type&> __nc_ref_pair_type;
typedef pair<key_type&&, mapped_type&&> __nc_rref_pair_type;
private:
value_type __cc;
__nc_value_type __nc;
public:
_LIBCPP_INLINE_VISIBILITY
value_type& __get_value()
{
#if _LIBCPP_STD_VER > 14
return *_VSTD::launder(_VSTD::addressof(__cc));
#else
return __cc;
#endif
}
_LIBCPP_INLINE_VISIBILITY
const value_type& __get_value() const
{
#if _LIBCPP_STD_VER > 14
return *_VSTD::launder(_VSTD::addressof(__cc));
#else
return __cc;
#endif
}
_LIBCPP_INLINE_VISIBILITY
__nc_ref_pair_type __ref()
{
value_type& __v = __get_value();
return __nc_ref_pair_type(const_cast<key_type&>(__v.first), __v.second);
}
_LIBCPP_INLINE_VISIBILITY
__nc_rref_pair_type __move()
{
value_type& __v = __get_value();
return __nc_rref_pair_type(
_VSTD::move(const_cast<key_type&>(__v.first)),
_VSTD::move(__v.second));
}
_LIBCPP_INLINE_VISIBILITY
__hash_value_type& operator=(const __hash_value_type& __v)
{__nc = __v.__cc; return *this;}
{
__ref() = __v.__get_value();
return *this;
}
_LIBCPP_INLINE_VISIBILITY
__hash_value_type& operator=(__hash_value_type&& __v)
{__nc = _VSTD::move(__v.__nc); return *this;}
{
__ref() = __v.__move();
return *this;
}
template <class _ValueTp,
class = typename enable_if<
@@ -606,8 +650,10 @@ union __hash_value_type
>::type
>
_LIBCPP_INLINE_VISIBILITY
__hash_value_type& operator=(_ValueTp&& __v) {
__nc = _VSTD::forward<_ValueTp>(__v); return *this;
__hash_value_type& operator=(_ValueTp&& __v)
{
__ref() = _VSTD::forward<_ValueTp>(__v);
return *this;
}
private:
@@ -628,8 +674,15 @@ struct __hash_value_type
typedef _Tp mapped_type;
typedef pair<const key_type, mapped_type> value_type;
private:
value_type __cc;
public:
_LIBCPP_INLINE_VISIBILITY
value_type& __get_value() { return __cc; }
_LIBCPP_INLINE_VISIBILITY
const value_type& __get_value() const { return __cc; }
private:
~__hash_value_type();
};
@@ -657,9 +710,9 @@ public:
__hash_map_iterator(_HashIterator __i) _NOEXCEPT : __i_(__i) {}
_LIBCPP_INLINE_VISIBILITY
reference operator*() const {return __i_->__cc;}
reference operator*() const {return __i_->__get_value();}
_LIBCPP_INLINE_VISIBILITY
pointer operator->() const {return pointer_traits<pointer>::pointer_to(__i_->__cc);}
pointer operator->() const {return pointer_traits<pointer>::pointer_to(__i_->__get_value());}
_LIBCPP_INLINE_VISIBILITY
__hash_map_iterator& operator++() {++__i_; return *this;}
@@ -711,9 +764,9 @@ public:
: __i_(__i.__i_) {}
_LIBCPP_INLINE_VISIBILITY
reference operator*() const {return __i_->__cc;}
reference operator*() const {return __i_->__get_value();}
_LIBCPP_INLINE_VISIBILITY
pointer operator->() const {return pointer_traits<pointer>::pointer_to(__i_->__cc);}
pointer operator->() const {return pointer_traits<pointer>::pointer_to(__i_->__get_value());}
_LIBCPP_INLINE_VISIBILITY
__hash_map_const_iterator& operator++() {++__i_; return *this;}
@@ -750,7 +803,6 @@ public:
typedef _Pred key_equal;
typedef _Alloc allocator_type;
typedef pair<const key_type, mapped_type> value_type;
typedef pair<key_type, mapped_type> __nc_value_type;
typedef value_type& reference;
typedef const value_type& const_reference;
static_assert((is_same<value_type, typename allocator_type::value_type>::value),
@@ -1298,8 +1350,8 @@ unordered_map<_Key, _Tp, _Hash, _Pred, _Alloc>::unordered_map(
{
iterator __i = __u.begin();
while (__u.size() != 0) {
__table_.__emplace_unique(_VSTD::move(
__u.__table_.remove((__i++).__i_)->__value_.__nc));
__table_.__emplace_unique(
__u.__table_.remove((__i++).__i_)->__value_.__move());
}
}
#if _LIBCPP_DEBUG_LEVEL >= 2
@@ -1385,7 +1437,7 @@ unordered_map<_Key, _Tp, _Hash, _Pred, _Alloc>::operator[](const key_type& __k)
{
return __table_.__emplace_unique_key_args(__k,
std::piecewise_construct, std::forward_as_tuple(__k),
std::forward_as_tuple()).first->__cc.second;
std::forward_as_tuple()).first->__get_value().second;
}
template <class _Key, class _Tp, class _Hash, class _Pred, class _Alloc>
@@ -1394,7 +1446,7 @@ unordered_map<_Key, _Tp, _Hash, _Pred, _Alloc>::operator[](key_type&& __k)
{
return __table_.__emplace_unique_key_args(__k,
std::piecewise_construct, std::forward_as_tuple(std::move(__k)),
std::forward_as_tuple()).first->__cc.second;
std::forward_as_tuple()).first->__get_value().second;
}
#else // _LIBCPP_CXX03_LANG
@@ -1404,9 +1456,9 @@ unordered_map<_Key, _Tp, _Hash, _Pred, _Alloc>::__construct_node_with_key(const
{
__node_allocator& __na = __table_.__node_alloc();
__node_holder __h(__node_traits::allocate(__na, 1), _Dp(__na));
__node_traits::construct(__na, _VSTD::addressof(__h->__value_.__cc.first), __k);
__node_traits::construct(__na, _VSTD::addressof(__h->__value_.__get_value().first), __k);
__h.get_deleter().__first_constructed = true;
__node_traits::construct(__na, _VSTD::addressof(__h->__value_.__cc.second));
__node_traits::construct(__na, _VSTD::addressof(__h->__value_.__get_value().second));
__h.get_deleter().__second_constructed = true;
return _LIBCPP_EXPLICIT_MOVE(__h); // explicitly moved for C++03
}
@@ -1500,7 +1552,6 @@ public:
typedef _Pred key_equal;
typedef _Alloc allocator_type;
typedef pair<const key_type, mapped_type> value_type;
typedef pair<key_type, mapped_type> __nc_value_type;
typedef value_type& reference;
typedef const value_type& const_reference;
static_assert((is_same<value_type, typename allocator_type::value_type>::value),
@@ -1915,8 +1966,7 @@ unordered_multimap<_Key, _Tp, _Hash, _Pred, _Alloc>::unordered_multimap(
while (__u.size() != 0)
{
__table_.__insert_multi(
_VSTD::move(__u.__table_.remove((__i++).__i_)->__value_.__nc)
);
__u.__table_.remove((__i++).__i_)->__value_.__move());
}
}
#if _LIBCPP_DEBUG_LEVEL >= 2