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epilkepilk
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Fix a strict aliasing violation in map and unordered_map.
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 llvm-svn: 333948
1 parent ba81d7f commit f52318b

4 files changed

Lines changed: 177 additions & 89 deletions

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‎libcxx/include/__hash_table‎

Lines changed: 5 additions & 11 deletions
Original file line numberDiff line numberDiff line change
@@ -32,13 +32,8 @@ _LIBCPP_PUSH_MACROS
3232

3333
_LIBCPP_BEGIN_NAMESPACE_STD
3434

35-
#ifndef _LIBCPP_CXX03_LANG
36-
template <class _Key, class _Tp>
37-
union __hash_value_type;
38-
#else
3935
template <class _Key, class _Tp>
4036
struct __hash_value_type;
41-
#endif
4237

4338
template <class _Key, class _Cp, class _Hash,
4439
bool = is_empty<_Hash>::value && !__libcpp_is_final<_Hash>::value>
@@ -172,7 +167,7 @@ struct __hash_key_value_types {
172167
}
173168
#ifndef _LIBCPP_CXX03_LANG
174169
_LIBCPP_INLINE_VISIBILITY
175-
static __container_value_type&& __move(__node_value_type& __v) {
170+
static __container_value_type&& __move(__node_value_type& __v) {
176171
return _VSTD::move(__v);
177172
}
178173
#endif
@@ -184,7 +179,6 @@ struct __hash_key_value_types<__hash_value_type<_Key, _Tp> > {
184179
typedef _Tp mapped_type;
185180
typedef __hash_value_type<_Key, _Tp> __node_value_type;
186181
typedef pair<const _Key, _Tp> __container_value_type;
187-
typedef pair<_Key, _Tp> __nc_value_type;
188182
typedef __container_value_type __map_value_type;
189183
static const bool __is_map = true;
190184

@@ -198,7 +192,7 @@ struct __hash_key_value_types<__hash_value_type<_Key, _Tp> > {
198192
static typename enable_if<__is_same_uncvref<_Up, __node_value_type>::value,
199193
__container_value_type const&>::type
200194
__get_value(_Up& __t) {
201-
return __t.__cc;
195+
return __t.__get_value();
202196
}
203197

204198
template <class _Up>
@@ -211,12 +205,12 @@ struct __hash_key_value_types<__hash_value_type<_Key, _Tp> > {
211205

212206
_LIBCPP_INLINE_VISIBILITY
213207
static __container_value_type* __get_ptr(__node_value_type& __n) {
214-
return _VSTD::addressof(__n.__cc);
208+
return _VSTD::addressof(__n.__get_value());
215209
}
216210
#ifndef _LIBCPP_CXX03_LANG
217211
_LIBCPP_INLINE_VISIBILITY
218-
static __nc_value_type&& __move(__node_value_type& __v) {
219-
return _VSTD::move(__v.__nc);
212+
static pair<key_type&&, mapped_type&&> __move(__node_value_type& __v) {
213+
return __v.__move();
220214
}
221215
#endif
222216

‎libcxx/include/__tree‎

Lines changed: 6 additions & 13 deletions
Original file line numberDiff line numberDiff line change
@@ -37,13 +37,8 @@ template <class _Pointer> class __tree_end_node;
3737
template <class _VoidPtr> class __tree_node_base;
3838
template <class _Tp, class _VoidPtr> class __tree_node;
3939

40-
#ifndef _LIBCPP_CXX03_LANG
41-
template <class _Key, class _Value>
42-
union __value_type;
43-
#else
4440
template <class _Key, class _Value>
4541
struct __value_type;
46-
#endif
4742

4843
template <class _Key, class _CP, class _Compare,
4944
bool = is_empty<_Compare>::value && !__libcpp_is_final<_Compare>::value>
@@ -569,10 +564,9 @@ struct __tree_key_value_types {
569564
static __container_value_type* __get_ptr(__node_value_type& __n) {
570565
return _VSTD::addressof(__n);
571566
}
572-
573567
#ifndef _LIBCPP_CXX03_LANG
574568
_LIBCPP_INLINE_VISIBILITY
575-
static __container_value_type&& __move(__node_value_type& __v) {
569+
static __container_value_type&& __move(__node_value_type& __v) {
576570
return _VSTD::move(__v);
577571
}
578572
#endif
@@ -584,14 +578,13 @@ struct __tree_key_value_types<__value_type<_Key, _Tp> > {
584578
typedef _Tp mapped_type;
585579
typedef __value_type<_Key, _Tp> __node_value_type;
586580
typedef pair<const _Key, _Tp> __container_value_type;
587-
typedef pair<_Key, _Tp> __nc_value_type;
588581
typedef __container_value_type __map_value_type;
589582
static const bool __is_map = true;
590583

591584
_LIBCPP_INLINE_VISIBILITY
592585
static key_type const&
593586
__get_key(__node_value_type const& __t) {
594-
return __t.__cc.first;
587+
return __t.__get_value().first;
595588
}
596589

597590
template <class _Up>
@@ -605,7 +598,7 @@ struct __tree_key_value_types<__value_type<_Key, _Tp> > {
605598
_LIBCPP_INLINE_VISIBILITY
606599
static __container_value_type const&
607600
__get_value(__node_value_type const& __t) {
608-
return __t.__cc;
601+
return __t.__get_value();
609602
}
610603

611604
template <class _Up>
@@ -618,13 +611,13 @@ struct __tree_key_value_types<__value_type<_Key, _Tp> > {
618611

619612
_LIBCPP_INLINE_VISIBILITY
620613
static __container_value_type* __get_ptr(__node_value_type& __n) {
621-
return _VSTD::addressof(__n.__cc);
614+
return _VSTD::addressof(__n.__get_value());
622615
}
623616

624617
#ifndef _LIBCPP_CXX03_LANG
625618
_LIBCPP_INLINE_VISIBILITY
626-
static __nc_value_type&& __move(__node_value_type& __v) {
627-
return _VSTD::move(__v.__nc);
619+
static pair<key_type&&, mapped_type&&> __move(__node_value_type& __v) {
620+
return __v.__move();
628621
}
629622
#endif
630623
};

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