<deque>: Use _Next_iter and _Prev_iter (#1161)

microsoft · Aug 12, 2020 · ae1068e · ae1068e
1 parent 7f29487
commit ae1068e
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Showing 2 changed files with 24 additions and 7 deletions.
diff --git a/stl/inc/deque b/stl/inc/deque
@@ -836,10 +836,10 @@ public:
 
         if (_Off <= _Mysize() / 2) { // closer to front, push to front then rotate
             emplace_front(_STD forward<_Valty>(_Val)...);
-            _STD rotate(begin(), begin() + 1, begin() + static_cast<difference_type>(1 + _Off));
+            _STD rotate(begin(), _Next_iter(begin()), begin() + static_cast<difference_type>(1 + _Off));
         } else { // closer to back, push to back then rotate
             emplace_back(_STD forward<_Valty>(_Val)...);
-            _STD rotate(begin() + static_cast<difference_type>(_Off), end() - 1, end());
+            _STD rotate(begin() + static_cast<difference_type>(_Off), _Prev_iter(end()), end());
         }
         return begin() + static_cast<difference_type>(_Off);
     }
@@ -1064,15 +1064,15 @@ public:
         _STL_VERIFY(!empty(), "back() called on empty deque");
 #endif // _CONTAINER_DEBUG_LEVEL > 0
 
-        return *(_Unchecked_end() - 1);
+        return *_Prev_iter(_Unchecked_end());
     }
 
     _NODISCARD const_reference back() const noexcept /* strengthened */ {
 #if _CONTAINER_DEBUG_LEVEL > 0
         _STL_VERIFY(!empty(), "back() called on empty deque");
 #endif // _CONTAINER_DEBUG_LEVEL > 0
 
-        return *(_Unchecked_end() - 1);
+        return *_Prev_iter(_Unchecked_end());
     }
 
     void push_front(const _Ty& _Val) {
@@ -1197,10 +1197,10 @@ public:
 
         if (_Off <= _Mysize() / 2) { // closer to front, push to front then copy
             push_front(_Val);
-            _STD rotate(begin(), begin() + 1, begin() + static_cast<difference_type>(1 + _Off));
+            _STD rotate(begin(), _Next_iter(begin()), begin() + static_cast<difference_type>(1 + _Off));
         } else { // closer to back, push to back then copy
             push_back(_Val);
-            _STD rotate(begin() + static_cast<difference_type>(_Off), end() - 1, end());
+            _STD rotate(begin() + static_cast<difference_type>(_Off), _Prev_iter(end()), end());
         }
 
         return begin() + static_cast<difference_type>(_Off);

diff --git a/tests/std/tests/Dev10_500860_overloaded_address_of/test.cpp b/tests/std/tests/Dev10_500860_overloaded_address_of/test.cpp
@@ -282,7 +282,7 @@ constexpr bool can_addressof = false;
 template <typename T>
 constexpr bool can_addressof<T, void_t<decltype(addressof(declval<T>()))>> = true;
 
-void test_LWG_2598() {
+void test_LWG_2598() { // COMPILE-ONLY
     STATIC_ASSERT(can_addressof<int&>);
     STATIC_ASSERT(can_addressof<const int&>);
     STATIC_ASSERT(can_addressof<volatile int&>);
@@ -292,3 +292,20 @@ void test_LWG_2598() {
     STATIC_ASSERT(!can_addressof<volatile int>);
     STATIC_ASSERT(!can_addressof<const volatile int>);
 }
+
+// Also test DevCom-1134328, in which `deque<S*>::_Unchecked_iterator{} - 1` finds
+// operator-(const S&, int) by argument-dependent lookup causing overload resolution
+// to fail due to ambiguity when compiling 64-bit.
+struct S {
+    S() = default;
+
+    template <typename T>
+    S(T&&);
+};
+
+S operator-(const S&, int);
+
+void test_DevCom_1134328() { // COMPILE-ONLY
+    deque<S*> d{nullptr};
+    (void) d.back();
+}