https://gcc.gnu.org/g:b5d04ffcdf30076bf80aa48f7a67404c20597141
commit r14-11450-gb5d04ffcdf30076bf80aa48f7a67404c20597141
Author: Jonathan Wakely <jwak...@redhat.com>
Date: Tue Jul 16 09:43:06 2024 +0100
libstdc++: Define operator== for hash table iterators [PR115939]
Currently iterators for unordered containers do not directly define
operator== and operator!= overloads. Instead they rely on the base class
defining them, which is done so that iterator and const_iterator
comparisons work using the same overloads.
However this means a derived-to-base conversion is needed to call those
operators, and PR libstdc++/115939 shows that this can be ambiguous (for
-pedantic) when another overloaded operator could be used after an
implicit conversion.
This change defines operator== and operator!= directly for
_Node_iterator and _Node_const_iterator so that no derived-to-base
conversions are needed. The new overloads just forward to the base class
ones, so the implementation is still shared and doesn't need to be
duplicated.
libstdc++-v3/ChangeLog:
PR libstdc++/115939
* include/bits/hashtable_policy.h (_Node_iterator): Add
operator== and operator!=.
(_Node_const_iterator): Likewise.
* testsuite/23_containers/unordered_map/115939.cc: New test.
(cherry picked from commit 591b71993f15ed95eb38f3314f3d9ac159b9d051)
Diff:
---
libstdc++-v3/include/bits/hashtable_policy.h | 80 +++++++++++++++++++++-
.../23_containers/unordered_map/115939.cc | 29 ++++++++
2 files changed, 107 insertions(+), 2 deletions(-)
diff --git a/libstdc++-v3/include/bits/hashtable_policy.h
b/libstdc++-v3/include/bits/hashtable_policy.h
index 738a4da9382e..41a47b476127 100644
--- a/libstdc++-v3/include/bits/hashtable_policy.h
+++ b/libstdc++-v3/include/bits/hashtable_policy.h
@@ -464,6 +464,23 @@ namespace __detail
this->_M_incr();
return __tmp;
}
+
+#if __cpp_impl_three_way_comparison >= 201907L
+ friend bool
+ operator==(const _Node_iterator&, const _Node_iterator&) = default;
+#else
+ friend bool
+ operator==(const _Node_iterator& __x, const _Node_iterator& __y) noexcept
+ {
+ const __base_type& __bx = __x;
+ const __base_type& __by = __y;
+ return __bx == __by;
+ }
+
+ friend bool
+ operator!=(const _Node_iterator& __x, const _Node_iterator& __y) noexcept
+ { return !(__x == __y); }
+#endif
};
/// Node const_iterators, used to iterate through all the hashtable.
@@ -475,6 +492,10 @@ namespace __detail
using __base_type = _Node_iterator_base<_Value, __cache>;
using __node_type = typename __base_type::__node_type;
+ // The corresponding non-const iterator.
+ using __iterator
+ = _Node_iterator<_Value, __constant_iterators, __cache>;
+
public:
typedef _Value value_type;
typedef std::ptrdiff_t difference_type;
@@ -489,8 +510,7 @@ namespace __detail
_Node_const_iterator(__node_type* __p) noexcept
: __base_type(__p) { }
- _Node_const_iterator(const _Node_iterator<_Value, __constant_iterators,
- __cache>& __x) noexcept
+ _Node_const_iterator(const __iterator& __x) noexcept
: __base_type(__x._M_cur) { }
reference
@@ -515,6 +535,62 @@ namespace __detail
this->_M_incr();
return __tmp;
}
+
+#if __cpp_impl_three_way_comparison >= 201907L
+ friend bool
+ operator==(const _Node_const_iterator&,
+ const _Node_const_iterator&) = default;
+
+ friend bool
+ operator==(const _Node_const_iterator& __x, const __iterator& __y)
+ {
+ const __base_type& __bx = __x;
+ const __base_type& __by = __y;
+ return __bx == __by;
+ }
+#else
+ friend bool
+ operator==(const _Node_const_iterator& __x,
+ const _Node_const_iterator& __y) noexcept
+ {
+ const __base_type& __bx = __x;
+ const __base_type& __by = __y;
+ return __bx == __by;
+ }
+
+ friend bool
+ operator!=(const _Node_const_iterator& __x,
+ const _Node_const_iterator& __y) noexcept
+ { return !(__x == __y); }
+
+ friend bool
+ operator==(const _Node_const_iterator& __x,
+ const __iterator& __y) noexcept
+ {
+ const __base_type& __bx = __x;
+ const __base_type& __by = __y;
+ return __bx == __by;
+ }
+
+ friend bool
+ operator!=(const _Node_const_iterator& __x,
+ const __iterator& __y) noexcept
+ { return !(__x == __y); }
+
+ friend bool
+ operator==(const __iterator& __x,
+ const _Node_const_iterator& __y) noexcept
+ {
+ const __base_type& __bx = __x;
+ const __base_type& __by = __y;
+ return __bx == __by;
+ }
+
+ friend bool
+ operator!=(const __iterator& __x,
+ const _Node_const_iterator& __y) noexcept
+ { return !(__x == __y); }
+#endif
};
// Many of class template _Hashtable's template parameters are policy
diff --git a/libstdc++-v3/testsuite/23_containers/unordered_map/115939.cc
b/libstdc++-v3/testsuite/23_containers/unordered_map/115939.cc
new file mode 100644
index 000000000000..3a68acaff77f
--- /dev/null
+++ b/libstdc++-v3/testsuite/23_containers/unordered_map/115939.cc
@@ -0,0 +1,29 @@
+// { dg-options "-pedantic" }
+// { dg-do compile { target c++11 } }
+
+// Bug 115939 - Cannot unambiguously compare iterators in std::unordered_map
+
+#include <unordered_map>
+
+struct any_conv
+{
+ template<typename T>
+ any_conv(T&&) { }
+
+ template<typename T>
+ friend bool operator==(const any_conv&, const T&) { return true; }
+
+ template<typename T>
+ friend bool operator!=(const any_conv&, const T&) { return false; }
+};
+
+std::unordered_map<int, any_conv>::iterator i{};
+std::unordered_map<int, any_conv>::const_iterator j{};
+bool b1 = i == i; // { dg-bogus "ambiguous" }
+bool b2 = j == j; // { dg-bogus "ambiguous" }
+bool b3 = i == j; // { dg-bogus "ambiguous" }
+bool b4 = j == i; // { dg-bogus "ambiguous" }
+bool b5 = i != i; // { dg-bogus "ambiguous" }
+bool b6 = j != j; // { dg-bogus "ambiguous" }
+bool b7 = i != j; // { dg-bogus "ambiguous" }
+bool b8 = j != i; // { dg-bogus "ambiguous" }
