Add a comment explaining the extra comparison in raw_hash_set::operator==. Also add a small optimization to avoid the extra comparison in sets that use hash_default_eq as the key_equal functor.
Note that removing the comparison entirely causes the Table.Equality2 test case to fail.
PiperOrigin-RevId: 693447075
Change-Id: I769f75cf1cb27114455f1854e330c899cee55fc2
diff --git a/absl/container/flat_hash_set_test.cc b/absl/container/flat_hash_set_test.cc
index 96d7744..68ea7a0 100644
--- a/absl/container/flat_hash_set_test.cc
+++ b/absl/container/flat_hash_set_test.cc
@@ -17,6 +17,7 @@
#include <cstddef>
#include <cstdint>
#include <memory>
+#include <string>
#include <type_traits>
#include <utility>
#include <vector>
@@ -337,6 +338,19 @@
EXPECT_THAT(s1, UnorderedElementsAre(2));
}
+TEST(FlatHashSet, Equality) {
+ {
+ flat_hash_set<int> s1 = {1, 2, 3};
+ flat_hash_set<int> s2 = {1, 2, 3};
+ EXPECT_EQ(s1, s2);
+ }
+ {
+ flat_hash_set<std::string> s1 = {"a", "b", "c"};
+ flat_hash_set<std::string> s2 = {"a", "b", "c"};
+ EXPECT_EQ(s1, s2);
+ }
+}
+
} // namespace
} // namespace container_internal
ABSL_NAMESPACE_END
diff --git a/absl/container/internal/raw_hash_set.h b/absl/container/internal/raw_hash_set.h
index cc693f6..76e12d7 100644
--- a/absl/container/internal/raw_hash_set.h
+++ b/absl/container/internal/raw_hash_set.h
@@ -3471,7 +3471,16 @@
if (outer->capacity() > inner->capacity()) std::swap(outer, inner);
for (const value_type& elem : *outer) {
auto it = PolicyTraits::apply(FindElement{*inner}, elem);
- if (it == inner->end() || !(*it == elem)) return false;
+ if (it == inner->end()) return false;
+ // Note: we used key_equal to check for key equality in FindElement, but
+ // we may need to do an additional comparison using
+ // value_type::operator==. E.g. the keys could be equal and the
+ // mapped_types could be unequal in a map or even in a set, key_equal
+ // could ignore some fields that aren't ignored by operator==.
+ static constexpr bool kKeyEqIsValueEq =
+ std::is_same<key_type, value_type>::value &&
+ std::is_same<key_equal, hash_default_eq<key_type>>::value;
+ if (!kKeyEqIsValueEq && !(*it == elem)) return false;
}
return true;
}
