Add a flat_hash_set_test that we use value_type member functions to read/write from value_types when we aren't allowed to memcpy them.

The motivation is to prevent a bug in small buffer optimization for swisstables.

PiperOrigin-RevId: 564726325
Change-Id: Id0df5d28d65c7586428001fcb266886988cd481e

3 files changed, 69 insertions, 0 deletions

diff --git a/absl/container/BUILD.bazel b/absl/container/BUILD.bazel
index a1f6fd4f..208e78e8 100644
--- a/absl/container/BUILD.bazel
+++ b/absl/container/BUILD.bazel
@@ -283,12 +283,14 @@ cc_test(
     linkopts = ABSL_DEFAULT_LINKOPTS,
     tags = ["no_test_loonix"],
     deps = [
+        ":container_memory",
         ":flat_hash_set",
         ":hash_generator_testing",
         ":unordered_set_constructor_test",
         ":unordered_set_lookup_test",
         ":unordered_set_members_test",
         ":unordered_set_modifiers_test",
+        "//absl/base:config",
         "//absl/log:check",
         "//absl/memory",
         "//absl/strings",
diff --git a/absl/container/CMakeLists.txt b/absl/container/CMakeLists.txt
index f3443a66..64f6965a 100644
--- a/absl/container/CMakeLists.txt
+++ b/absl/container/CMakeLists.txt
@@ -338,6 +338,8 @@ absl_cc_test(
     "-DUNORDERED_SET_CXX17"
   DEPS
     absl::check
+    absl::config
+    absl::container_memory
     absl::flat_hash_set
     absl::hash_generator_testing
     absl::memory
diff --git a/absl/container/flat_hash_set_test.cc b/absl/container/flat_hash_set_test.cc
index 20130f91..a60b4bf5 100644
--- a/absl/container/flat_hash_set_test.cc
+++ b/absl/container/flat_hash_set_test.cc
@@ -14,8 +14,15 @@
 
 #include "absl/container/flat_hash_set.h"
 
+#include <cstdint>
+#include <memory>
+#include <utility>
 #include <vector>
 
+#include "gmock/gmock.h"
+#include "gtest/gtest.h"
+#include "absl/base/config.h"
+#include "absl/container/internal/container_memory.h"
 #include "absl/container/internal/hash_generator_testing.h"
 #include "absl/container/internal/unordered_set_constructor_test.h"
 #include "absl/container/internal/unordered_set_lookup_test.h"
@@ -172,6 +179,64 @@ TEST(FlatHashSet, EraseIf) {
   }
 }
 
+class PoisonInline {
+  int64_t data_;
+
+ public:
+  explicit PoisonInline(int64_t d) : data_(d) {
+    SanitizerPoisonObject(&data_);
+  }
+  PoisonInline(const PoisonInline& that) : PoisonInline(*that) {}
+  ~PoisonInline() { SanitizerUnpoisonObject(&data_); }
+
+  int64_t operator*() const {
+    SanitizerUnpoisonObject(&data_);
+    const int64_t ret = data_;
+    SanitizerPoisonObject(&data_);
+    return ret;
+  }
+  template <typename H>
+  friend H AbslHashValue(H h, const PoisonInline& pi) {
+    return H::combine(std::move(h), *pi);
+  }
+  bool operator==(const PoisonInline& rhs) const { return **this == *rhs; }
+};
+
+// Tests that we don't touch the poison_ member of PoisonInline.
+TEST(FlatHashSet, PoisonInline) {
+  PoisonInline a(0), b(1);
+  {  // basic usage
+    flat_hash_set<PoisonInline> set;
+    set.insert(a);
+    EXPECT_THAT(set, UnorderedElementsAre(a));
+    set.insert(b);
+    EXPECT_THAT(set, UnorderedElementsAre(a, b));
+    set.erase(a);
+    EXPECT_THAT(set, UnorderedElementsAre(b));
+    set.rehash(0);  // shrink to inline
+    EXPECT_THAT(set, UnorderedElementsAre(b));
+  }
+  {  // test move constructor from inline to inline
+    flat_hash_set<PoisonInline> set;
+    set.insert(a);
+    flat_hash_set<PoisonInline> set2(std::move(set));
+    EXPECT_THAT(set2, UnorderedElementsAre(a));
+  }
+  {  // test move assignment from inline to inline
+    flat_hash_set<PoisonInline> set, set2;
+    set.insert(a);
+    set2 = std::move(set);
+    EXPECT_THAT(set2, UnorderedElementsAre(a));
+  }
+  {  // test alloc move constructor from inline to inline
+    flat_hash_set<PoisonInline> set;
+    set.insert(a);
+    flat_hash_set<PoisonInline> set2(std::move(set),
+                                     std::allocator<PoisonInline>());
+    EXPECT_THAT(set2, UnorderedElementsAre(a));
+  }
+}
+
 }  // namespace
 }  // namespace container_internal
 ABSL_NAMESPACE_END