Add validation against use of moved-from hash tables.

We enable this validation when sanitizers are enabled rather than in debug mode because debug mode can be enabled/disabled separately in different translation units, which can cause bugs for this type of validation. E.g. a hashtable that was moved from in a TU with debug enabled is then destroyed in a TU with debug disabled.

PiperOrigin-RevId: 668492783
Change-Id: Ifab6894de0890aa0a7d8ea338b53b6759b097cb1

absl/container/internal/raw_hash_set.h

diff --git a/absl/container/internal/raw_hash_set.h b/absl/container/internal/raw_hash_set.h
index 711dabe..c371832 100644
--- a/absl/container/internal/raw_hash_set.h
+++ b/absl/container/internal/raw_hash_set.h
@@ -545,6 +545,7 @@
   kAboveMaxValidCapacity = ~size_t{} - 100,
   kReentrance,
   kDestroyed,
+  kMovedFrom,
 };
 
 // Returns a pointer to a control byte group that can be used by empty tables.
@@ -2402,6 +2403,10 @@
            alignof(slot_type) <= alignof(HeapOrSoo);
   }
 
+  constexpr static size_t DefaultCapacity() {
+    return SooEnabled() ? SooCapacity() : 0;
+  }
+
   // Whether `size` fits in the SOO capacity of this table.
   bool fits_in_soo(size_t size) const {
     return SooEnabled() && size <= SooCapacity();
@@ -2639,7 +2644,7 @@
       const allocator_type& alloc = allocator_type())
       : settings_(CommonFields::CreateDefault<SooEnabled()>(), hash, eq,
                   alloc) {
-    if (bucket_count > (SooEnabled() ? SooCapacity() : 0)) {
+    if (bucket_count > DefaultCapacity()) {
       resize(NormalizeCapacity(bucket_count));
     }
   }
@@ -2822,7 +2827,7 @@
       transfer(soo_slot(), that.soo_slot());
     }
     that.common() = CommonFields::CreateDefault<SooEnabled()>();
-    maybe_increment_generation_or_rehash_on_move();
+    annotate_for_bug_detection_on_move(that);
   }
 
   raw_hash_set(raw_hash_set&& that, const allocator_type& a)
@@ -2830,7 +2835,7 @@
                   that.eq_ref(), a) {
     if (a == that.alloc_ref()) {
       swap_common(that);
-      maybe_increment_generation_or_rehash_on_move();
+      annotate_for_bug_detection_on_move(that);
     } else {
       move_elements_allocs_unequal(std::move(that));
     }
@@ -2896,15 +2901,19 @@
   size_t size() const { return common().size(); }
   size_t capacity() const {
     const size_t cap = common().capacity();
-    // Compiler complains when using functions in assume so use local variables.
-    ABSL_ATTRIBUTE_UNUSED static constexpr bool kEnabled = SooEnabled();
-    ABSL_ATTRIBUTE_UNUSED static constexpr size_t kCapacity = SooCapacity();
-    ABSL_ASSUME(!kEnabled || cap >= kCapacity);
+    // Compiler complains when using functions in ASSUME so use local variable.
+    ABSL_ATTRIBUTE_UNUSED static constexpr size_t kDefaultCapacity =
+        DefaultCapacity();
+    ABSL_ASSUME(cap >= kDefaultCapacity);
     return cap;
   }
   size_t max_size() const { return (std::numeric_limits<size_t>::max)(); }
 
   ABSL_ATTRIBUTE_REINITIALIZES void clear() {
+    if (SwisstableGenerationsEnabled() &&
+        capacity() == InvalidCapacity::kMovedFrom) {
+      common().set_capacity(DefaultCapacity());
+    }
     AssertNotDebugCapacity();
     // Iterating over this container is O(bucket_count()). When bucket_count()
     // is much greater than size(), iteration becomes prohibitively expensive.
@@ -3586,6 +3595,10 @@
   }
 
   inline void destructor_impl() {
+    if (SwisstableGenerationsEnabled() &&
+        capacity() == InvalidCapacity::kMovedFrom) {
+      return;
+    }
     if (capacity() == 0) return;
     if (is_soo()) {
       if (!empty()) {
@@ -3759,8 +3772,16 @@
     move_common(that_is_full_soo, that.alloc_ref(), common(), std::move(tmp));
   }
 
-  void maybe_increment_generation_or_rehash_on_move() {
-    if (!SwisstableGenerationsEnabled() || capacity() == 0 || is_soo()) {
+  void annotate_for_bug_detection_on_move(
+      ABSL_ATTRIBUTE_UNUSED raw_hash_set& that) {
+    // We only enable moved-from validation when generations are enabled (rather
+    // than using NDEBUG) to avoid issues in which NDEBUG is enabled in some
+    // translation units but not in others.
+    if (SwisstableGenerationsEnabled() && this != &that) {
+      that.common().set_capacity(InvalidCapacity::kMovedFrom);
+    }
+    if (!SwisstableGenerationsEnabled() || capacity() == DefaultCapacity() ||
+        capacity() > kAboveMaxValidCapacity) {
       return;
     }
     common().increment_generation();
@@ -3782,7 +3803,7 @@
     CopyAlloc(alloc_ref(), that.alloc_ref(),
               std::integral_constant<bool, propagate_alloc>());
     that.common() = CommonFields::CreateDefault<SooEnabled()>();
-    maybe_increment_generation_or_rehash_on_move();
+    annotate_for_bug_detection_on_move(that);
     return *this;
   }
 
@@ -3796,7 +3817,7 @@
     }
     if (!that.is_soo()) that.dealloc();
     that.common() = CommonFields::CreateDefault<SooEnabled()>();
-    maybe_increment_generation_or_rehash_on_move();
+    annotate_for_bug_detection_on_move(that);
     return *this;
   }
 
@@ -3875,27 +3896,30 @@
   // Asserts for correctness that we run on find/find_or_prepare_insert.
   template <class K>
   void AssertOnFind(ABSL_ATTRIBUTE_UNUSED const K& key) {
-#ifdef NDEBUG
-    return;
-#endif
     AssertHashEqConsistent(key);
     AssertNotDebugCapacity();
   }
 
   // Asserts that the capacity is not a sentinel invalid value.
-  // TODO(b/296061262): also add asserts for moved-from state.
   void AssertNotDebugCapacity() const {
     assert(capacity() != InvalidCapacity::kReentrance &&
-           "reentrant container access during element construction/destruction "
+           "Reentrant container access during element construction/destruction "
            "is not allowed.");
     assert(capacity() != InvalidCapacity::kDestroyed &&
-           "use of destroyed hash table.");
+           "Use of destroyed hash table.");
+    if (SwisstableGenerationsEnabled() &&
+        ABSL_PREDICT_FALSE(capacity() == InvalidCapacity::kMovedFrom)) {
+      ABSL_RAW_LOG(FATAL, "Use of moved-from hash table.");
+    }
   }
 
   // Asserts that hash and equal functors provided by the user are consistent,
   // meaning that `eq(k1, k2)` implies `hash(k1)==hash(k2)`.
   template <class K>
   void AssertHashEqConsistent(const K& key) {
+#ifdef NDEBUG
+    return;
+#endif
     // If the hash/eq functors are known to be consistent, then skip validation.
     if (std::is_same<hasher, absl::container_internal::StringHash>::value &&
         std::is_same<key_equal, absl::container_internal::StringEq>::value) {

absl/container/internal/raw_hash_set_test.cc

diff --git a/absl/container/internal/raw_hash_set_test.cc b/absl/container/internal/raw_hash_set_test.cc
index 81397ad..3d5f59a 100644
--- a/absl/container/internal/raw_hash_set_test.cc
+++ b/absl/container/internal/raw_hash_set_test.cc
@@ -3674,6 +3674,29 @@
 #endif
 }
 
+TEST(Table, MovedFromCallsFail) {
+  if (!SwisstableGenerationsEnabled()) {
+    GTEST_SKIP() << "Moved-from checks only enabled in sanitizer mode.";
+    return;
+  }
+
+  {
+    ABSL_ATTRIBUTE_UNUSED IntTable t1, t2;
+    t1.insert(1);
+    t2 = std::move(t1);
+    // NOLINTNEXTLINE(bugprone-use-after-move)
+    EXPECT_DEATH_IF_SUPPORTED(t1.contains(1), "");
+  }
+  {
+    ABSL_ATTRIBUTE_UNUSED IntTable t1;
+    t1.insert(1);
+    ABSL_ATTRIBUTE_UNUSED IntTable t2(std::move(t1));
+    // NOLINTNEXTLINE(bugprone-use-after-move)
+    EXPECT_DEATH_IF_SUPPORTED(t1.contains(1), "");
+    t1.clear();  // Clearing a moved-from table is allowed.
+  }
+}
+
 }  // namespace
 }  // namespace container_internal
 ABSL_NAMESPACE_END