Export of internal Abseil changes

--
0f6565955231dc74ebad62ef32a18c457afa2dc7 by Abseil Team <absl-team@google.com>:

Document guarantee that we do not move from rvalue arguments if no insertion happens with absl::raw_hash_map::try_emplace, as done with std::unordered_map::try_emplace.

PiperOrigin-RevId: 264430409

--
292e6b9e08fa689e8400d7f2db94cbcab29d5889 by CJ Johnson <johnsoncj@google.com>:

Removes use of aligned_storage in FixedArray and InlinedVector in favor of aligned char buffers.

PiperOrigin-RevId: 264385559

--
aa0b19ad11ae5702022feee0e2e6434cfb28c9e9 by Derek Mauro <dmauro@google.com>:

Make the unit tests for absl::any, absl::optional, and absl::variant
no-ops when these types are just aliases for the corresponding std::
types. We have no way to fix standard library implementation bugs, so
don't bother working around them.

Also disable the corresponding exception-safety tests as well when
exceptions are not enabled.

Fixes https://github.com/abseil/abseil-cpp/pull/360

PiperOrigin-RevId: 264382050

--
65896a911f36481b89b4712c83b91c90a76b64e8 by Abseil Team <absl-team@google.com>:

Improve documentation on erase

PiperOrigin-RevId: 264381266
GitOrigin-RevId: 0f6565955231dc74ebad62ef32a18c457afa2dc7
Change-Id: I74b9bd2ddf84526014104f17e87de70bd3fe65fa

20 files changed, 140 insertions, 30 deletions

diff --git a/absl/container/BUILD.bazel b/absl/container/BUILD.bazel
index 45c90528..ec890190 100644
--- a/absl/container/BUILD.bazel
+++ b/absl/container/BUILD.bazel
@@ -448,6 +448,7 @@ cc_library(
     linkopts = ABSL_DEFAULT_LINKOPTS,
     deps = [
         ":hash_policy_testing",
+        "//absl/memory",
         "//absl/meta:type_traits",
         "//absl/strings",
     ],
diff --git a/absl/container/CMakeLists.txt b/absl/container/CMakeLists.txt
index fb966ec7..638c2759 100644
--- a/absl/container/CMakeLists.txt
+++ b/absl/container/CMakeLists.txt
@@ -510,6 +510,7 @@ absl_cc_library(
     ${ABSL_TEST_COPTS}
   DEPS
     absl::hash_policy_testing
+    absl::memory
     absl::meta
     absl::strings
   TESTONLY
diff --git a/absl/container/fixed_array.h b/absl/container/fixed_array.h
index 2a8240ae..70e94ad5 100644
--- a/absl/container/fixed_array.h
+++ b/absl/container/fixed_array.h
@@ -31,7 +31,6 @@
 #define ABSL_CONTAINER_FIXED_ARRAY_H_
 
 #include <algorithm>
-#include <array>
 #include <cassert>
 #include <cstddef>
 #include <initializer_list>
@@ -386,8 +385,7 @@ class FixedArray {
   //     error: call to int __builtin___sprintf_chk(etc...)
   //     will always overflow destination buffer [-Werror]
   //
-  template <typename OuterT = value_type,
-            typename InnerT = absl::remove_extent_t<OuterT>,
+  template <typename OuterT, typename InnerT = absl::remove_extent_t<OuterT>,
             size_t InnerN = std::extent<OuterT>::value>
   struct StorageElementWrapper {
     InnerT array[InnerN];
@@ -396,8 +394,6 @@ class FixedArray {
   using StorageElement =
       absl::conditional_t<std::is_array<value_type>::value,
                           StorageElementWrapper<value_type>, value_type>;
-  using StorageElementBuffer =
-      absl::aligned_storage_t<sizeof(StorageElement), alignof(StorageElement)>;
 
   static pointer AsValueType(pointer ptr) { return ptr; }
   static pointer AsValueType(StorageElementWrapper<value_type>* ptr) {
@@ -407,25 +403,25 @@ class FixedArray {
   static_assert(sizeof(StorageElement) == sizeof(value_type), "");
   static_assert(alignof(StorageElement) == alignof(value_type), "");
 
-  struct NonEmptyInlinedStorage {
-    StorageElement* data() {
-      return reinterpret_cast<StorageElement*>(inlined_storage_.data());
-    }
+  class NonEmptyInlinedStorage {
+   public:
+    StorageElement* data() { return reinterpret_cast<StorageElement*>(buff_); }
+    void AnnotateConstruct(size_type n);
+    void AnnotateDestruct(size_type n);
 
 #ifdef ADDRESS_SANITIZER
     void* RedzoneBegin() { return &redzone_begin_; }
     void* RedzoneEnd() { return &redzone_end_ + 1; }
 #endif  // ADDRESS_SANITIZER
 
-    void AnnotateConstruct(size_type);
-    void AnnotateDestruct(size_type);
-
+   private:
     ADDRESS_SANITIZER_REDZONE(redzone_begin_);
-    std::array<StorageElementBuffer, inline_elements> inlined_storage_;
+    alignas(StorageElement) char buff_[sizeof(StorageElement[inline_elements])];
     ADDRESS_SANITIZER_REDZONE(redzone_end_);
   };
 
-  struct EmptyInlinedStorage {
+  class EmptyInlinedStorage {
+   public:
     StorageElement* data() { return nullptr; }
     void AnnotateConstruct(size_type) {}
     void AnnotateDestruct(size_type) {}
@@ -459,9 +455,7 @@ class FixedArray {
     size_type size() const { return size_alloc_.template get<0>(); }
     StorageElement* begin() const { return data_; }
     StorageElement* end() const { return begin() + size(); }
-    allocator_type& alloc() {
-      return size_alloc_.template get<1>();
-    }
+    allocator_type& alloc() { return size_alloc_.template get<1>(); }
 
    private:
     static bool UsingInlinedStorage(size_type n) {
diff --git a/absl/container/flat_hash_map.h b/absl/container/flat_hash_map.h
index 0bc501b1..5c16ac88 100644
--- a/absl/container/flat_hash_map.h
+++ b/absl/container/flat_hash_map.h
@@ -360,6 +360,10 @@ class flat_hash_map : public absl::container_internal::raw_hash_map<
   // Inserts (via copy or move) the element of the specified key into the
   // `flat_hash_map` using the position of `hint` as a non-binding suggestion
   // for where to begin the insertion search.
+  //
+  // All `try_emplace()` overloads make the same guarantees regarding rvalue
+  // arguments as `std::unordered_map::try_emplace()`, namely that these
+  // functions will not move from rvalue arguments if insertions do not happen.
   using Base::try_emplace;
 
   // flat_hash_map::extract()
diff --git a/absl/container/flat_hash_map_test.cc b/absl/container/flat_hash_map_test.cc
index ebcb560f..6cff1a25 100644
--- a/absl/container/flat_hash_map_test.cc
+++ b/absl/container/flat_hash_map_test.cc
@@ -14,6 +14,8 @@
 
 #include "absl/container/flat_hash_map.h"
 
+#include <memory>
+
 #include "absl/container/internal/hash_generator_testing.h"
 #include "absl/container/internal/unordered_map_constructor_test.h"
 #include "absl/container/internal/unordered_map_lookup_test.h"
@@ -46,6 +48,11 @@ INSTANTIATE_TYPED_TEST_SUITE_P(FlatHashMap, LookupTest, MapTypes);
 INSTANTIATE_TYPED_TEST_SUITE_P(FlatHashMap, MembersTest, MapTypes);
 INSTANTIATE_TYPED_TEST_SUITE_P(FlatHashMap, ModifiersTest, MapTypes);
 
+using UniquePtrMapTypes = ::testing::Types<Map<int, std::unique_ptr<int>>>;
+
+INSTANTIATE_TYPED_TEST_SUITE_P(FlatHashMap, UniquePtrModifiersTest,
+                               UniquePtrMapTypes);
+
 TEST(FlatHashMap, StandardLayout) {
   struct Int {
     explicit Int(size_t value) : value(value) {}
diff --git a/absl/container/internal/hash_generator_testing.h b/absl/container/internal/hash_generator_testing.h
index 27fb84f5..477215cd 100644
--- a/absl/container/internal/hash_generator_testing.h
+++ b/absl/container/internal/hash_generator_testing.h
@@ -19,6 +19,7 @@
 #define ABSL_CONTAINER_INTERNAL_HASH_GENERATOR_TESTING_H_
 
 #include <stdint.h>
+
 #include <algorithm>
 #include <iosfwd>
 #include <random>
@@ -27,6 +28,7 @@
 #include <utility>
 
 #include "absl/container/internal/hash_policy_testing.h"
+#include "absl/memory/memory.h"
 #include "absl/meta/type_traits.h"
 #include "absl/strings/string_view.h"
 
@@ -129,6 +131,13 @@ struct Generator<std::tuple<Ts...>> {
   }
 };
 
+template <class T>
+struct Generator<std::unique_ptr<T>> {
+  std::unique_ptr<T> operator()() const {
+    return absl::make_unique<T>(Generator<T>()());
+  }
+};
+
 template <class U>
 struct Generator<U, absl::void_t<decltype(std::declval<U&>().key()),
                                 decltype(std::declval<U&>().value())>>
diff --git a/absl/container/internal/inlined_vector.h b/absl/container/internal/inlined_vector.h
index d7c616cf..54369c85 100644
--- a/absl/container/internal/inlined_vector.h
+++ b/absl/container/internal/inlined_vector.h
@@ -445,9 +445,7 @@ class Storage {
   };
 
   struct Inlined {
-    using InlinedDataElement =
-        absl::aligned_storage_t<sizeof(value_type), alignof(value_type)>;
-    InlinedDataElement inlined_data[N];
+    alignas(value_type) char inlined_data[sizeof(value_type[N])];
   };
 
   union Data {
diff --git a/absl/container/internal/raw_hash_map.h b/absl/container/internal/raw_hash_map.h
index 6a9c730c..7dad120a 100644
--- a/absl/container/internal/raw_hash_map.h
+++ b/absl/container/internal/raw_hash_map.h
@@ -109,6 +109,9 @@ class raw_hash_map : public raw_hash_set<Policy, Hash, Eq, Alloc> {
     return insert_or_assign(k, v).first;
   }
 
+  // All `try_emplace()` overloads make the same guarantees regarding rvalue
+  // arguments as `std::unordered_map::try_emplace()`, namely that these
+  // functions will not move from rvalue arguments if insertions do not happen.
   template <class K = key_type, class... Args,
             typename std::enable_if<
                 !std::is_convertible<K, const_iterator>::value, int>::type = 0,
diff --git a/absl/container/internal/raw_hash_set.h b/absl/container/internal/raw_hash_set.h
index 656e9806..2e6f4dd3 100644
--- a/absl/container/internal/raw_hash_set.h
+++ b/absl/container/internal/raw_hash_set.h
@@ -1133,15 +1133,16 @@ class raw_hash_set {
   }
 
   // Erases the element pointed to by `it`.  Unlike `std::unordered_set::erase`,
-  // this method returns void to reduce algorithmic complexity to O(1).  In
-  // order to erase while iterating across a map, use the following idiom (which
-  // also works for standard containers):
+  // this method returns void to reduce algorithmic complexity to O(1).  The
+  // iterator is invalidated, so any increment should be done before calling
+  // erase.  In order to erase while iterating across a map, use the following
+  // idiom (which also works for standard containers):
   //
   // for (auto it = m.begin(), end = m.end(); it != end;) {
+  //   // `erase()` will invalidate `it`, so advance `it` first.
+  //   auto copy_it = it++;
   //   if (<pred>) {
-  //     m.erase(it++);
-  //   } else {
-  //     ++it;
+  //     m.erase(copy_it);
   //   }
   // }
   void erase(const_iterator cit) { erase(cit.inner_); }
diff --git a/absl/container/internal/unordered_map_modifiers_test.h b/absl/container/internal/unordered_map_modifiers_test.h
index 52a1092e..f6aff542 100644
--- a/absl/container/internal/unordered_map_modifiers_test.h
+++ b/absl/container/internal/unordered_map_modifiers_test.h
@@ -15,6 +15,8 @@
 #ifndef ABSL_CONTAINER_INTERNAL_UNORDERED_MAP_MODIFIERS_TEST_H_
 #define ABSL_CONTAINER_INTERNAL_UNORDERED_MAP_MODIFIERS_TEST_H_
 
+#include <memory>
+
 #include "gmock/gmock.h"
 #include "gtest/gtest.h"
 #include "absl/container/internal/hash_generator_testing.h"
@@ -267,6 +269,45 @@ REGISTER_TYPED_TEST_CASE_P(ModifiersTest, Clear, Insert, InsertHint,
                            Emplace, EmplaceHint, TryEmplace, TryEmplaceHint,
                            Erase, EraseRange, EraseKey, Swap);
 
+template <typename Type>
+struct is_unique_ptr : std::false_type {};
+
+template <typename Type>
+struct is_unique_ptr<std::unique_ptr<Type>> : std::true_type {};
+
+template <class UnordMap>
+class UniquePtrModifiersTest : public ::testing::Test {
+ protected:
+  UniquePtrModifiersTest() {
+    static_assert(is_unique_ptr<typename UnordMap::mapped_type>::value,
+                  "UniquePtrModifiersTyest may only be called with a "
+                  "std::unique_ptr value type.");
+  }
+};
+
+TYPED_TEST_SUITE_P(UniquePtrModifiersTest);
+
+// Test that we do not move from rvalue arguments if an insertion does not
+// happen.
+TYPED_TEST_P(UniquePtrModifiersTest, TryEmplace) {
+#ifdef UNORDERED_MAP_CXX17
+  using T = hash_internal::GeneratedType<TypeParam>;
+  using V = typename TypeParam::mapped_type;
+  T val = hash_internal::Generator<T>()();
+  TypeParam m;
+  auto p = m.try_emplace(val.first, std::move(val.second));
+  EXPECT_TRUE(p.second);
+  // A moved from std::unique_ptr is guaranteed to be nullptr.
+  EXPECT_EQ(val.second, nullptr);
+  T val2 = {val.first, hash_internal::Generator<V>()()};
+  p = m.try_emplace(val2.first, std::move(val2.second));
+  EXPECT_FALSE(p.second);
+  EXPECT_NE(val2.second, nullptr);
+#endif
+}
+
+REGISTER_TYPED_TEST_SUITE_P(UniquePtrModifiersTest, TryEmplace);
+
 }  // namespace container_internal
 }  // namespace absl
 
diff --git a/absl/container/internal/unordered_map_test.cc b/absl/container/internal/unordered_map_test.cc
index 72567eac..114b342d 100644
--- a/absl/container/internal/unordered_map_test.cc
+++ b/absl/container/internal/unordered_map_test.cc
@@ -12,6 +12,7 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
+#include <memory>
 #include <unordered_map>
 
 #include "absl/container/internal/unordered_map_constructor_test.h"
@@ -35,6 +36,13 @@ INSTANTIATE_TYPED_TEST_SUITE_P(UnorderedMap, LookupTest, MapTypes);
 INSTANTIATE_TYPED_TEST_SUITE_P(UnorderedMap, MembersTest, MapTypes);
 INSTANTIATE_TYPED_TEST_SUITE_P(UnorderedMap, ModifiersTest, MapTypes);
 
+using UniquePtrMapTypes = ::testing::Types<std::unordered_map<
+    int, std::unique_ptr<int>, StatefulTestingHash, StatefulTestingEqual,
+    Alloc<std::pair<const int, std::unique_ptr<int>>>>>;
+
+INSTANTIATE_TYPED_TEST_SUITE_P(UnorderedMap, UniquePtrModifiersTest,
+                               UniquePtrMapTypes);
+
 }  // namespace
 }  // namespace container_internal
 }  // namespace absl
diff --git a/absl/container/node_hash_map.h b/absl/container/node_hash_map.h
index a841f5ab..a718842b 100644
--- a/absl/container/node_hash_map.h
+++ b/absl/container/node_hash_map.h
@@ -351,6 +351,10 @@ class node_hash_map
   // Inserts (via copy or move) the element of the specified key into the
   // `node_hash_map` using the position of `hint` as a non-binding suggestion
   // for where to begin the insertion search.
+  //
+  // All `try_emplace()` overloads make the same guarantees regarding rvalue
+  // arguments as `std::unordered_map::try_emplace()`, namely that these
+  // functions will not move from rvalue arguments if insertions do not happen.
   using Base::try_emplace;
 
   // node_hash_map::extract()
diff --git a/absl/types/BUILD.bazel b/absl/types/BUILD.bazel
index 6dd4e142..037d499a 100644
--- a/absl/types/BUILD.bazel
+++ b/absl/types/BUILD.bazel
@@ -111,6 +111,7 @@ cc_test(
     linkopts = ABSL_EXCEPTIONS_FLAG_LINKOPTS + ABSL_DEFAULT_LINKOPTS,
     deps = [
         ":any",
+        "//absl/base:config",
         "//absl/base:exception_safety_testing",
         "@com_google_googletest//:gtest_main",
     ],
@@ -240,6 +241,7 @@ cc_test(
     linkopts = ABSL_EXCEPTIONS_FLAG_LINKOPTS + ABSL_DEFAULT_LINKOPTS,
     deps = [
         ":optional",
+        "//absl/base:config",
         "//absl/base:exception_safety_testing",
         "@com_google_googletest//:gtest_main",
     ],
diff --git a/absl/types/CMakeLists.txt b/absl/types/CMakeLists.txt
index ddae7f2a..1f7fde09 100644
--- a/absl/types/CMakeLists.txt
+++ b/absl/types/CMakeLists.txt
@@ -105,6 +105,7 @@ absl_cc_test(
     ${ABSL_EXCEPTIONS_FLAG_LINKOPTS}
   DEPS
     absl::any
+    absl::config
     absl::exception_safety_testing
     gmock_main
 )
@@ -256,6 +257,7 @@ absl_cc_test(
     ${ABSL_EXCEPTIONS_FLAG_LINKOPTS}
   DEPS
     absl::optional
+    absl::config
     absl::exception_safety_testing
     gmock_main
 )
diff --git a/absl/types/any_exception_safety_test.cc b/absl/types/any_exception_safety_test.cc
index 5d7d8a5c..17d7f5d7 100644
--- a/absl/types/any_exception_safety_test.cc
+++ b/absl/types/any_exception_safety_test.cc
@@ -14,6 +14,12 @@
 
 #include "absl/types/any.h"
 
+#include "absl/base/config.h"
+
+// This test is a no-op when absl::any is an alias for std::any and when
+// exceptions are not enabled.
+#if !defined(ABSL_HAVE_STD_ANY) && defined(ABSL_HAVE_EXCEPTIONS)
+
 #include <typeinfo>
 #include <vector>
 
@@ -136,8 +142,6 @@ TEST(AnyExceptionSafety, Assignment) {
   EXPECT_TRUE(strong_empty_any_tester.Test(move));
 }
 
-// libstdc++ std::any fails this test
-#if !defined(ABSL_HAVE_STD_ANY)
 TEST(AnyExceptionSafety, Emplace) {
   auto initial_val =
       absl::any{absl::in_place_type_t<Thrower>(), 1, testing::nothrow_ctor};
@@ -163,6 +167,7 @@ TEST(AnyExceptionSafety, Emplace) {
   EXPECT_TRUE(empty_tester.Test(emp_thrower));
   EXPECT_TRUE(empty_tester.Test(emp_throwervec));
 }
-#endif  // ABSL_HAVE_STD_ANY
 
 }  // namespace
+
+#endif  // #if !defined(ABSL_HAVE_STD_ANY) && defined(ABSL_HAVE_EXCEPTIONS)
diff --git a/absl/types/any_test.cc b/absl/types/any_test.cc
index 87104721..4a848ae4 100644
--- a/absl/types/any_test.cc
+++ b/absl/types/any_test.cc
@@ -14,6 +14,9 @@
 
 #include "absl/types/any.h"
 
+// This test is a no-op when absl::any is an alias for std::any.
+#if !defined(ABSL_HAVE_STD_ANY)
+
 #include <initializer_list>
 #include <type_traits>
 #include <utility>
@@ -774,3 +777,5 @@ TEST(AnyTest, FailedEmplace) {
 }
 
 }  // namespace
+
+#endif  // #if !defined(ABSL_HAVE_STD_ANY)
diff --git a/absl/types/optional_exception_safety_test.cc b/absl/types/optional_exception_safety_test.cc
index aaf8ebcd..f99e35c0 100644
--- a/absl/types/optional_exception_safety_test.cc
+++ b/absl/types/optional_exception_safety_test.cc
@@ -14,6 +14,12 @@
 
 #include "absl/types/optional.h"
 
+#include "absl/base/config.h"
+
+// This test is a no-op when absl::optional is an alias for std::optional and
+// when exceptions are not enabled.
+#if !defined(ABSL_HAVE_STD_OPTIONAL) && defined(ABSL_HAVE_EXCEPTIONS)
+
 #include "gtest/gtest.h"
 #include "absl/base/internal/exception_safety_testing.h"
 
@@ -280,3 +286,5 @@ TEST(OptionalExceptionSafety, NothrowMoveAssign) {
 }  // namespace
 
 }  // namespace absl
+
+#endif  // #if !defined(ABSL_HAVE_STD_OPTIONAL) && defined(ABSL_HAVE_EXCEPTIONS)
diff --git a/absl/types/optional_test.cc b/absl/types/optional_test.cc
index e6a36eb8..e005affb 100644
--- a/absl/types/optional_test.cc
+++ b/absl/types/optional_test.cc
@@ -14,6 +14,9 @@
 
 #include "absl/types/optional.h"
 
+// This test is a no-op when absl::optional is an alias for std::optional.
+#if !defined(ABSL_HAVE_STD_OPTIONAL)
+
 #include <string>
 #include <type_traits>
 #include <utility>
@@ -1654,3 +1657,5 @@ TEST(optionalTest, InPlaceTSFINAEBug) {
 #endif  // !defined(__EMSCRIPTEN__)
 
 }  // namespace
+
+#endif  // #if !defined(ABSL_HAVE_STD_OPTIONAL)
diff --git a/absl/types/variant_exception_safety_test.cc b/absl/types/variant_exception_safety_test.cc
index 76beb595..fd7e6c7f 100644
--- a/absl/types/variant_exception_safety_test.cc
+++ b/absl/types/variant_exception_safety_test.cc
@@ -14,6 +14,12 @@
 
 #include "absl/types/variant.h"
 
+#include "absl/base/config.h"
+
+// This test is a no-op when absl::variant is an alias for std::variant and when
+// exceptions are not enabled.
+#if !defined(ABSL_HAVE_STD_VARIANT) && defined(ABSL_HAVE_EXCEPTIONS)
+
 #include <iostream>
 #include <memory>
 #include <utility>
@@ -21,7 +27,6 @@
 
 #include "gmock/gmock.h"
 #include "gtest/gtest.h"
-#include "absl/base/config.h"
 #include "absl/base/internal/exception_safety_testing.h"
 #include "absl/memory/memory.h"
 
@@ -521,3 +526,5 @@ TEST(VariantExceptionSafetyTest, Swap) {
 }  // namespace absl
 
 #endif  // !defined(ABSL_INTERNAL_MSVC_2017_DBG_MODE)
+
+#endif  // #if !defined(ABSL_HAVE_STD_VARIANT) && defined(ABSL_HAVE_EXCEPTIONS)
diff --git a/absl/types/variant_test.cc b/absl/types/variant_test.cc
index 85201b3e..56a6e01c 100644
--- a/absl/types/variant_test.cc
+++ b/absl/types/variant_test.cc
@@ -19,6 +19,9 @@
 
 #include "absl/types/variant.h"
 
+// This test is a no-op when absl::variant is an alias for std::variant.
+#if !defined(ABSL_HAVE_STD_VARIANT)
+
 #include <algorithm>
 #include <cstddef>
 #include <functional>
@@ -2705,3 +2708,5 @@ TEST(VariantTest, MoveCtorBug) {
 
 }  // namespace
 }  // namespace absl
+
+#endif  // #if !defined(ABSL_HAVE_STD_VARIANT)