Export of internal Abseil changes
--
0c8282d75798c77733eee6167870bcc6acc0bfc1 by Evan Brown <ezb@google.com>:
Provide mutable access to the key in node handles using std::launder when compiled with C++17 or later.
Also, document why we can't provide mutable access to the key without C++17.
Note: we use Policy::mutable_key() because btree already uses Policy::key() internally to get const key access, and we want to avoid calling std::launder unless we need mutable access to the key.
PiperOrigin-RevId: 326519000
--
8018d0c3044400f0a731b0d2d00b606742c98818 by Xiaoyi Zhang <zhangxy@google.com>:
Move `Status` internal symbols from the public header into an internal header file.
PiperOrigin-RevId: 326471847
--
87a7644864ba7c003b0611898aaba1b71c840376 by Abseil Team <absl-team@google.com>:
Avoid a costly divide (the division accounts for 10% of the time spent in the function).
When the division is signed, the compiler has to generate a div. When it is unsigned, it can generate a shift: https://godbolt.org/z/vGfTv4. As per the test above the div, we know that the value is unsigned.
PiperOrigin-RevId: 326453275
GitOrigin-RevId: 0c8282d75798c77733eee6167870bcc6acc0bfc1
Change-Id: I0a953558358055ab3dc6a533d8930698509b1195
diff --git a/CMake/AbseilDll.cmake b/CMake/AbseilDll.cmake
index af7c004..7958ace 100644
--- a/CMake/AbseilDll.cmake
+++ b/CMake/AbseilDll.cmake
@@ -174,6 +174,7 @@
"random/uniform_int_distribution.h"
"random/uniform_real_distribution.h"
"random/zipf_distribution.h"
+ "status/internal/status_internal.h"
"status/status.h"
"status/status.cc"
"status/status_payload_printer.h"
diff --git a/absl/container/btree_map.h b/absl/container/btree_map.h
index bb450ea..448ac48 100644
--- a/absl/container/btree_map.h
+++ b/absl/container/btree_map.h
@@ -325,6 +325,11 @@
// does not contain an element with a matching key, this function returns an
// empty node handle.
//
+ // NOTE: when compiled in an earlier version of C++ than C++17,
+ // `node_type::key()` returns a const reference to the key instead of a
+ // mutable reference. We cannot safely return a mutable reference without
+ // std::launder (which is not available before C++17).
+ //
// NOTE: In this context, `node_type` refers to the C++17 concept of a
// move-only type that owns and provides access to the elements in associative
// containers (https://en.cppreference.com/w/cpp/container/node_handle).
@@ -652,6 +657,11 @@
// does not contain an element with a matching key, this function returns an
// empty node handle.
//
+ // NOTE: when compiled in an earlier version of C++ than C++17,
+ // `node_type::key()` returns a const reference to the key instead of a
+ // mutable reference. We cannot safely return a mutable reference without
+ // std::launder (which is not available before C++17).
+ //
// NOTE: In this context, `node_type` refers to the C++17 concept of a
// move-only type that owns and provides access to the elements in associative
// containers (https://en.cppreference.com/w/cpp/container/node_handle).
diff --git a/absl/container/btree_test.cc b/absl/container/btree_test.cc
index 0c5f936..4370420 100644
--- a/absl/container/btree_test.cc
+++ b/absl/container/btree_test.cc
@@ -2551,6 +2551,35 @@
}
#endif
+// This test requires std::launder for mutable key access in node handles.
+#if defined(__cpp_lib_launder) && __cpp_lib_launder >= 201606
+TEST(Btree, NodeHandleMutableKeyAccess) {
+ {
+ absl::btree_map<std::string, std::string> map;
+
+ map["key1"] = "mapped";
+
+ auto nh = map.extract(map.begin());
+ nh.key().resize(3);
+ map.insert(std::move(nh));
+
+ EXPECT_THAT(map, ElementsAre(Pair("key", "mapped")));
+ }
+ // Also for multimap.
+ {
+ absl::btree_multimap<std::string, std::string> map;
+
+ map.emplace("key1", "mapped");
+
+ auto nh = map.extract(map.begin());
+ nh.key().resize(3);
+ map.insert(std::move(nh));
+
+ EXPECT_THAT(map, ElementsAre(Pair("key", "mapped")));
+ }
+}
+#endif
+
} // namespace
} // namespace container_internal
ABSL_NAMESPACE_END
diff --git a/absl/container/flat_hash_map.h b/absl/container/flat_hash_map.h
index fcb70d8..dbd37d3 100644
--- a/absl/container/flat_hash_map.h
+++ b/absl/container/flat_hash_map.h
@@ -383,6 +383,11 @@
// key value and returns a node handle owning that extracted data. If the
// `flat_hash_map` does not contain an element with a matching key, this
// function returns an empty node handle.
+ //
+ // NOTE: when compiled in an earlier version of C++ than C++17,
+ // `node_type::key()` returns a const reference to the key instead of a
+ // mutable reference. We cannot safely return a mutable reference without
+ // std::launder (which is not available before C++17).
using Base::extract;
// flat_hash_map::merge()
diff --git a/absl/container/flat_hash_map_test.cc b/absl/container/flat_hash_map_test.cc
index 2823c32..89ec60c 100644
--- a/absl/container/flat_hash_map_test.cc
+++ b/absl/container/flat_hash_map_test.cc
@@ -267,6 +267,21 @@
}
}
+// This test requires std::launder for mutable key access in node handles.
+#if defined(__cpp_lib_launder) && __cpp_lib_launder >= 201606
+TEST(FlatHashMap, NodeHandleMutableKeyAccess) {
+ flat_hash_map<std::string, std::string> map;
+
+ map["key1"] = "mapped";
+
+ auto nh = map.extract(map.begin());
+ nh.key().resize(3);
+ map.insert(std::move(nh));
+
+ EXPECT_THAT(map, testing::ElementsAre(Pair("key", "mapped")));
+}
+#endif
+
} // namespace
} // namespace container_internal
ABSL_NAMESPACE_END
diff --git a/absl/container/internal/btree.h b/absl/container/internal/btree.h
index 293e577..4d40573 100644
--- a/absl/container/internal/btree.h
+++ b/absl/container/internal/btree.h
@@ -292,6 +292,11 @@
}
static const Key &key(const slot_type *s) { return slot_policy::key(s); }
static const Key &key(slot_type *s) { return slot_policy::key(s); }
+ // For use in node handle.
+ static auto mutable_key(slot_type *s)
+ -> decltype(slot_policy::mutable_key(s)) {
+ return slot_policy::mutable_key(s);
+ }
static mapped_type &value(value_type *value) { return value->second; }
};
@@ -1043,7 +1048,7 @@
#endif
}
- enum {
+ enum : uint32_t {
kNodeValues = node_type::kNodeValues,
kMinNodeValues = kNodeValues / 2,
};
diff --git a/absl/container/internal/common.h b/absl/container/internal/common.h
index 8990f29..030e9d4 100644
--- a/absl/container/internal/common.h
+++ b/absl/container/internal/common.h
@@ -146,8 +146,11 @@
constexpr node_handle() {}
- auto key() const -> decltype(PolicyTraits::key(std::declval<slot_type*>())) {
- return PolicyTraits::key(this->slot());
+ // When C++17 is available, we can use std::launder to provide mutable
+ // access to the key. Otherwise, we provide const access.
+ auto key() const
+ -> decltype(PolicyTraits::mutable_key(std::declval<slot_type*>())) {
+ return PolicyTraits::mutable_key(this->slot());
}
mapped_type& mapped() const {
diff --git a/absl/container/internal/container_memory.h b/absl/container/internal/container_memory.h
index c7777a9..d02c576 100644
--- a/absl/container/internal/container_memory.h
+++ b/absl/container/internal/container_memory.h
@@ -18,6 +18,7 @@
#include <cassert>
#include <cstddef>
#include <memory>
+#include <new>
#include <tuple>
#include <type_traits>
#include <utility>
@@ -352,6 +353,20 @@
return slot->value;
}
+ // When C++17 is available, we can use std::launder to provide mutable
+ // access to the key for use in node handle.
+#if defined(__cpp_lib_launder) && __cpp_lib_launder >= 201606
+ static K& mutable_key(slot_type* slot) {
+ // Still check for kMutableKeys so that we can avoid calling std::launder
+ // unless necessary because it can interfere with optimizations.
+ return kMutableKeys::value ? slot->key
+ : *std::launder(const_cast<K*>(
+ std::addressof(slot->value.first)));
+ }
+#else // !(defined(__cpp_lib_launder) && __cpp_lib_launder >= 201606)
+ static const K& mutable_key(slot_type* slot) { return key(slot); }
+#endif
+
static const K& key(const slot_type* slot) {
return kMutableKeys::value ? slot->key : slot->value.first;
}
diff --git a/absl/container/internal/hash_policy_traits.h b/absl/container/internal/hash_policy_traits.h
index 3e1209c..46c97b1 100644
--- a/absl/container/internal/hash_policy_traits.h
+++ b/absl/container/internal/hash_policy_traits.h
@@ -17,6 +17,7 @@
#include <cstddef>
#include <memory>
+#include <new>
#include <type_traits>
#include <utility>
@@ -29,15 +30,34 @@
// Defines how slots are initialized/destroyed/moved.
template <class Policy, class = void>
struct hash_policy_traits {
+ // The type of the keys stored in the hashtable.
+ using key_type = typename Policy::key_type;
+
private:
struct ReturnKey {
- // We return `Key` here.
+ // When C++17 is available, we can use std::launder to provide mutable
+ // access to the key for use in node handle.
+#if defined(__cpp_lib_launder) && __cpp_lib_launder >= 201606
+ template <class Key,
+ absl::enable_if_t<std::is_lvalue_reference<Key>::value, int> = 0>
+ static key_type& Impl(Key&& k, int) {
+ return *std::launder(
+ const_cast<key_type*>(std::addressof(std::forward<Key>(k))));
+ }
+#endif
+
+ template <class Key>
+ static Key Impl(Key&& k, char) {
+ return std::forward<Key>(k);
+ }
+
// When Key=T&, we forward the lvalue reference.
// When Key=T, we return by value to avoid a dangling reference.
// eg, for string_hash_map.
template <class Key, class... Args>
- Key operator()(Key&& k, const Args&...) const {
- return std::forward<Key>(k);
+ auto operator()(Key&& k, const Args&...) const
+ -> decltype(Impl(std::forward<Key>(k), 0)) {
+ return Impl(std::forward<Key>(k), 0);
}
};
@@ -52,9 +72,6 @@
// The actual object stored in the hash table.
using slot_type = typename Policy::slot_type;
- // The type of the keys stored in the hashtable.
- using key_type = typename Policy::key_type;
-
// The argument type for insertions into the hashtable. This is different
// from value_type for increased performance. See initializer_list constructor
// and insert() member functions for more details.
@@ -156,7 +173,7 @@
// Returns the "key" portion of the slot.
// Used for node handle manipulation.
template <class P = Policy>
- static auto key(slot_type* slot)
+ static auto mutable_key(slot_type* slot)
-> decltype(P::apply(ReturnKey(), element(slot))) {
return P::apply(ReturnKey(), element(slot));
}
diff --git a/absl/container/node_hash_map.h b/absl/container/node_hash_map.h
index 174b971..9852ff7 100644
--- a/absl/container/node_hash_map.h
+++ b/absl/container/node_hash_map.h
@@ -374,6 +374,11 @@
// key value and returns a node handle owning that extracted data. If the
// `node_hash_map` does not contain an element with a matching key, this
// function returns an empty node handle.
+ //
+ // NOTE: when compiled in an earlier version of C++ than C++17,
+ // `node_type::key()` returns a const reference to the key instead of a
+ // mutable reference. We cannot safely return a mutable reference without
+ // std::launder (which is not available before C++17).
using Base::extract;
// node_hash_map::merge()
diff --git a/absl/container/node_hash_map_test.cc b/absl/container/node_hash_map_test.cc
index 5d74b81..8f59a1e 100644
--- a/absl/container/node_hash_map_test.cc
+++ b/absl/container/node_hash_map_test.cc
@@ -254,6 +254,21 @@
}
}
+// This test requires std::launder for mutable key access in node handles.
+#if defined(__cpp_lib_launder) && __cpp_lib_launder >= 201606
+TEST(NodeHashMap, NodeHandleMutableKeyAccess) {
+ node_hash_map<std::string, std::string> map;
+
+ map["key1"] = "mapped";
+
+ auto nh = map.extract(map.begin());
+ nh.key().resize(3);
+ map.insert(std::move(nh));
+
+ EXPECT_THAT(map, testing::ElementsAre(Pair("key", "mapped")));
+}
+#endif
+
} // namespace
} // namespace container_internal
ABSL_NAMESPACE_END
diff --git a/absl/status/BUILD.bazel b/absl/status/BUILD.bazel
index d164252..c4c5e49 100644
--- a/absl/status/BUILD.bazel
+++ b/absl/status/BUILD.bazel
@@ -31,6 +31,7 @@
cc_library(
name = "status",
srcs = [
+ "internal/status_internal.h",
"status.cc",
"status_payload_printer.cc",
],
diff --git a/absl/status/CMakeLists.txt b/absl/status/CMakeLists.txt
index c041d69..b48989d 100644
--- a/absl/status/CMakeLists.txt
+++ b/absl/status/CMakeLists.txt
@@ -19,6 +19,7 @@
HDRS
"status.h"
SRCS
+ "internal/status_internal.h"
"status.cc"
"status_payload_printer.h"
"status_payload_printer.cc"
diff --git a/absl/status/internal/status_internal.h b/absl/status/internal/status_internal.h
new file mode 100644
index 0000000..1f82b8e
--- /dev/null
+++ b/absl/status/internal/status_internal.h
@@ -0,0 +1,51 @@
+// Copyright 2019 The Abseil Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+#ifndef ABSL_STATUS_INTERNAL_STATUS_INTERNAL_H_
+#define ABSL_STATUS_INTERNAL_STATUS_INTERNAL_H_
+
+#include <string>
+
+#include "absl/container/inlined_vector.h"
+#include "absl/strings/cord.h"
+
+namespace absl {
+ABSL_NAMESPACE_BEGIN
+
+enum class StatusCode : int;
+
+namespace status_internal {
+
+// Container for status payloads.
+struct Payload {
+ std::string type_url;
+ absl::Cord payload;
+};
+
+using Payloads = absl::InlinedVector<Payload, 1>;
+
+// Reference-counted representation of Status data.
+struct StatusRep {
+ std::atomic<int32_t> ref;
+ absl::StatusCode code;
+ std::string message;
+ std::unique_ptr<status_internal::Payloads> payloads;
+};
+
+absl::StatusCode MapToLocalCode(int value);
+} // namespace status_internal
+
+ABSL_NAMESPACE_END
+} // namespace absl
+
+#endif // ABSL_STATUS_INTERNAL_STATUS_INTERNAL_H_
diff --git a/absl/status/status.h b/absl/status/status.h
index 4253062..8097b05 100644
--- a/absl/status/status.h
+++ b/absl/status/status.h
@@ -18,6 +18,7 @@
#include <string>
#include "absl/container/inlined_vector.h"
+#include "absl/status/internal/status_internal.h"
#include "absl/strings/cord.h"
#include "absl/types/optional.h"
@@ -164,27 +165,6 @@
// Streams StatusCodeToString(code) to `os`.
std::ostream& operator<<(std::ostream& os, StatusCode code);
-namespace status_internal {
-
-// Container for status payloads.
-struct Payload {
- std::string type_url;
- absl::Cord payload;
-};
-
-using Payloads = absl::InlinedVector<Payload, 1>;
-
-// Reference-counted representation of Status data.
-struct StatusRep {
- std::atomic<int32_t> ref;
- absl::StatusCode code;
- std::string message;
- std::unique_ptr<status_internal::Payloads> payloads;
-};
-
-absl::StatusCode MapToLocalCode(int value);
-} // namespace status_internal
-
class ABSL_MUST_USE_RESULT Status final {
public:
// Creates an OK status with no message or payload.
