Export of internal Abseil changes

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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

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8018d0c3044400f0a731b0d2d00b606742c98818 by Xiaoyi Zhang <zhangxy@google.com>:

Move `Status` internal symbols from the public header into an internal header file.

PiperOrigin-RevId: 326471847

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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

1 files changed, 29 insertions, 0 deletions

diff --git a/absl/container/btree_test.cc b/absl/container/btree_test.cc
index 0c5f9368..43704206 100644
--- a/absl/container/btree_test.cc
+++ b/absl/container/btree_test.cc
@@ -2551,6 +2551,35 @@ TEST(Btree, HeterogeneousInsertOrAssign) {
 }
 #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