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, 5 insertions, 2 deletions

diff --git a/absl/container/internal/common.h b/absl/container/internal/common.h
index 8990f294..030e9d4a 100644
--- a/absl/container/internal/common.h
+++ b/absl/container/internal/common.h
@@ -146,8 +146,11 @@ class node_handle<Policy, PolicyTraits, Alloc,
 
   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 {