Export of internal Abseil changes

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5e45aadfb89e366dedd1fcad5034a76c5c10ad76 by James Y Knight <jyknight@google.com>:

Correct the conditions for std::{optional,variant,any} availability on Apple platforms.

Before XCode 12.5, the availability declarations incorrectly excluded one release on which the features were in fact available. This was corrected in https://github.com/llvm/llvm-project/commit/7fb40e1569dd66292b647f4501b85517e9247953

Unfortunately, we cannot simply switch abseil to the corrected versions, as that will cause build failures when using the older XCode toolchain. So, we check the version, and choose the correct set of versions for the toolchain in use.

PiperOrigin-RevId: 407667302

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376fa06cde048e536e9447336b27bebf598ed4ea by Greg Falcon <gfalcon@google.com>:

Cord implementation change: Add a new CordRepCrc node type.

This is an implementation detail that will allow storing expected CRCs alongside cord data.  This node is intended only to live at the top of Cord trees.

PiperOrigin-RevId: 407587140
GitOrigin-RevId: 5e45aadfb89e366dedd1fcad5034a76c5c10ad76
Change-Id: Iea3ca001c0cbb4deec8286b5581b30dc172a9918

1 files changed, 31 insertions, 12 deletions

diff --git a/absl/base/config.h b/absl/base/config.h
index d3cad682..ae7a5a15 100644
--- a/absl/base/config.h
+++ b/absl/base/config.h
@@ -520,22 +520,41 @@ static_assert(ABSL_INTERNAL_INLINE_NAMESPACE_STR[0] != 'h' ||
 #error "absl endian detection needs to be set up for your compiler"
 #endif
 
-// macOS 10.13 and iOS 10.11 don't let you use <any>, <optional>, or <variant>
-// even though the headers exist and are publicly noted to work.  See
-// https://github.com/abseil/abseil-cpp/issues/207 and
+// macOS < 10.13 and iOS < 11 don't let you use <any>, <optional>, or <variant>
+// even though the headers exist and are publicly noted to work, because the
+// libc++ shared library shipped on the system doesn't have the requisite
+// exported symbols.  See https://github.com/abseil/abseil-cpp/issues/207 and
 // https://developer.apple.com/documentation/xcode_release_notes/xcode_10_release_notes
+//
 // libc++ spells out the availability requirements in the file
 // llvm-project/libcxx/include/__config via the #define
 // _LIBCPP_AVAILABILITY_BAD_OPTIONAL_ACCESS.
-#if defined(__APPLE__) && defined(_LIBCPP_VERSION) && \
-  ((defined(__ENVIRONMENT_MAC_OS_X_VERSION_MIN_REQUIRED__) && \
-   __ENVIRONMENT_MAC_OS_X_VERSION_MIN_REQUIRED__ < 101400) || \
-  (defined(__ENVIRONMENT_IPHONE_OS_VERSION_MIN_REQUIRED__) && \
-   __ENVIRONMENT_IPHONE_OS_VERSION_MIN_REQUIRED__ < 120000) || \
-  (defined(__ENVIRONMENT_WATCH_OS_VERSION_MIN_REQUIRED__) && \
-   __ENVIRONMENT_WATCH_OS_VERSION_MIN_REQUIRED__ < 50000) || \
-  (defined(__ENVIRONMENT_TV_OS_VERSION_MIN_REQUIRED__) && \
-   __ENVIRONMENT_TV_OS_VERSION_MIN_REQUIRED__ < 120000))
+//
+// Unfortunately, Apple initially mis-stated the requirements as macOS < 10.14
+// and iOS < 12 in the libc++ headers. This was corrected by
+// https://github.com/llvm/llvm-project/commit/7fb40e1569dd66292b647f4501b85517e9247953
+// which subsequently made it into the XCode 12.5 release. We need to match the
+// old (incorrect) conditions when built with old XCode, but can use the
+// corrected earlier versions with new XCode.
+#if defined(__APPLE__) && defined(_LIBCPP_VERSION) &&               \
+    ((_LIBCPP_VERSION >= 11000 && /* XCode 12.5 or later: */        \
+      ((defined(__ENVIRONMENT_MAC_OS_X_VERSION_MIN_REQUIRED__) &&   \
+        __ENVIRONMENT_MAC_OS_X_VERSION_MIN_REQUIRED__ < 101300) ||  \
+       (defined(__ENVIRONMENT_IPHONE_OS_VERSION_MIN_REQUIRED__) &&  \
+        __ENVIRONMENT_IPHONE_OS_VERSION_MIN_REQUIRED__ < 110000) || \
+       (defined(__ENVIRONMENT_WATCH_OS_VERSION_MIN_REQUIRED__) &&   \
+        __ENVIRONMENT_WATCH_OS_VERSION_MIN_REQUIRED__ < 40000) ||   \
+       (defined(__ENVIRONMENT_TV_OS_VERSION_MIN_REQUIRED__) &&      \
+        __ENVIRONMENT_TV_OS_VERSION_MIN_REQUIRED__ < 110000))) ||   \
+     (_LIBCPP_VERSION < 11000 && /* Pre-XCode 12.5: */              \
+      ((defined(__ENVIRONMENT_MAC_OS_X_VERSION_MIN_REQUIRED__) &&   \
+        __ENVIRONMENT_MAC_OS_X_VERSION_MIN_REQUIRED__ < 101400) ||  \
+       (defined(__ENVIRONMENT_IPHONE_OS_VERSION_MIN_REQUIRED__) &&  \
+        __ENVIRONMENT_IPHONE_OS_VERSION_MIN_REQUIRED__ < 120000) || \
+       (defined(__ENVIRONMENT_WATCH_OS_VERSION_MIN_REQUIRED__) &&   \
+        __ENVIRONMENT_WATCH_OS_VERSION_MIN_REQUIRED__ < 50000) ||   \
+       (defined(__ENVIRONMENT_TV_OS_VERSION_MIN_REQUIRED__) &&      \
+        __ENVIRONMENT_TV_OS_VERSION_MIN_REQUIRED__ < 120000))))
 #define ABSL_INTERNAL_APPLE_CXX17_TYPES_UNAVAILABLE 1
 #else
 #define ABSL_INTERNAL_APPLE_CXX17_TYPES_UNAVAILABLE 0