Export of internal Abseil changes

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8726480d631a3736347f542dab5628d5e2ace3c1 by Mark Barolak <mbar@google.com>:

Import of CCTZ from GitHub.

PiperOrigin-RevId: 323414814

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abc4a382a29fb857432e0e13a8c21ebe808f9828 by Abseil Team <absl-team@google.com>:

Fix buffer overflow when the result of demangling doesn't fit.

PiperOrigin-RevId: 323392968

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7ed3e514519a971322d0a3333c7e85ed1f2a5f71 by Gennadiy Rozental <rogeeff@google.com>:

Move ABSL_DEPRECATED and ABSL_FALLTHROUGH_INTENDED from base.h into attribute.h.

PiperOrigin-RevId: 323137526

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fc0afdb0792d565065d25feb9680972218355f90 by Xiaoyi Zhang <zhangxy@google.com>:

Add documentation for `absl::StatusCode`.

PiperOrigin-RevId: 323065623
GitOrigin-RevId: 8726480d631a3736347f542dab5628d5e2ace3c1
Change-Id: I9d39650e49ff265cd2dafee302013694e97c813f

1 files changed, 79 insertions, 0 deletions

diff --git a/absl/base/attributes.h b/absl/base/attributes.h
index c4fd81b0..2cf4b1e8 100644
--- a/absl/base/attributes.h
+++ b/absl/base/attributes.h
@@ -594,6 +594,85 @@
 #define ABSL_ATTRIBUTE_FUNC_ALIGN(bytes)
 #endif
 
+// ABSL_FALLTHROUGH_INTENDED
+//
+// Annotates implicit fall-through between switch labels, allowing a case to
+// indicate intentional fallthrough and turn off warnings about any lack of a
+// `break` statement. The ABSL_FALLTHROUGH_INTENDED macro should be followed by
+// a semicolon and can be used in most places where `break` can, provided that
+// no statements exist between it and the next switch label.
+//
+// Example:
+//
+//  switch (x) {
+//    case 40:
+//    case 41:
+//      if (truth_is_out_there) {
+//        ++x;
+//        ABSL_FALLTHROUGH_INTENDED;  // Use instead of/along with annotations
+//                                    // in comments
+//      } else {
+//        return x;
+//      }
+//    case 42:
+//      ...
+//
+// Notes: when compiled with clang in C++11 mode, the ABSL_FALLTHROUGH_INTENDED
+// macro is expanded to the [[clang::fallthrough]] attribute, which is analysed
+// when  performing switch labels fall-through diagnostic
+// (`-Wimplicit-fallthrough`). See clang documentation on language extensions
+// for details:
+// https://clang.llvm.org/docs/AttributeReference.html#fallthrough-clang-fallthrough
+//
+// When used with unsupported compilers, the ABSL_FALLTHROUGH_INTENDED macro
+// has no effect on diagnostics. In any case this macro has no effect on runtime
+// behavior and performance of code.
+#ifdef ABSL_FALLTHROUGH_INTENDED
+#error "ABSL_FALLTHROUGH_INTENDED should not be defined."
+#endif
+
+// TODO(zhangxy): Use c++17 standard [[fallthrough]] macro, when supported.
+#if defined(__clang__) && defined(__has_warning)
+#if __has_feature(cxx_attributes) && __has_warning("-Wimplicit-fallthrough")
+#define ABSL_FALLTHROUGH_INTENDED [[clang::fallthrough]]
+#endif
+#elif defined(__GNUC__) && __GNUC__ >= 7
+#define ABSL_FALLTHROUGH_INTENDED [[gnu::fallthrough]]
+#endif
+
+#ifndef ABSL_FALLTHROUGH_INTENDED
+#define ABSL_FALLTHROUGH_INTENDED \
+  do {                            \
+  } while (0)
+#endif
+
+// ABSL_DEPRECATED()
+//
+// Marks a deprecated class, struct, enum, function, method and variable
+// declarations. The macro argument is used as a custom diagnostic message (e.g.
+// suggestion of a better alternative).
+//
+// Examples:
+//
+//   class ABSL_DEPRECATED("Use Bar instead") Foo {...};
+//
+//   ABSL_DEPRECATED("Use Baz() instead") void Bar() {...}
+//
+//   template <typename T>
+//   ABSL_DEPRECATED("Use DoThat() instead")
+//   void DoThis();
+//
+// Every usage of a deprecated entity will trigger a warning when compiled with
+// clang's `-Wdeprecated-declarations` option. This option is turned off by
+// default, but the warnings will be reported by clang-tidy.
+#if defined(__clang__) && __cplusplus >= 201103L
+#define ABSL_DEPRECATED(message) __attribute__((deprecated(message)))
+#endif
+
+#ifndef ABSL_DEPRECATED
+#define ABSL_DEPRECATED(message)
+#endif
+
 // ABSL_CONST_INIT
 //
 // A variable declaration annotated with the `ABSL_CONST_INIT` attribute will