Export of internal Abseil changes

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76c5eb1cf346a1a64e0a5e2edf032546d600075a by Andy Getzendanner <durandal@google.com>:

Fix stacktrace on aarch64 architecture. Fixes #805

Import of https://github.com/abseil/abseil-cpp/pull/827

PiperOrigin-RevId: 340886173

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28f48f7bcadd4681854cddb0a7736d26d7dab000 by Andy Getzendanner <durandal@google.com>:

Some attribute cleanups in and around statusor:
* mark statusor_internal::Helper::Crash ABSL_ATTRIBUTE_NORETURN
* add ABSL_INTERNAL_UNREACHABLE to ABSL_INTERNAL_LOG when severity is FATAL
* create ABSL_INTERNAL_UNREACHABLE to wrap __builtin_unreachable and __assume(0)
* use ABSL_ATTRIBUTE_NONNULL instead of __builtin_unreachable in statusor_internal::PlacementNew (https://godbolt.org/z/n691fa)

PiperOrigin-RevId: 340868438

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33905d1d2d01eb6f81b04abaf24170bfebb6df09 by Andy Getzendanner <durandal@google.com>:

moved deleted functions to public for better compiler errors.

Import of https://github.com/abseil/abseil-cpp/pull/828

PiperOrigin-RevId: 340863976

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5e502222dfc3f5a0ef146535a9e16c743b005092 by Jorg Brown <jorg@google.com>:

ConvertibleToStringView wastes a lot of cycles initializing members just to reset them immediately after. Only initialize the string storage when needed. This makes StrSplit() 0-30% faster depending on the use case.

PiperOrigin-RevId: 340732039
GitOrigin-RevId: 76c5eb1cf346a1a64e0a5e2edf032546d600075a
Change-Id: I2ba1f717c4eaad384cd0a22694fd05f9e6a2d8fa

1 files changed, 18 insertions, 33 deletions

diff --git a/absl/strings/internal/str_split_internal.h b/absl/strings/internal/str_split_internal.h
index 76924771..49ec5392 100644
--- a/absl/strings/internal/str_split_internal.h
+++ b/absl/strings/internal/str_split_internal.h
@@ -66,56 +66,41 @@ class ConvertibleToStringView {
 
   // Matches rvalue strings and moves their data to a member.
   ConvertibleToStringView(std::string&& s)  // NOLINT(runtime/explicit)
-      : copy_(std::move(s)), value_(copy_), self_referential_(true) {}
+      : copy_(std::move(s)), value_(copy_) {}
 
   ConvertibleToStringView(const ConvertibleToStringView& other)
-      : value_(other.value_), self_referential_(other.self_referential_) {
-    if (other.self_referential_) {
-      new (&copy_) std::string(other.copy_);
-      value_ = copy_;
-    }
-  }
+      : copy_(other.copy_),
+        value_(other.IsSelfReferential() ? copy_ : other.value_) {}
 
-  ConvertibleToStringView(ConvertibleToStringView&& other)
-      : value_(other.value_), self_referential_(other.self_referential_) {
-    if (other.self_referential_) {
-      new (&copy_) std::string(std::move(other.copy_));
-      value_ = copy_;
-    }
+  ConvertibleToStringView(ConvertibleToStringView&& other) {
+    StealMembers(std::move(other));
   }
 
   ConvertibleToStringView& operator=(ConvertibleToStringView other) {
-    this->~ConvertibleToStringView();
-    new (this) ConvertibleToStringView(std::move(other));
+    StealMembers(std::move(other));
     return *this;
   }
 
   absl::string_view value() const { return value_; }
 
-  ~ConvertibleToStringView() { MaybeReleaseCopy(); }
-
  private:
-  void MaybeReleaseCopy() {
-    if (self_referential_) {
-      // An explicit destructor call cannot be a qualified name such as
-      // std::string. The "using" declaration works around this
-      // issue by creating an unqualified name for the destructor.
-      using string_type = std::string;
-      copy_.~string_type();
+  // Returns true if ctsp's value refers to its internal copy_ member.
+  bool IsSelfReferential() const { return value_.data() == copy_.data(); }
+
+  void StealMembers(ConvertibleToStringView&& other) {
+    if (other.IsSelfReferential()) {
+      copy_ = std::move(other.copy_);
+      value_ = copy_;
+      other.value_ = other.copy_;
+    } else {
+      value_ = other.value_;
     }
   }
-  struct Unused {  // MSVC disallows unions with only 1 member.
-  };
+
   // Holds the data moved from temporary std::string arguments. Declared first
   // so that 'value' can refer to 'copy_'.
-  union {
-    std::string copy_;
-    Unused unused_;
-  };
-
+  std::string copy_;
   absl::string_view value_;
-  // true if value_ refers to the internal copy_ member.
-  bool self_referential_ = false;
 };
 
 // An iterator that enumerates the parts of a string from a Splitter. The text