merge(3p/absl): subtree merge of Abseil up to e19260f r/1889

... notably, this includes Abseil's own StatusOr type, which conflicted with our implementation (that was taken from TensorFlow). Change-Id: Ie7d6764b64055caaeb8dc7b6b9d066291e6b538f
author: Vincent Ambo <mail@tazj.in> 2020-11-21T13·43+0100
committer: Vincent Ambo <mail@tazj.in> 2020-11-21T14·48+0100
commit: 082c006c04343a78d87b6c6ab3608c25d6213c3f (patch)
tree: 16e6f04f8d1d1d2d67e8e917d5e7bb48c1b60375 /third_party/abseil_cpp/absl/strings
parent: cc27324d0226953943f408ce3c69ad7d648e005e (diff)
40 files changed, 2309 insertions, 451 deletions
diff --git a/third_party/abseil_cpp/absl/strings/BUILD.bazel b/third_party/abseil_cpp/absl/strings/BUILD.bazel
index 8220896d3d34..30a8dd28b2d1 100644
--- a/third_party/abseil_cpp/absl/strings/BUILD.bazel
+++ b/third_party/abseil_cpp/absl/strings/BUILD.bazel
@@ -54,6 +54,7 @@ cc_library(
         "ascii.h",
         "charconv.h",
         "escaping.h",
+        "internal/string_constant.h",
         "match.h",
         "numbers.h",
         "str_cat.h",
@@ -223,6 +224,19 @@ cc_test(
 )
 
 cc_test(
+    name = "string_constant_test",
+    size = "small",
+    srcs = ["internal/string_constant_test.cc"],
+    copts = ABSL_TEST_COPTS,
+    visibility = ["//visibility:private"],
+    deps = [
+        ":strings",
+        "//absl/meta:type_traits",
+        "@com_google_googletest//:gtest_main",
+    ],
+)
+
+cc_test(
     name = "string_view_benchmark",
     srcs = ["string_view_benchmark.cc"],
     copts = ABSL_TEST_COPTS,
@@ -258,6 +272,8 @@ cc_library(
     visibility = ["//visibility:private"],
     deps = [
         ":strings",
+        "//absl/base:base_internal",
+        "//absl/container:compressed_tuple",
         "//absl/meta:type_traits",
     ],
 )
@@ -277,7 +293,6 @@ cc_library(
         ":str_format",
         ":strings",
         "//absl/base",
-        "//absl/base:base_internal",
         "//absl/base:core_headers",
         "//absl/base:endian",
         "//absl/base:raw_logging_internal",
@@ -720,6 +735,7 @@ cc_test(
     visibility = ["//visibility:private"],
     deps = [
         ":str_format_internal",
+        ":strings",
         "//absl/base:raw_logging_internal",
         "//absl/types:optional",
         "@com_google_googletest//:gtest_main",
diff --git a/third_party/abseil_cpp/absl/strings/CMakeLists.txt b/third_party/abseil_cpp/absl/strings/CMakeLists.txt
index c0ea0c8e1d94..2b994a71c07e 100644
--- a/third_party/abseil_cpp/absl/strings/CMakeLists.txt
+++ b/third_party/abseil_cpp/absl/strings/CMakeLists.txt
@@ -21,6 +21,7 @@ absl_cc_library(
     "ascii.h"
     "charconv.h"
     "escaping.h"
+    "internal/string_constant.h"
     "match.h"
     "numbers.h"
     "str_cat.h"
@@ -160,6 +161,19 @@ absl_cc_test(
 
 absl_cc_test(
   NAME
+    string_constant_test
+  SRCS
+    "internal/string_constant_test.cc"
+  COPTS
+    ${ABSL_TEST_COPTS}
+  DEPS
+    absl::strings
+    absl::type_traits
+    gmock_main
+)
+
+absl_cc_test(
+  NAME
     string_view_test
   SRCS
     "string_view_test.cc"
@@ -475,6 +489,7 @@ absl_cc_test(
   COPTS
     ${ABSL_TEST_COPTS}
   DEPS
+    absl::strings
     absl::str_format_internal
     absl::raw_logging_internal
     absl::int128
@@ -547,6 +562,7 @@ absl_cc_library(
   DEPS
     absl::base
     absl::base_internal
+    absl::compressed_tuple
     absl::core_headers
     absl::endian
     absl::fixed_array
diff --git a/third_party/abseil_cpp/absl/strings/cord.cc b/third_party/abseil_cpp/absl/strings/cord.cc
index 68f5398791db..9efd13575039 100644
--- a/third_party/abseil_cpp/absl/strings/cord.cc
+++ b/third_party/abseil_cpp/absl/strings/cord.cc
@@ -50,58 +50,10 @@ using ::absl::cord_internal::CordRepConcat;
 using ::absl::cord_internal::CordRepExternal;
 using ::absl::cord_internal::CordRepSubstring;
 
-// Various representations that we allow
-enum CordRepKind {
-  CONCAT        = 0,
-  EXTERNAL      = 1,
-  SUBSTRING     = 2,
-
-  // We have different tags for different sized flat arrays,
-  // starting with FLAT
-  FLAT          = 3,
-};
-
-namespace {
-
-// Type used with std::allocator for allocating and deallocating
-// `CordRepExternal`. std::allocator is used because it opaquely handles the
-// different new / delete overloads available on a given platform.
-struct alignas(absl::cord_internal::ExternalRepAlignment()) ExternalAllocType {
-  unsigned char value[absl::cord_internal::ExternalRepAlignment()];
-};
-
-// Returns the number of objects to pass in to std::allocator<ExternalAllocType>
-// allocate() and deallocate() to create enough room for `CordRepExternal` with
-// `releaser_size` bytes on the end.
-constexpr size_t GetExternalAllocNumObjects(size_t releaser_size) {
-  // Be sure to round up since `releaser_size` could be smaller than
-  // `sizeof(ExternalAllocType)`.
-  return (sizeof(CordRepExternal) + releaser_size + sizeof(ExternalAllocType) -
-          1) /
-         sizeof(ExternalAllocType);
-}
-
-// Allocates enough memory for `CordRepExternal` and a releaser with size
-// `releaser_size` bytes.
-void* AllocateExternal(size_t releaser_size) {
-  return std::allocator<ExternalAllocType>().allocate(
-      GetExternalAllocNumObjects(releaser_size));
-}
-
-// Deallocates the memory for a `CordRepExternal` assuming it was allocated with
-// a releaser of given size and alignment.
-void DeallocateExternal(CordRepExternal* p, size_t releaser_size) {
-  std::allocator<ExternalAllocType>().deallocate(
-      reinterpret_cast<ExternalAllocType*>(p),
-      GetExternalAllocNumObjects(releaser_size));
-}
-
-// Returns a pointer to the type erased releaser for the given CordRepExternal.
-void* GetExternalReleaser(CordRepExternal* rep) {
-  return rep + 1;
-}
-
-}  // namespace
+using ::absl::cord_internal::CONCAT;
+using ::absl::cord_internal::EXTERNAL;
+using ::absl::cord_internal::FLAT;
+using ::absl::cord_internal::SUBSTRING;
 
 namespace cord_internal {
 
@@ -289,6 +241,7 @@ static void UnrefInternal(CordRep* rep) {
 
   absl::InlinedVector<CordRep*, kInlinedVectorSize> pending;
   while (true) {
+    assert(!rep->refcount.IsImmortal());
     if (rep->tag == CONCAT) {
       CordRepConcat* rep_concat = rep->concat();
       CordRep* right = rep_concat->right;
@@ -304,11 +257,8 @@ static void UnrefInternal(CordRep* rep) {
       }
     } else if (rep->tag == EXTERNAL) {
       CordRepExternal* rep_external = rep->external();
-      absl::string_view data(rep_external->base, rep->length);
-      void* releaser = GetExternalReleaser(rep_external);
-      size_t releaser_size = rep_external->releaser_invoker(releaser, data);
-      rep_external->~CordRepExternal();
-      DeallocateExternal(rep_external, releaser_size);
+      assert(rep_external->releaser_invoker != nullptr);
+      rep_external->releaser_invoker(rep_external);
       rep = nullptr;
     } else if (rep->tag == SUBSTRING) {
       CordRepSubstring* rep_substring = rep->substring();
@@ -458,18 +408,12 @@ static CordRep* NewTree(const char* data,
 
 namespace cord_internal {
 
-ExternalRepReleaserPair NewExternalWithUninitializedReleaser(
-    absl::string_view data, ExternalReleaserInvoker invoker,
-    size_t releaser_size) {
+void InitializeCordRepExternal(absl::string_view data, CordRepExternal* rep) {
   assert(!data.empty());
-
-  void* raw_rep = AllocateExternal(releaser_size);
-  auto* rep = new (raw_rep) CordRepExternal();
   rep->length = data.size();
   rep->tag = EXTERNAL;
   rep->base = data.data();
-  rep->releaser_invoker = invoker;
-  return {VerifyTree(rep), GetExternalReleaser(rep)};
+  VerifyTree(rep);
 }
 
 }  // namespace cord_internal
@@ -493,57 +437,55 @@ static CordRep* NewSubstring(CordRep* child, size_t offset, size_t length) {
 // --------------------------------------------------------------------
 // Cord::InlineRep functions
 
-// This will trigger LNK2005 in MSVC.
-#ifndef COMPILER_MSVC
-const unsigned char Cord::InlineRep::kMaxInline;
-#endif  // COMPILER_MSVC
+constexpr unsigned char Cord::InlineRep::kMaxInline;
 
 inline void Cord::InlineRep::set_data(const char* data, size_t n,
                                       bool nullify_tail) {
   static_assert(kMaxInline == 15, "set_data is hard-coded for a length of 15");
 
-  cord_internal::SmallMemmove(data_, data, n, nullify_tail);
-  data_[kMaxInline] = static_cast<char>(n);
+  cord_internal::SmallMemmove(data_.as_chars, data, n, nullify_tail);
+  set_tagged_size(static_cast<char>(n));
 }
 
 inline char* Cord::InlineRep::set_data(size_t n) {
   assert(n <= kMaxInline);
-  memset(data_, 0, sizeof(data_));
-  data_[kMaxInline] = static_cast<char>(n);
-  return data_;
+  ResetToEmpty();
+  set_tagged_size(static_cast<char>(n));
+  return data_.as_chars;
 }
 
 inline CordRep* Cord::InlineRep::force_tree(size_t extra_hint) {
-  size_t len = data_[kMaxInline];
-  CordRep* result;
+  size_t len = tagged_size();
   if (len > kMaxInline) {
-    memcpy(&result, data_, sizeof(result));
-  } else {
-    result = NewFlat(len + extra_hint);
-    result->length = len;
-    memcpy(result->data, data_, len);
-    set_tree(result);
+    return data_.as_tree.rep;
   }
+
+  CordRep* result = NewFlat(len + extra_hint);
+  result->length = len;
+  static_assert(kMinFlatLength >= sizeof(data_.as_chars), "");
+  memcpy(result->data, data_.as_chars, sizeof(data_.as_chars));
+  set_tree(result);
   return result;
 }
 
 inline void Cord::InlineRep::reduce_size(size_t n) {
-  size_t tag = data_[kMaxInline];
+  size_t tag = tagged_size();
   assert(tag <= kMaxInline);
   assert(tag >= n);
   tag -= n;
-  memset(data_ + tag, 0, n);
-  data_[kMaxInline] = static_cast<char>(tag);
+  memset(data_.as_chars + tag, 0, n);
+  set_tagged_size(static_cast<char>(tag));
 }
 
 inline void Cord::InlineRep::remove_prefix(size_t n) {
-  cord_internal::SmallMemmove(data_, data_ + n, data_[kMaxInline] - n);
+  cord_internal::SmallMemmove(data_.as_chars, data_.as_chars + n,
+                              tagged_size() - n);
   reduce_size(n);
 }
 
 void Cord::InlineRep::AppendTree(CordRep* tree) {
   if (tree == nullptr) return;
-  size_t len = data_[kMaxInline];
+  size_t len = tagged_size();
   if (len == 0) {
     set_tree(tree);
   } else {
@@ -552,8 +494,8 @@ void Cord::InlineRep::AppendTree(CordRep* tree) {
 }
 
 void Cord::InlineRep::PrependTree(CordRep* tree) {
-  if (tree == nullptr) return;
-  size_t len = data_[kMaxInline];
+  assert(tree != nullptr);
+  size_t len = tagged_size();
   if (len == 0) {
     set_tree(tree);
   } else {
@@ -609,11 +551,11 @@ void Cord::InlineRep::GetAppendRegion(char** region, size_t* size,
   }
 
   // Try to fit in the inline buffer if possible.
-  size_t inline_length = data_[kMaxInline];
+  size_t inline_length = tagged_size();
   if (inline_length < kMaxInline && max_length <= kMaxInline - inline_length) {
-    *region = data_ + inline_length;
+    *region = data_.as_chars + inline_length;
     *size = max_length;
-    data_[kMaxInline] = static_cast<char>(inline_length + max_length);
+    set_tagged_size(static_cast<char>(inline_length + max_length));
     return;
   }
 
@@ -637,11 +579,11 @@ void Cord::InlineRep::GetAppendRegion(char** region, size_t* size) {
   const size_t max_length = std::numeric_limits<size_t>::max();
 
   // Try to fit in the inline buffer if possible.
-  size_t inline_length = data_[kMaxInline];
+  size_t inline_length = tagged_size();
   if (inline_length < kMaxInline) {
-    *region = data_ + inline_length;
+    *region = data_.as_chars + inline_length;
     *size = kMaxInline - inline_length;
-    data_[kMaxInline] = kMaxInline;
+    set_tagged_size(kMaxInline);
     return;
   }
 
@@ -676,7 +618,7 @@ static bool RepMemoryUsageLeaf(const CordRep* rep, size_t* total_mem_usage) {
 void Cord::InlineRep::AssignSlow(const Cord::InlineRep& src) {
   ClearSlow();
 
-  memcpy(data_, src.data_, sizeof(data_));
+  data_ = src.data_;
   if (is_tree()) {
     Ref(tree());
   }
@@ -686,7 +628,7 @@ void Cord::InlineRep::ClearSlow() {
   if (is_tree()) {
     Unref(tree());
   }
-  memset(data_, 0, sizeof(data_));
+  ResetToEmpty();
 }
 
 // --------------------------------------------------------------------
@@ -724,12 +666,12 @@ Cord::Cord(T&& src) {
       std::string data;
     };
     const absl::string_view original_data = src;
-    CordRepExternal* rep =
-        static_cast<CordRepExternal*>(absl::cord_internal::NewExternalRep(
-            original_data, StringReleaser{std::move(src)}));
+    auto* rep = static_cast<
+        ::absl::cord_internal::CordRepExternalImpl<StringReleaser>*>(
+        absl::cord_internal::NewExternalRep(
+            original_data, StringReleaser{std::forward<T>(src)}));
     // Moving src may have invalidated its data pointer, so adjust it.
-    rep->base =
-        static_cast<StringReleaser*>(GetExternalReleaser(rep))->data.data();
+    rep->base = rep->template get<0>().data.data();
     contents_.set_tree(rep);
   }
 }
@@ -778,7 +720,7 @@ Cord& Cord::operator=(T&& src) {
   if (src.size() <= kMaxBytesToCopy) {
     *this = absl::string_view(src);
   } else {
-    *this = Cord(std::move(src));
+    *this = Cord(std::forward<T>(src));
   }
   return *this;
 }
@@ -790,11 +732,11 @@ template Cord& Cord::operator=(std::string&& src);
 void Cord::InlineRep::AppendArray(const char* src_data, size_t src_size) {
   if (src_size == 0) return;  // memcpy(_, nullptr, 0) is undefined.
   // Try to fit in the inline buffer if possible.
-  size_t inline_length = data_[kMaxInline];
+  size_t inline_length = tagged_size();
   if (inline_length < kMaxInline && src_size <= kMaxInline - inline_length) {
     // Append new data to embedded array
-    data_[kMaxInline] = static_cast<char>(inline_length + src_size);
-    memcpy(data_ + inline_length, src_data, src_size);
+    set_tagged_size(static_cast<char>(inline_length + src_size));
+    memcpy(data_.as_chars + inline_length, src_data, src_size);
     return;
   }
 
@@ -817,7 +759,7 @@ void Cord::InlineRep::AppendArray(const char* src_data, size_t src_size) {
     const size_t size2 = inline_length + src_size / 10;
     root = NewFlat(std::max<size_t>(size1, size2));
     appended = std::min(src_size, TagToLength(root->tag) - inline_length);
-    memcpy(root->data, data_, inline_length);
+    memcpy(root->data, data_.as_chars, inline_length);
     memcpy(root->data + inline_length, src_data, appended);
     root->length = inline_length + appended;
     set_tree(root);
@@ -901,7 +843,7 @@ void Cord::Append(T&& src) {
   if (src.size() <= kMaxBytesToCopy) {
     Append(absl::string_view(src));
   } else {
-    Append(Cord(std::move(src)));
+    Append(Cord(std::forward<T>(src)));
   }
 }
 
@@ -941,7 +883,7 @@ inline void Cord::Prepend(T&& src) {
   if (src.size() <= kMaxBytesToCopy) {
     Prepend(absl::string_view(src));
   } else {
-    Prepend(Cord(std::move(src)));
+    Prepend(Cord(std::forward<T>(src)));
   }
 }
 
@@ -1126,7 +1068,7 @@ Cord Cord::Subcord(size_t pos, size_t new_size) const {
   } else if (new_size <= InlineRep::kMaxInline) {
     Cord::ChunkIterator it = chunk_begin();
     it.AdvanceBytes(pos);
-    char* dest = sub_cord.contents_.data_;
+    char* dest = sub_cord.contents_.data_.as_chars;
     size_t remaining_size = new_size;
     while (remaining_size > it->size()) {
       cord_internal::SmallMemmove(dest, it->data(), it->size());
@@ -1135,7 +1077,7 @@ Cord Cord::Subcord(size_t pos, size_t new_size) const {
       ++it;
     }
     cord_internal::SmallMemmove(dest, it->data(), remaining_size);
-    sub_cord.contents_.data_[InlineRep::kMaxInline] = new_size;
+    sub_cord.contents_.set_tagged_size(new_size);
   } else {
     sub_cord.contents_.set_tree(NewSubRange(tree, pos, new_size));
   }
@@ -1324,9 +1266,9 @@ bool ComputeCompareResult<bool>(int memcmp_res) {
 // Helper routine. Locates the first flat chunk of the Cord without
 // initializing the iterator.
 inline absl::string_view Cord::InlineRep::FindFlatStartPiece() const {
-  size_t n = data_[kMaxInline];
+  size_t n = tagged_size();
   if (n <= kMaxInline) {
-    return absl::string_view(data_, n);
+    return absl::string_view(data_.as_chars, n);
   }
 
   CordRep* node = tree();
diff --git a/third_party/abseil_cpp/absl/strings/cord.h b/third_party/abseil_cpp/absl/strings/cord.h
index dc987454fafb..5d5c897e663c 100644
--- a/third_party/abseil_cpp/absl/strings/cord.h
+++ b/third_party/abseil_cpp/absl/strings/cord.h
@@ -71,7 +71,6 @@
 #include <type_traits>
 
 #include "absl/base/internal/endian.h"
-#include "absl/base/internal/invoke.h"
 #include "absl/base/internal/per_thread_tls.h"
 #include "absl/base/macros.h"
 #include "absl/base/port.h"
@@ -80,6 +79,7 @@
 #include "absl/meta/type_traits.h"
 #include "absl/strings/internal/cord_internal.h"
 #include "absl/strings/internal/resize_uninitialized.h"
+#include "absl/strings/internal/string_constant.h"
 #include "absl/strings/string_view.h"
 #include "absl/types/optional.h"
 
@@ -126,9 +126,9 @@ class Cord {
       absl::enable_if_t<std::is_same<T, std::string>::value, int>;
 
  public:
-  // Cord::Cord() Constructors
+  // Cord::Cord() Constructors.
 
-  // Creates an empty Cord
+  // Creates an empty Cord.
   constexpr Cord() noexcept;
 
   // Creates a Cord from an existing Cord. Cord is copyable and efficiently
@@ -154,7 +154,7 @@ class Cord {
 
   // Cord::~Cord()
   //
-  // Destructs the Cord
+  // Destructs the Cord.
   ~Cord() {
     if (contents_.is_tree()) DestroyCordSlow();
   }
@@ -173,10 +173,6 @@ class Cord {
   //
   //   * be move constructible
   //   * support `void operator()(absl::string_view) const` or `void operator()`
-  //   * not have alignment requirement greater than what is guaranteed by
-  //     `::operator new`. This alignment is dictated by
-  //     `alignof(std::max_align_t)` (pre-C++17 code) or
-  //     `__STDCPP_DEFAULT_NEW_ALIGNMENT__` (C++17 code).
   //
   // Example:
   //
@@ -592,7 +588,7 @@ class Cord {
 
   // Cord::operator[]
   //
-  // Get the "i"th character of the Cord and returns it, provided that
+  // Gets the "i"th character of the Cord and returns it, provided that
   // 0 <= i < Cord.size().
   //
   // NOTE: This routine is reasonably efficient. It is roughly
@@ -604,8 +600,8 @@ class Cord {
 
   // Cord::TryFlat()
   //
-  // If this cord's representation is a single flat array, return a
-  // string_view referencing that array.  Otherwise return nullopt.
+  // If this cord's representation is a single flat array, returns a
+  // string_view referencing that array.  Otherwise returns nullopt.
   absl::optional<absl::string_view> TryFlat() const;
 
   // Cord::Flatten()
@@ -615,7 +611,7 @@ class Cord {
   // If the cord was already flat, the contents are not modified.
   absl::string_view Flatten();
 
-  // Support absl::Cord as a sink object for absl::Format().
+  // Supports absl::Cord as a sink object for absl::Format().
   friend void AbslFormatFlush(absl::Cord* cord, absl::string_view part) {
     cord->Append(part);
   }
@@ -629,12 +625,20 @@ class Cord {
     return c.HashFragmented(std::move(hash_state));
   }
 
+  // Create a Cord with the contents of StringConstant<T>::value.
+  // No allocations will be done and no data will be copied.
+  // This is an INTERNAL API and subject to change or removal. This API can only
+  // be used by spelling absl::strings_internal::MakeStringConstant, which is
+  // also an internal API.
+  template <typename T>
+  explicit constexpr Cord(strings_internal::StringConstant<T>);
+
  private:
   friend class CordTestPeer;
   friend bool operator==(const Cord& lhs, const Cord& rhs);
   friend bool operator==(const Cord& lhs, absl::string_view rhs);
 
-  // Call the provided function once for each cord chunk, in order.  Unlike
+  // Calls the provided function once for each cord chunk, in order.  Unlike
   // Chunks(), this API will not allocate memory.
   void ForEachChunk(absl::FunctionRef<void(absl::string_view)>) const;
 
@@ -649,19 +653,19 @@ class Cord {
   // InlineRep holds either a tree pointer, or an array of kMaxInline bytes.
   class InlineRep {
    public:
-    static constexpr unsigned char kMaxInline = 15;
+    static constexpr unsigned char kMaxInline = cord_internal::kMaxInline;
     static_assert(kMaxInline >= sizeof(absl::cord_internal::CordRep*), "");
-    // Tag byte & kMaxInline means we are storing a pointer.
-    static constexpr unsigned char kTreeFlag = 1 << 4;
-    // Tag byte & kProfiledFlag means we are profiling the Cord.
-    static constexpr unsigned char kProfiledFlag = 1 << 5;
+    static constexpr unsigned char kTreeFlag = cord_internal::kTreeFlag;
+    static constexpr unsigned char kProfiledFlag = cord_internal::kProfiledFlag;
 
-    constexpr InlineRep() : data_{} {}
+    constexpr InlineRep() : data_() {}
     InlineRep(const InlineRep& src);
     InlineRep(InlineRep&& src);
     InlineRep& operator=(const InlineRep& src);
     InlineRep& operator=(InlineRep&& src) noexcept;
 
+    explicit constexpr InlineRep(cord_internal::InlineData data);
+
     void Swap(InlineRep* rhs);
     bool empty() const;
     size_t size() const;
@@ -678,7 +682,7 @@ class Cord {
     void replace_tree(absl::cord_internal::CordRep* rep);
     // Returns non-null iff was holding a pointer
     absl::cord_internal::CordRep* clear();
-    // Convert to pointer if necessary
+    // Converts to pointer if necessary.
     absl::cord_internal::CordRep* force_tree(size_t extra_hint);
     void reduce_size(size_t n);  // REQUIRES: holding data
     void remove_prefix(size_t n);  // REQUIRES: holding data
@@ -689,16 +693,16 @@ class Cord {
     void GetAppendRegion(char** region, size_t* size, size_t max_length);
     void GetAppendRegion(char** region, size_t* size);
     bool IsSame(const InlineRep& other) const {
-      return memcmp(data_, other.data_, sizeof(data_)) == 0;
+      return memcmp(&data_, &other.data_, sizeof(data_)) == 0;
     }
     int BitwiseCompare(const InlineRep& other) const {
       uint64_t x, y;
-      // Use memcpy to avoid anti-aliasing issues.
-      memcpy(&x, data_, sizeof(x));
-      memcpy(&y, other.data_, sizeof(y));
+      // Use memcpy to avoid aliasing issues.
+      memcpy(&x, &data_, sizeof(x));
+      memcpy(&y, &other.data_, sizeof(y));
       if (x == y) {
-        memcpy(&x, data_ + 8, sizeof(x));
-        memcpy(&y, other.data_ + 8, sizeof(y));
+        memcpy(&x, reinterpret_cast<const char*>(&data_) + 8, sizeof(x));
+        memcpy(&y, reinterpret_cast<const char*>(&other.data_) + 8, sizeof(y));
         if (x == y) return 0;
       }
       return absl::big_endian::FromHost64(x) < absl::big_endian::FromHost64(y)
@@ -711,16 +715,16 @@ class Cord {
       // to 15 bytes does not cause a memory allocation.
       absl::strings_internal::STLStringResizeUninitialized(dst,
                                                            sizeof(data_) - 1);
-      memcpy(&(*dst)[0], data_, sizeof(data_) - 1);
+      memcpy(&(*dst)[0], &data_, sizeof(data_) - 1);
       // erase is faster than resize because the logic for memory allocation is
       // not needed.
-      dst->erase(data_[kMaxInline]);
+      dst->erase(tagged_size());
     }
 
     // Copies the inline contents into `dst`. Assumes the cord is not empty.
     void CopyToArray(char* dst) const;
 
-    bool is_tree() const { return data_[kMaxInline] > kMaxInline; }
+    bool is_tree() const { return tagged_size() > kMaxInline; }
 
    private:
     friend class Cord;
@@ -729,21 +733,29 @@ class Cord {
     // Unrefs the tree, stops profiling, and zeroes the contents
     void ClearSlow();
 
-    // If the data has length <= kMaxInline, we store it in data_[0..len-1],
-    // and store the length in data_[kMaxInline].  Else we store it in a tree
-    // and store a pointer to that tree in data_[0..sizeof(CordRep*)-1].
-    alignas(absl::cord_internal::CordRep*) char data_[kMaxInline + 1];
+    void ResetToEmpty() { data_ = {}; }
+
+    // This uses reinterpret_cast instead of the union to avoid accessing the
+    // inactive union element. The tagged size is not a common prefix.
+    void set_tagged_size(char new_tag) {
+      reinterpret_cast<char*>(&data_)[kMaxInline] = new_tag;
+    }
+    char tagged_size() const {
+      return reinterpret_cast<const char*>(&data_)[kMaxInline];
+    }
+
+    cord_internal::InlineData data_;
   };
   InlineRep contents_;
 
-  // Helper for MemoryUsage()
+  // Helper for MemoryUsage().
   static size_t MemoryUsageAux(const absl::cord_internal::CordRep* rep);
 
-  // Helper for GetFlat() and TryFlat()
+  // Helper for GetFlat() and TryFlat().
   static bool GetFlatAux(absl::cord_internal::CordRep* rep,
                          absl::string_view* fragment);
 
-  // Helper for ForEachChunk()
+  // Helper for ForEachChunk().
   static void ForEachChunkAux(
       absl::cord_internal::CordRep* rep,
       absl::FunctionRef<void(absl::string_view)> callback);
@@ -772,11 +784,11 @@ class Cord {
   absl::cord_internal::CordRep* TakeRep() const&;
   absl::cord_internal::CordRep* TakeRep() &&;
 
-  // Helper for Append()
+  // Helper for Append().
   template <typename C>
   void AppendImpl(C&& src);
 
-  // Helper for AbslHashValue()
+  // Helper for AbslHashValue().
   template <typename H>
   H HashFragmented(H hash_state) const {
     typename H::AbslInternalPiecewiseCombiner combiner;
@@ -842,47 +854,15 @@ inline void SmallMemmove(char* dst, const char* src, size_t n,
   }
 }
 
-struct ExternalRepReleaserPair {
-  CordRep* rep;
-  void* releaser_address;
-};
-
-// Allocates a new external `CordRep` and returns a pointer to it and a pointer
-// to `releaser_size` bytes where the desired releaser can be constructed.
+// Does non-template-specific `CordRepExternal` initialization.
 // Expects `data` to be non-empty.
-ExternalRepReleaserPair NewExternalWithUninitializedReleaser(
-    absl::string_view data, ExternalReleaserInvoker invoker,
-    size_t releaser_size);
-
-struct Rank1 {};
-struct Rank0 : Rank1 {};
-
-template <typename Releaser, typename = ::absl::base_internal::InvokeT<
-                                 Releaser, absl::string_view>>
-void InvokeReleaser(Rank0, Releaser&& releaser, absl::string_view data) {
-  ::absl::base_internal::Invoke(std::forward<Releaser>(releaser), data);
-}
-
-template <typename Releaser,
-          typename = ::absl::base_internal::InvokeT<Releaser>>
-void InvokeReleaser(Rank1, Releaser&& releaser, absl::string_view) {
-  ::absl::base_internal::Invoke(std::forward<Releaser>(releaser));
-}
+void InitializeCordRepExternal(absl::string_view data, CordRepExternal* rep);
 
 // Creates a new `CordRep` that owns `data` and `releaser` and returns a pointer
 // to it, or `nullptr` if `data` was empty.
 template <typename Releaser>
 // NOLINTNEXTLINE - suppress clang-tidy raw pointer return.
 CordRep* NewExternalRep(absl::string_view data, Releaser&& releaser) {
-  static_assert(
-#if defined(__STDCPP_DEFAULT_NEW_ALIGNMENT__)
-      alignof(Releaser) <= __STDCPP_DEFAULT_NEW_ALIGNMENT__,
-#else
-      alignof(Releaser) <= alignof(max_align_t),
-#endif
-      "Releasers with alignment requirement greater than what is returned by "
-      "default `::operator new()` are not supported.");
-
   using ReleaserType = absl::decay_t<Releaser>;
   if (data.empty()) {
     // Never create empty external nodes.
@@ -891,18 +871,10 @@ CordRep* NewExternalRep(absl::string_view data, Releaser&& releaser) {
     return nullptr;
   }
 
-  auto releaser_invoker = [](void* type_erased_releaser, absl::string_view d) {
-    auto* my_releaser = static_cast<ReleaserType*>(type_erased_releaser);
-    InvokeReleaser(Rank0{}, std::move(*my_releaser), d);
-    my_releaser->~ReleaserType();
-    return sizeof(Releaser);
-  };
-
-  ExternalRepReleaserPair external = NewExternalWithUninitializedReleaser(
-      data, releaser_invoker, sizeof(releaser));
-  ::new (external.releaser_address)
-      ReleaserType(std::forward<Releaser>(releaser));
-  return external.rep;
+  CordRepExternal* rep = new CordRepExternalImpl<ReleaserType>(
+      std::forward<Releaser>(releaser), 0);
+  InitializeCordRepExternal(data, rep);
+  return rep;
 }
 
 // Overload for function reference types that dispatches using a function
@@ -923,13 +895,16 @@ Cord MakeCordFromExternal(absl::string_view data, Releaser&& releaser) {
   return cord;
 }
 
+constexpr Cord::InlineRep::InlineRep(cord_internal::InlineData data)
+    : data_(data) {}
+
 inline Cord::InlineRep::InlineRep(const Cord::InlineRep& src) {
-  cord_internal::SmallMemmove(data_, src.data_, sizeof(data_));
+  data_ = src.data_;
 }
 
 inline Cord::InlineRep::InlineRep(Cord::InlineRep&& src) {
-  memcpy(data_, src.data_, sizeof(data_));
-  memset(src.data_, 0, sizeof(data_));
+  data_ = src.data_;
+  src.ResetToEmpty();
 }
 
 inline Cord::InlineRep& Cord::InlineRep::operator=(const Cord::InlineRep& src) {
@@ -937,7 +912,7 @@ inline Cord::InlineRep& Cord::InlineRep::operator=(const Cord::InlineRep& src) {
     return *this;
   }
   if (!is_tree() && !src.is_tree()) {
-    cord_internal::SmallMemmove(data_, src.data_, sizeof(data_));
+    data_ = src.data_;
     return *this;
   }
   AssignSlow(src);
@@ -949,8 +924,8 @@ inline Cord::InlineRep& Cord::InlineRep::operator=(
   if (is_tree()) {
     ClearSlow();
   }
-  memcpy(data_, src.data_, sizeof(data_));
-  memset(src.data_, 0, sizeof(data_));
+  data_ = src.data_;
+  src.ResetToEmpty();
   return *this;
 }
 
@@ -959,43 +934,39 @@ inline void Cord::InlineRep::Swap(Cord::InlineRep* rhs) {
     return;
   }
 
-  Cord::InlineRep tmp;
-  cord_internal::SmallMemmove(tmp.data_, data_, sizeof(data_));
-  cord_internal::SmallMemmove(data_, rhs->data_, sizeof(data_));
-  cord_internal::SmallMemmove(rhs->data_, tmp.data_, sizeof(data_));
+  std::swap(data_, rhs->data_);
 }
 
 inline const char* Cord::InlineRep::data() const {
-  return is_tree() ? nullptr : data_;
+  return is_tree() ? nullptr : data_.as_chars;
 }
 
 inline absl::cord_internal::CordRep* Cord::InlineRep::tree() const {
   if (is_tree()) {
-    absl::cord_internal::CordRep* rep;
-    memcpy(&rep, data_, sizeof(rep));
-    return rep;
+    return data_.as_tree.rep;
   } else {
     return nullptr;
   }
 }
 
-inline bool Cord::InlineRep::empty() const { return data_[kMaxInline] == 0; }
+inline bool Cord::InlineRep::empty() const { return tagged_size() == 0; }
 
 inline size_t Cord::InlineRep::size() const {
-  const char tag = data_[kMaxInline];
+  const char tag = tagged_size();
   if (tag <= kMaxInline) return tag;
   return static_cast<size_t>(tree()->length);
 }
 
 inline void Cord::InlineRep::set_tree(absl::cord_internal::CordRep* rep) {
   if (rep == nullptr) {
-    memset(data_, 0, sizeof(data_));
+    ResetToEmpty();
   } else {
     bool was_tree = is_tree();
-    memcpy(data_, &rep, sizeof(rep));
-    memset(data_ + sizeof(rep), 0, sizeof(data_) - sizeof(rep) - 1);
+    data_.as_tree = {rep, {}, tagged_size()};
     if (!was_tree) {
-      data_[kMaxInline] = kTreeFlag;
+      // If we were not a tree already, set the tag.
+      // Otherwise, leave it alone because it might have the profile bit on.
+      set_tagged_size(kTreeFlag);
     }
   }
 }
@@ -1006,29 +977,36 @@ inline void Cord::InlineRep::replace_tree(absl::cord_internal::CordRep* rep) {
     set_tree(rep);
     return;
   }
-  memcpy(data_, &rep, sizeof(rep));
-  memset(data_ + sizeof(rep), 0, sizeof(data_) - sizeof(rep) - 1);
+  data_.as_tree = {rep, {}, tagged_size()};
 }
 
 inline absl::cord_internal::CordRep* Cord::InlineRep::clear() {
-  const char tag = data_[kMaxInline];
-  absl::cord_internal::CordRep* result = nullptr;
-  if (tag > kMaxInline) {
-    memcpy(&result, data_, sizeof(result));
-  }
-  memset(data_, 0, sizeof(data_));  // Clear the cord
+  absl::cord_internal::CordRep* result = tree();
+  ResetToEmpty();
   return result;
 }
 
 inline void Cord::InlineRep::CopyToArray(char* dst) const {
   assert(!is_tree());
-  size_t n = data_[kMaxInline];
+  size_t n = tagged_size();
   assert(n != 0);
-  cord_internal::SmallMemmove(dst, data_, n);
+  cord_internal::SmallMemmove(dst, data_.as_chars, n);
 }
 
 constexpr inline Cord::Cord() noexcept {}
 
+template <typename T>
+constexpr Cord::Cord(strings_internal::StringConstant<T>)
+    : contents_(strings_internal::StringConstant<T>::value.size() <=
+                        cord_internal::kMaxInline
+                    ? cord_internal::InlineData(
+                          strings_internal::StringConstant<T>::value)
+                    : cord_internal::InlineData(cord_internal::AsTree{
+                          &cord_internal::ConstInitExternalStorage<
+                              strings_internal::StringConstant<T>>::value,
+                          {},
+                          cord_internal::kTreeFlag})) {}
+
 inline Cord& Cord::operator=(const Cord& x) {
   contents_ = x.contents_;
   return *this;
diff --git a/third_party/abseil_cpp/absl/strings/cord_test.cc b/third_party/abseil_cpp/absl/strings/cord_test.cc
index 4443c8289658..7942bfc03c49 100644
--- a/third_party/abseil_cpp/absl/strings/cord_test.cc
+++ b/third_party/abseil_cpp/absl/strings/cord_test.cc
@@ -1,3 +1,17 @@
+// Copyright 2020 The Abseil Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
 #include "absl/strings/cord.h"
 
 #include <algorithm>
@@ -167,6 +181,8 @@ class CordTestPeer {
       const Cord& c, absl::FunctionRef<void(absl::string_view)> callback) {
     c.ForEachChunk(callback);
   }
+
+  static bool IsTree(const Cord& c) { return c.contents_.is_tree(); }
 };
 
 ABSL_NAMESPACE_END
@@ -1613,3 +1629,83 @@ TEST(CordDeathTest, Hardening) {
   EXPECT_DEATH_IF_SUPPORTED(static_cast<void>(cord.chunk_end()->empty()), "");
   EXPECT_DEATH_IF_SUPPORTED(++cord.chunk_end(), "");
 }
+
+class AfterExitCordTester {
+ public:
+  bool Set(absl::Cord* cord, absl::string_view expected) {
+    cord_ = cord;
+    expected_ = expected;
+    return true;
+  }
+
+  ~AfterExitCordTester() {
+    EXPECT_EQ(*cord_, expected_);
+  }
+ private:
+  absl::Cord* cord_;
+  absl::string_view expected_;
+};
+
+template <typename Str>
+void TestConstinitConstructor(Str) {
+  const auto expected = Str::value;
+  // Defined before `cord` to be destroyed after it.
+  static AfterExitCordTester exit_tester;  // NOLINT
+  ABSL_CONST_INIT static absl::Cord cord(Str{});  // NOLINT
+  static bool init_exit_tester = exit_tester.Set(&cord, expected);
+  (void)init_exit_tester;
+
+  EXPECT_EQ(cord, expected);
+  // Copy the object and test the copy, and the original.
+  {
+    absl::Cord copy = cord;
+    EXPECT_EQ(copy, expected);
+  }
+  // The original still works
+  EXPECT_EQ(cord, expected);
+
+  // Try making adding more structure to the tree.
+  {
+    absl::Cord copy = cord;
+    std::string expected_copy(expected);
+    for (int i = 0; i < 10; ++i) {
+      copy.Append(cord);
+      absl::StrAppend(&expected_copy, expected);
+      EXPECT_EQ(copy, expected_copy);
+    }
+  }
+
+  // Make sure we are using the right branch during constant evaluation.
+  EXPECT_EQ(absl::CordTestPeer::IsTree(cord), cord.size() >= 16);
+
+  for (int i = 0; i < 10; ++i) {
+    // Make a few more Cords from the same global rep.
+    // This tests what happens when the refcount for it gets below 1.
+    EXPECT_EQ(expected, absl::Cord(Str{}));
+  }
+}
+
+constexpr int SimpleStrlen(const char* p) {
+  return *p ? 1 + SimpleStrlen(p + 1) : 0;
+}
+
+struct ShortView {
+  constexpr absl::string_view operator()() const {
+    return absl::string_view("SSO string", SimpleStrlen("SSO string"));
+  }
+};
+
+struct LongView {
+  constexpr absl::string_view operator()() const {
+    return absl::string_view("String that does not fit SSO.",
+                             SimpleStrlen("String that does not fit SSO."));
+  }
+};
+
+
+TEST(Cord, ConstinitConstructor) {
+  TestConstinitConstructor(
+      absl::strings_internal::MakeStringConstant(ShortView{}));
+  TestConstinitConstructor(
+      absl::strings_internal::MakeStringConstant(LongView{}));
+}
diff --git a/third_party/abseil_cpp/absl/strings/escaping.cc b/third_party/abseil_cpp/absl/strings/escaping.cc
index 9fceeef0bc95..18b20b83fd36 100644
--- a/third_party/abseil_cpp/absl/strings/escaping.cc
+++ b/third_party/abseil_cpp/absl/strings/escaping.cc
@@ -137,7 +137,7 @@ bool CUnescapeInternal(absl::string_view source, bool leave_nulls_escaped,
             // Copy the escape sequence for the null character
             const ptrdiff_t octal_size = p + 1 - octal_start;
             *d++ = '\\';
-            memcpy(d, octal_start, octal_size);
+            memmove(d, octal_start, octal_size);
             d += octal_size;
             break;
           }
@@ -170,7 +170,7 @@ bool CUnescapeInternal(absl::string_view source, bool leave_nulls_escaped,
             // Copy the escape sequence for the null character
             const ptrdiff_t hex_size = p + 1 - hex_start;
             *d++ = '\\';
-            memcpy(d, hex_start, hex_size);
+            memmove(d, hex_start, hex_size);
             d += hex_size;
             break;
           }
@@ -203,7 +203,7 @@ bool CUnescapeInternal(absl::string_view source, bool leave_nulls_escaped,
           if ((rune == 0) && leave_nulls_escaped) {
             // Copy the escape sequence for the null character
             *d++ = '\\';
-            memcpy(d, hex_start, 5);  // u0000
+            memmove(d, hex_start, 5);  // u0000
             d += 5;
             break;
           }
@@ -251,7 +251,7 @@ bool CUnescapeInternal(absl::string_view source, bool leave_nulls_escaped,
           if ((rune == 0) && leave_nulls_escaped) {
             // Copy the escape sequence for the null character
             *d++ = '\\';
-            memcpy(d, hex_start, 9);  // U00000000
+            memmove(d, hex_start, 9);  // U00000000
             d += 9;
             break;
           }
diff --git a/third_party/abseil_cpp/absl/strings/internal/charconv_bigint_test.cc b/third_party/abseil_cpp/absl/strings/internal/charconv_bigint_test.cc
index 363bcb03d938..a8b9945829e8 100644
--- a/third_party/abseil_cpp/absl/strings/internal/charconv_bigint_test.cc
+++ b/third_party/abseil_cpp/absl/strings/internal/charconv_bigint_test.cc
@@ -69,6 +69,61 @@ TEST(BigUnsigned, ShiftLeft) {
     // And we should have fully rotated all bits off by now:
     EXPECT_EQ(a, BigUnsigned<84>(0u));
   }
+  {
+    // Bit shifting large and small numbers by large and small offsets.
+    // Intended to exercise bounds-checking corner on ShiftLeft() (directly
+    // and under asan).
+
+    // 2**(32*84)-1
+    const BigUnsigned<84> all_bits_one(
+        "1474444211396924248063325089479706787923460402125687709454567433186613"
+        "6228083464060749874845919674257665016359189106695900028098437021384227"
+        "3285029708032466536084583113729486015826557532750465299832071590813090"
+        "2011853039837649252477307070509704043541368002938784757296893793903797"
+        "8180292336310543540677175225040919704702800559606097685920595947397024"
+        "8303316808753252115729411497720357971050627997031988036134171378490368"
+        "6008000778741115399296162550786288457245180872759047016734959330367829"
+        "5235612397427686310674725251378116268607113017720538636924549612987647"
+        "5767411074510311386444547332882472126067840027882117834454260409440463"
+        "9345147252664893456053258463203120637089916304618696601333953616715125"
+        "2115882482473279040772264257431663818610405673876655957323083702713344"
+        "4201105427930770976052393421467136557055");
+    const BigUnsigned<84> zero(0u);
+    const BigUnsigned<84> one(1u);
+    // in bounds shifts
+    for (int i = 1; i < 84*32; ++i) {
+      // shifting all_bits_one to the left should result in a smaller number,
+      // since the high bits rotate off and the low bits are replaced with
+      // zeroes.
+      BigUnsigned<84> big_shifted = all_bits_one;
+      big_shifted.ShiftLeft(i);
+      EXPECT_GT(all_bits_one, big_shifted);
+      // Shifting 1 to the left should instead result in a larger number.
+      BigUnsigned<84> small_shifted = one;
+      small_shifted.ShiftLeft(i);
+      EXPECT_LT(one, small_shifted);
+    }
+    // Shifting by zero or a negative number has no effect
+    for (int no_op_shift : {0, -1, -84 * 32, std::numeric_limits<int>::min()}) {
+      BigUnsigned<84> big_shifted = all_bits_one;
+      big_shifted.ShiftLeft(no_op_shift);
+      EXPECT_EQ(all_bits_one, big_shifted);
+      BigUnsigned<84> small_shifted = one;
+      big_shifted.ShiftLeft(no_op_shift);
+      EXPECT_EQ(one, small_shifted);
+    }
+    // Shifting by an amount greater than the number of bits should result in
+    // zero.
+    for (int out_of_bounds_shift :
+         {84 * 32, 84 * 32 + 1, std::numeric_limits<int>::max()}) {
+      BigUnsigned<84> big_shifted = all_bits_one;
+      big_shifted.ShiftLeft(out_of_bounds_shift);
+      EXPECT_EQ(zero, big_shifted);
+      BigUnsigned<84> small_shifted = one;
+      small_shifted.ShiftLeft(out_of_bounds_shift);
+      EXPECT_EQ(zero, small_shifted);
+    }
+  }
 }
 
 TEST(BigUnsigned, MultiplyByUint32) {
diff --git a/third_party/abseil_cpp/absl/strings/internal/charconv_parse.cc b/third_party/abseil_cpp/absl/strings/internal/charconv_parse.cc
index fd6d9480fc04..8b11868c887a 100644
--- a/third_party/abseil_cpp/absl/strings/internal/charconv_parse.cc
+++ b/third_party/abseil_cpp/absl/strings/internal/charconv_parse.cc
@@ -246,8 +246,8 @@ constexpr int DigitMagnitude<16>() {
 // ConsumeDigits does not protect against overflow on *out; max_digits must
 // be chosen with respect to type T to avoid the possibility of overflow.
 template <int base, typename T>
-std::size_t ConsumeDigits(const char* begin, const char* end, int max_digits,
-                          T* out, bool* dropped_nonzero_digit) {
+int ConsumeDigits(const char* begin, const char* end, int max_digits, T* out,
+                  bool* dropped_nonzero_digit) {
   if (base == 10) {
     assert(max_digits <= std::numeric_limits<T>::digits10);
   } else if (base == 16) {
@@ -282,7 +282,7 @@ std::size_t ConsumeDigits(const char* begin, const char* end, int max_digits,
     *dropped_nonzero_digit = true;
   }
   *out = accumulator;
-  return begin - original_begin;
+  return static_cast<int>(begin - original_begin);
 }
 
 // Returns true if `v` is one of the chars allowed inside parentheses following
@@ -372,7 +372,7 @@ strings_internal::ParsedFloat ParseFloat(const char* begin, const char* end,
 
   int exponent_adjustment = 0;
   bool mantissa_is_inexact = false;
-  std::size_t pre_decimal_digits = ConsumeDigits<base>(
+  int pre_decimal_digits = ConsumeDigits<base>(
       begin, end, MantissaDigitsMax<base>(), &mantissa, &mantissa_is_inexact);
   begin += pre_decimal_digits;
   int digits_left;
@@ -398,14 +398,14 @@ strings_internal::ParsedFloat ParseFloat(const char* begin, const char* end,
       while (begin < end && *begin == '0') {
         ++begin;
       }
-      std::size_t zeros_skipped = begin - begin_zeros;
+      int zeros_skipped = static_cast<int>(begin - begin_zeros);
       if (zeros_skipped >= DigitLimit<base>()) {
         // refuse to parse pathological inputs
         return result;
       }
       exponent_adjustment -= static_cast<int>(zeros_skipped);
     }
-    std::size_t post_decimal_digits = ConsumeDigits<base>(
+    int post_decimal_digits = ConsumeDigits<base>(
         begin, end, digits_left, &mantissa, &mantissa_is_inexact);
     begin += post_decimal_digits;
 
diff --git a/third_party/abseil_cpp/absl/strings/internal/cord_internal.h b/third_party/abseil_cpp/absl/strings/internal/cord_internal.h
index 830ceaf473bd..aa91a691b949 100644
--- a/third_party/abseil_cpp/absl/strings/internal/cord_internal.h
+++ b/third_party/abseil_cpp/absl/strings/internal/cord_internal.h
@@ -21,6 +21,8 @@
 #include <cstdint>
 #include <type_traits>
 
+#include "absl/base/internal/invoke.h"
+#include "absl/container/internal/compressed_tuple.h"
 #include "absl/meta/type_traits.h"
 #include "absl/strings/string_view.h"
 
@@ -31,14 +33,17 @@ namespace cord_internal {
 // Wraps std::atomic for reference counting.
 class Refcount {
  public:
-  Refcount() : count_{1} {}
-  ~Refcount() {}
+  constexpr Refcount() : count_{kRefIncrement} {}
+  struct Immortal {};
+  explicit constexpr Refcount(Immortal) : count_(kImmortalTag) {}
 
-  // Increments the reference count by 1. Imposes no memory ordering.
-  inline void Increment() { count_.fetch_add(1, std::memory_order_relaxed); }
+  // Increments the reference count. Imposes no memory ordering.
+  inline void Increment() {
+    count_.fetch_add(kRefIncrement, std::memory_order_relaxed);
+  }
 
   // Asserts that the current refcount is greater than 0. If the refcount is
-  // greater than 1, decrements the reference count by 1.
+  // greater than 1, decrements the reference count.
   //
   // Returns false if there are no references outstanding; true otherwise.
   // Inserts barriers to ensure that state written before this method returns
@@ -46,19 +51,24 @@ class Refcount {
   // false.
   inline bool Decrement() {
     int32_t refcount = count_.load(std::memory_order_acquire);
-    assert(refcount > 0);
-    return refcount != 1 && count_.fetch_sub(1, std::memory_order_acq_rel) != 1;
+    assert(refcount > 0 || refcount & kImmortalTag);
+    return refcount != kRefIncrement &&
+           count_.fetch_sub(kRefIncrement, std::memory_order_acq_rel) !=
+               kRefIncrement;
   }
 
   // Same as Decrement but expect that refcount is greater than 1.
   inline bool DecrementExpectHighRefcount() {
-    int32_t refcount = count_.fetch_sub(1, std::memory_order_acq_rel);
-    assert(refcount > 0);
-    return refcount != 1;
+    int32_t refcount =
+        count_.fetch_sub(kRefIncrement, std::memory_order_acq_rel);
+    assert(refcount > 0 || refcount & kImmortalTag);
+    return refcount != kRefIncrement;
   }
 
   // Returns the current reference count using acquire semantics.
-  inline int32_t Get() const { return count_.load(std::memory_order_acquire); }
+  inline int32_t Get() const {
+    return count_.load(std::memory_order_acquire) >> kImmortalShift;
+  }
 
   // Returns whether the atomic integer is 1.
   // If the reference count is used in the conventional way, a
@@ -68,9 +78,27 @@ class Refcount {
   // performs the memory barrier needed for the owning thread
   // to act on the object, knowing that it has exclusive access to the
   // object.
-  inline bool IsOne() { return count_.load(std::memory_order_acquire) == 1; }
+  inline bool IsOne() {
+    return count_.load(std::memory_order_acquire) == kRefIncrement;
+  }
+
+  bool IsImmortal() const {
+    return (count_.load(std::memory_order_relaxed) & kImmortalTag) != 0;
+  }
 
  private:
+  // We reserve the bottom bit to tag a reference count as immortal.
+  // By making it `1` we ensure that we never reach `0` when adding/subtracting
+  // `2`, thus it never looks as if it should be destroyed.
+  // These are used for the StringConstant constructor where we do not increase
+  // the refcount at construction time (due to constinit requirements) but we
+  // will still decrease it at destruction time to avoid branching on Unref.
+  enum {
+    kImmortalShift = 1,
+    kRefIncrement = 1 << kImmortalShift,
+    kImmortalTag = kRefIncrement - 1
+  };
+
   std::atomic<int32_t> count_;
 };
 
@@ -83,7 +111,22 @@ struct CordRepConcat;
 struct CordRepSubstring;
 struct CordRepExternal;
 
+// Various representations that we allow
+enum CordRepKind {
+  CONCAT        = 0,
+  EXTERNAL      = 1,
+  SUBSTRING     = 2,
+
+  // We have different tags for different sized flat arrays,
+  // starting with FLAT
+  FLAT          = 3,
+};
+
 struct CordRep {
+  CordRep() = default;
+  constexpr CordRep(Refcount::Immortal immortal, size_t l)
+      : length(l), refcount(immortal), tag(EXTERNAL), data{} {}
+
   // The following three fields have to be less than 32 bytes since
   // that is the smallest supported flat node size.
   size_t length;
@@ -114,35 +157,112 @@ struct CordRepSubstring : public CordRep {
   CordRep* child;
 };
 
-// TODO(strel): replace the following logic (and related functions in cord.cc)
-// with container_internal::Layout.
-
-// Alignment requirement for CordRepExternal so that the type erased releaser
-// will be stored at a suitably aligned address.
-constexpr size_t ExternalRepAlignment() {
-#if defined(__STDCPP_DEFAULT_NEW_ALIGNMENT__)
-  return __STDCPP_DEFAULT_NEW_ALIGNMENT__;
-#else
-  return alignof(max_align_t);
-#endif
-}
-
-// Type for function pointer that will invoke and destroy the type-erased
-// releaser function object. Accepts a pointer to the releaser and the
-// `string_view` that were passed in to `NewExternalRep` below. The return value
-// is the size of the `Releaser` type.
-using ExternalReleaserInvoker = size_t (*)(void*, absl::string_view);
+// Type for function pointer that will invoke the releaser function and also
+// delete the `CordRepExternalImpl` corresponding to the passed in
+// `CordRepExternal`.
+using ExternalReleaserInvoker = void (*)(CordRepExternal*);
 
 // External CordReps are allocated together with a type erased releaser. The
 // releaser is stored in the memory directly following the CordRepExternal.
-struct alignas(ExternalRepAlignment()) CordRepExternal : public CordRep {
+struct CordRepExternal : public CordRep {
+  CordRepExternal() = default;
+  explicit constexpr CordRepExternal(absl::string_view str)
+      : CordRep(Refcount::Immortal{}, str.size()),
+        base(str.data()),
+        releaser_invoker(nullptr) {}
+
   const char* base;
   // Pointer to function that knows how to call and destroy the releaser.
   ExternalReleaserInvoker releaser_invoker;
 };
 
-// TODO(strel): look into removing, it doesn't seem like anything relies on this
-static_assert(sizeof(CordRepConcat) == sizeof(CordRepSubstring), "");
+struct Rank1 {};
+struct Rank0 : Rank1 {};
+
+template <typename Releaser, typename = ::absl::base_internal::invoke_result_t<
+                                 Releaser, absl::string_view>>
+void InvokeReleaser(Rank0, Releaser&& releaser, absl::string_view data) {
+  ::absl::base_internal::invoke(std::forward<Releaser>(releaser), data);
+}
+
+template <typename Releaser,
+          typename = ::absl::base_internal::invoke_result_t<Releaser>>
+void InvokeReleaser(Rank1, Releaser&& releaser, absl::string_view) {
+  ::absl::base_internal::invoke(std::forward<Releaser>(releaser));
+}
+
+// We use CompressedTuple so that we can benefit from EBCO.
+template <typename Releaser>
+struct CordRepExternalImpl
+    : public CordRepExternal,
+      public ::absl::container_internal::CompressedTuple<Releaser> {
+  // The extra int arg is so that we can avoid interfering with copy/move
+  // constructors while still benefitting from perfect forwarding.
+  template <typename T>
+  CordRepExternalImpl(T&& releaser, int)
+      : CordRepExternalImpl::CompressedTuple(std::forward<T>(releaser)) {
+    this->releaser_invoker = &Release;
+  }
+
+  ~CordRepExternalImpl() {
+    InvokeReleaser(Rank0{}, std::move(this->template get<0>()),
+                   absl::string_view(base, length));
+  }
+
+  static void Release(CordRepExternal* rep) {
+    delete static_cast<CordRepExternalImpl*>(rep);
+  }
+};
+
+template <typename Str>
+struct ConstInitExternalStorage {
+  ABSL_CONST_INIT static CordRepExternal value;
+};
+
+template <typename Str>
+CordRepExternal ConstInitExternalStorage<Str>::value(Str::value);
+
+enum {
+  kMaxInline = 15,
+  // Tag byte & kMaxInline means we are storing a pointer.
+  kTreeFlag = 1 << 4,
+  // Tag byte & kProfiledFlag means we are profiling the Cord.
+  kProfiledFlag = 1 << 5
+};
+
+// If the data has length <= kMaxInline, we store it in `as_chars`, and
+// store the size in `tagged_size`.
+// Else we store it in a tree and store a pointer to that tree in
+// `as_tree.rep` and store a tag in `tagged_size`.
+struct AsTree {
+  absl::cord_internal::CordRep* rep;
+  char padding[kMaxInline + 1 - sizeof(absl::cord_internal::CordRep*) - 1];
+  char tagged_size;
+};
+
+constexpr char GetOrNull(absl::string_view data, size_t pos) {
+  return pos < data.size() ? data[pos] : '\0';
+}
+
+union InlineData {
+  constexpr InlineData() : as_chars{} {}
+  explicit constexpr InlineData(AsTree tree) : as_tree(tree) {}
+  explicit constexpr InlineData(absl::string_view chars)
+      : as_chars{GetOrNull(chars, 0),  GetOrNull(chars, 1),
+                 GetOrNull(chars, 2),  GetOrNull(chars, 3),
+                 GetOrNull(chars, 4),  GetOrNull(chars, 5),
+                 GetOrNull(chars, 6),  GetOrNull(chars, 7),
+                 GetOrNull(chars, 8),  GetOrNull(chars, 9),
+                 GetOrNull(chars, 10), GetOrNull(chars, 11),
+                 GetOrNull(chars, 12), GetOrNull(chars, 13),
+                 GetOrNull(chars, 14), static_cast<char>(chars.size())} {}
+
+  AsTree as_tree;
+  char as_chars[kMaxInline + 1];
+};
+static_assert(sizeof(InlineData) == kMaxInline + 1, "");
+static_assert(sizeof(AsTree) == sizeof(InlineData), "");
+static_assert(offsetof(AsTree, tagged_size) == kMaxInline, "");
 
 }  // namespace cord_internal
 ABSL_NAMESPACE_END
diff --git a/third_party/abseil_cpp/absl/strings/internal/str_format/arg.cc b/third_party/abseil_cpp/absl/strings/internal/str_format/arg.cc
index 9feb22487932..e28a29b17169 100644
--- a/third_party/abseil_cpp/absl/strings/internal/str_format/arg.cc
+++ b/third_party/abseil_cpp/absl/strings/internal/str_format/arg.cc
@@ -1,3 +1,17 @@
+// Copyright 2020 The Abseil Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
 //
 // POSIX spec:
 //   http://pubs.opengroup.org/onlinepubs/009695399/functions/fprintf.html
diff --git a/third_party/abseil_cpp/absl/strings/internal/str_format/arg.h b/third_party/abseil_cpp/absl/strings/internal/str_format/arg.h
index d441e87fff33..7040c866778e 100644
--- a/third_party/abseil_cpp/absl/strings/internal/str_format/arg.h
+++ b/third_party/abseil_cpp/absl/strings/internal/str_format/arg.h
@@ -1,3 +1,17 @@
+// Copyright 2020 The Abseil Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
 #ifndef ABSL_STRINGS_INTERNAL_STR_FORMAT_ARG_H_
 #define ABSL_STRINGS_INTERNAL_STR_FORMAT_ARG_H_
 
@@ -25,10 +39,12 @@ class Cord;
 class FormatCountCapture;
 class FormatSink;
 
-namespace str_format_internal {
-
+template <absl::FormatConversionCharSet C>
+struct FormatConvertResult;
 class FormatConversionSpec;
 
+namespace str_format_internal {
+
 template <typename T, typename = void>
 struct HasUserDefinedConvert : std::false_type {};
 
@@ -39,6 +55,22 @@ struct HasUserDefinedConvert<T, void_t<decltype(AbslFormatConvert(
                                     std::declval<FormatSink*>()))>>
     : std::true_type {};
 
+void AbslFormatConvert();  // Stops the lexical name lookup
+template <typename T>
+auto FormatConvertImpl(const T& v, FormatConversionSpecImpl conv,
+                       FormatSinkImpl* sink)
+    -> decltype(AbslFormatConvert(v,
+                                  std::declval<const FormatConversionSpec&>(),
+                                  std::declval<FormatSink*>())) {
+  using FormatConversionSpecT =
+      absl::enable_if_t<sizeof(const T& (*)()) != 0, FormatConversionSpec>;
+  using FormatSinkT =
+      absl::enable_if_t<sizeof(const T& (*)()) != 0, FormatSink>;
+  auto fcs = conv.Wrap<FormatConversionSpecT>();
+  auto fs = sink->Wrap<FormatSinkT>();
+  return AbslFormatConvert(v, fcs, &fs);
+}
+
 template <typename T>
 class StreamedWrapper;
 
@@ -46,6 +78,13 @@ class StreamedWrapper;
 // then convert it, appending to `sink` and return `true`.
 // Otherwise fail and return `false`.
 
+// AbslFormatConvert(v, conv, sink) is intended to be found by ADL on 'v'
+// as an extension mechanism. These FormatConvertImpl functions are the default
+// implementations.
+// The ADL search is augmented via the 'Sink*' parameter, which also
+// serves as a disambiguator to reject possible unintended 'AbslFormatConvert'
+// functions in the namespaces associated with 'v'.
+
 // Raw pointers.
 struct VoidPtr {
   VoidPtr() = default;
@@ -62,6 +101,11 @@ struct ArgConvertResult {
 };
 
 template <FormatConversionCharSet C>
+constexpr FormatConversionCharSet ExtractCharSet(FormatConvertResult<C>) {
+  return C;
+}
+
+template <FormatConversionCharSet C>
 constexpr FormatConversionCharSet ExtractCharSet(ArgConvertResult<C>) {
   return C;
 }
diff --git a/third_party/abseil_cpp/absl/strings/internal/str_format/arg_test.cc b/third_party/abseil_cpp/absl/strings/internal/str_format/arg_test.cc
index bf3d7e8e3777..1261937c3097 100644
--- a/third_party/abseil_cpp/absl/strings/internal/str_format/arg_test.cc
+++ b/third_party/abseil_cpp/absl/strings/internal/str_format/arg_test.cc
@@ -6,6 +6,12 @@
 //
 //      https://www.apache.org/licenses/LICENSE-2.0
 //
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
 #include "absl/strings/internal/str_format/arg.h"
 
 #include <ostream>
@@ -23,8 +29,17 @@ class FormatArgImplTest : public ::testing::Test {
   enum Color { kRed, kGreen, kBlue };
 
   static const char *hi() { return "hi"; }
+
+  struct X {};
+
+  X x_;
 };
 
+inline FormatConvertResult<FormatConversionCharSet{}> AbslFormatConvert(
+    const FormatArgImplTest::X &, const FormatConversionSpec &, FormatSink *) {
+  return {false};
+}
+
 TEST_F(FormatArgImplTest, ToInt) {
   int out = 0;
   EXPECT_TRUE(FormatArgImplFriend::ToInt(FormatArgImpl(1), &out));
@@ -59,6 +74,7 @@ TEST_F(FormatArgImplTest, ToInt) {
       FormatArgImpl(static_cast<int *>(nullptr)), &out));
   EXPECT_FALSE(FormatArgImplFriend::ToInt(FormatArgImpl(hi()), &out));
   EXPECT_FALSE(FormatArgImplFriend::ToInt(FormatArgImpl("hi"), &out));
+  EXPECT_FALSE(FormatArgImplFriend::ToInt(FormatArgImpl(x_), &out));
   EXPECT_TRUE(FormatArgImplFriend::ToInt(FormatArgImpl(kBlue), &out));
   EXPECT_EQ(2, out);
 }
diff --git a/third_party/abseil_cpp/absl/strings/internal/str_format/bind.cc b/third_party/abseil_cpp/absl/strings/internal/str_format/bind.cc
index 6980ed1d8f0e..4e68b90b5ce8 100644
--- a/third_party/abseil_cpp/absl/strings/internal/str_format/bind.cc
+++ b/third_party/abseil_cpp/absl/strings/internal/str_format/bind.cc
@@ -1,3 +1,17 @@
+// Copyright 2020 The Abseil Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
 #include "absl/strings/internal/str_format/bind.h"
 
 #include <cerrno>
@@ -221,7 +235,7 @@ int FprintF(std::FILE* output, const UntypedFormatSpecImpl format,
     errno = sink.error();
     return -1;
   }
-  if (sink.count() > std::numeric_limits<int>::max()) {
+  if (sink.count() > static_cast<size_t>(std::numeric_limits<int>::max())) {
     errno = EFBIG;
     return -1;
   }
diff --git a/third_party/abseil_cpp/absl/strings/internal/str_format/bind.h b/third_party/abseil_cpp/absl/strings/internal/str_format/bind.h
index 585246e77e56..267cc0ef6928 100644
--- a/third_party/abseil_cpp/absl/strings/internal/str_format/bind.h
+++ b/third_party/abseil_cpp/absl/strings/internal/str_format/bind.h
@@ -1,3 +1,17 @@
+// Copyright 2020 The Abseil Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
 #ifndef ABSL_STRINGS_INTERNAL_STR_FORMAT_BIND_H_
 #define ABSL_STRINGS_INTERNAL_STR_FORMAT_BIND_H_
 
@@ -119,10 +133,11 @@ class FormatSpecTemplate
 
 #endif  // ABSL_INTERNAL_ENABLE_FORMAT_CHECKER
 
-  template <FormatConversionCharSet... C,
-            typename = typename std::enable_if<
-                AllOf(sizeof...(C) == sizeof...(Args), Contains(Args,
-                                                                C)...)>::type>
+  template <
+      FormatConversionCharSet... C,
+      typename = typename std::enable_if<sizeof...(C) == sizeof...(Args)>::type,
+      typename = typename std::enable_if<AllOf(Contains(Args,
+                                                        C)...)>::type>
   FormatSpecTemplate(const ExtendedParsedFormat<C...>& pc)  // NOLINT
       : Base(&pc) {}
 };
diff --git a/third_party/abseil_cpp/absl/strings/internal/str_format/bind_test.cc b/third_party/abseil_cpp/absl/strings/internal/str_format/bind_test.cc
index 64790a85fd23..1eef9c4326e2 100644
--- a/third_party/abseil_cpp/absl/strings/internal/str_format/bind_test.cc
+++ b/third_party/abseil_cpp/absl/strings/internal/str_format/bind_test.cc
@@ -1,3 +1,17 @@
+// Copyright 2020 The Abseil Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
 #include "absl/strings/internal/str_format/bind.h"
 
 #include <string.h>
diff --git a/third_party/abseil_cpp/absl/strings/internal/str_format/checker.h b/third_party/abseil_cpp/absl/strings/internal/str_format/checker.h
index 424c51f74f17..2a2601eccfd8 100644
--- a/third_party/abseil_cpp/absl/strings/internal/str_format/checker.h
+++ b/third_party/abseil_cpp/absl/strings/internal/str_format/checker.h
@@ -1,3 +1,17 @@
+// Copyright 2020 The Abseil Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
 #ifndef ABSL_STRINGS_INTERNAL_STR_FORMAT_CHECKER_H_
 #define ABSL_STRINGS_INTERNAL_STR_FORMAT_CHECKER_H_
 
diff --git a/third_party/abseil_cpp/absl/strings/internal/str_format/checker_test.cc b/third_party/abseil_cpp/absl/strings/internal/str_format/checker_test.cc
index a76d70b0586c..7c70f47d682a 100644
--- a/third_party/abseil_cpp/absl/strings/internal/str_format/checker_test.cc
+++ b/third_party/abseil_cpp/absl/strings/internal/str_format/checker_test.cc
@@ -1,3 +1,17 @@
+// Copyright 2020 The Abseil Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
 #include <string>
 
 #include "gmock/gmock.h"
diff --git a/third_party/abseil_cpp/absl/strings/internal/str_format/convert_test.cc b/third_party/abseil_cpp/absl/strings/internal/str_format/convert_test.cc
index 0e8535c27b7a..375db0a0592c 100644
--- a/third_party/abseil_cpp/absl/strings/internal/str_format/convert_test.cc
+++ b/third_party/abseil_cpp/absl/strings/internal/str_format/convert_test.cc
@@ -1,3 +1,17 @@
+// Copyright 2020 The Abseil Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
 #include <errno.h>
 #include <stdarg.h>
 #include <stdio.h>
@@ -12,6 +26,7 @@
 #include "gtest/gtest.h"
 #include "absl/base/internal/raw_logging.h"
 #include "absl/strings/internal/str_format/bind.h"
+#include "absl/strings/match.h"
 #include "absl/types/optional.h"
 
 namespace absl {
@@ -19,6 +34,13 @@ ABSL_NAMESPACE_BEGIN
 namespace str_format_internal {
 namespace {
 
+struct NativePrintfTraits {
+  bool hex_float_has_glibc_rounding;
+  bool hex_float_prefers_denormal_repr;
+  bool hex_float_uses_minimal_precision_when_not_specified;
+  bool hex_float_optimizes_leading_digit_bit_count;
+};
+
 template <typename T, size_t N>
 size_t ArraySize(T (&)[N]) {
   return N;
@@ -118,6 +140,63 @@ std::string StrPrint(const char *format, ...) {
   return result;
 }
 
+NativePrintfTraits VerifyNativeImplementationImpl() {
+  NativePrintfTraits result;
+
+  // >>> hex_float_has_glibc_rounding. To have glibc's rounding behavior we need
+  // to meet three requirements:
+  //
+  //   - The threshold for rounding up is 8 (for e.g. MSVC uses 9).
+  //   - If the digits lower than than the 8 are non-zero then we round up.
+  //   - If the digits lower than the 8 are all zero then we round toward even.
+  //
+  // The numbers below represent all the cases covering {below,at,above} the
+  // threshold (8) with both {zero,non-zero} lower bits and both {even,odd}
+  // preceding digits.
+  const double d0079 = 65657.0;  // 0x1.0079p+16
+  const double d0179 = 65913.0;  // 0x1.0179p+16
+  const double d0080 = 65664.0;  // 0x1.0080p+16
+  const double d0180 = 65920.0;  // 0x1.0180p+16
+  const double d0081 = 65665.0;  // 0x1.0081p+16
+  const double d0181 = 65921.0;  // 0x1.0181p+16
+  result.hex_float_has_glibc_rounding =
+      StartsWith(StrPrint("%.2a", d0079), "0x1.00") &&
+      StartsWith(StrPrint("%.2a", d0179), "0x1.01") &&
+      StartsWith(StrPrint("%.2a", d0080), "0x1.00") &&
+      StartsWith(StrPrint("%.2a", d0180), "0x1.02") &&
+      StartsWith(StrPrint("%.2a", d0081), "0x1.01") &&
+      StartsWith(StrPrint("%.2a", d0181), "0x1.02");
+
+  // >>> hex_float_prefers_denormal_repr. Formatting `denormal` on glibc yields
+  // "0x0.0000000000001p-1022", whereas on std libs that don't use denormal
+  // representation it would either be 0x1p-1074 or 0x1.0000000000000-1074.
+  const double denormal = std::numeric_limits<double>::denorm_min();
+  result.hex_float_prefers_denormal_repr =
+      StartsWith(StrPrint("%a", denormal), "0x0.0000000000001");
+
+  // >>> hex_float_uses_minimal_precision_when_not_specified. Some (non-glibc)
+  // libs will format the following as "0x1.0079000000000p+16".
+  result.hex_float_uses_minimal_precision_when_not_specified =
+      (StrPrint("%a", d0079) == "0x1.0079p+16");
+
+  // >>> hex_float_optimizes_leading_digit_bit_count. The number 1.5, when
+  // formatted by glibc should yield "0x1.8p+0" for `double` and "0xcp-3" for
+  // `long double`, i.e., number of bits in the leading digit is adapted to the
+  // number of bits in the mantissa.
+  const double d_15 = 1.5;
+  const long double ld_15 = 1.5;
+  result.hex_float_optimizes_leading_digit_bit_count =
+      StartsWith(StrPrint("%a", d_15), "0x1.8") &&
+      StartsWith(StrPrint("%La", ld_15), "0xc");
+
+  return result;
+}
+
+const NativePrintfTraits &VerifyNativeImplementation() {
+  static NativePrintfTraits native_traits = VerifyNativeImplementationImpl();
+  return native_traits;
+}
+
 class FormatConvertTest : public ::testing::Test { };
 
 template <typename T>
@@ -474,6 +553,68 @@ TEST_F(FormatConvertTest, Uint128) {
   }
 }
 
+template <typename Floating>
+void TestWithMultipleFormatsHelper(const std::vector<Floating> &floats) {
+  const NativePrintfTraits &native_traits = VerifyNativeImplementation();
+  // Reserve the space to ensure we don't allocate memory in the output itself.
+  std::string str_format_result;
+  str_format_result.reserve(1 << 20);
+  std::string string_printf_result;
+  string_printf_result.reserve(1 << 20);
+
+  const char *const kFormats[] = {
+      "%",  "%.3", "%8.5", "%500",   "%.5000", "%.60", "%.30",   "%03",
+      "%+", "% ",  "%-10", "%#15.3", "%#.0",   "%.0",  "%1$*2$", "%1$.*2$"};
+
+  for (const char *fmt : kFormats) {
+    for (char f : {'f', 'F',  //
+                   'g', 'G',  //
+                   'a', 'A',  //
+                   'e', 'E'}) {
+      std::string fmt_str = std::string(fmt) + f;
+
+      if (fmt == absl::string_view("%.5000") && f != 'f' && f != 'F' &&
+          f != 'a' && f != 'A') {
+        // This particular test takes way too long with snprintf.
+        // Disable for the case we are not implementing natively.
+        continue;
+      }
+
+      if ((f == 'a' || f == 'A') &&
+          !native_traits.hex_float_has_glibc_rounding) {
+        continue;
+      }
+
+      for (Floating d : floats) {
+        if (!native_traits.hex_float_prefers_denormal_repr &&
+            (f == 'a' || f == 'A') && std::fpclassify(d) == FP_SUBNORMAL) {
+          continue;
+        }
+        int i = -10;
+        FormatArgImpl args[2] = {FormatArgImpl(d), FormatArgImpl(i)};
+        UntypedFormatSpecImpl format(fmt_str);
+
+        string_printf_result.clear();
+        StrAppend(&string_printf_result, fmt_str.c_str(), d, i);
+        str_format_result.clear();
+
+        {
+          AppendPack(&str_format_result, format, absl::MakeSpan(args));
+        }
+
+        if (string_printf_result != str_format_result) {
+          // We use ASSERT_EQ here because failures are usually correlated and a
+          // bug would print way too many failed expectations causing the test
+          // to time out.
+          ASSERT_EQ(string_printf_result, str_format_result)
+              << fmt_str << " " << StrPrint("%.18g", d) << " "
+              << StrPrint("%a", d) << " " << StrPrint("%.50f", d);
+        }
+      }
+    }
+  }
+}
+
 TEST_F(FormatConvertTest, Float) {
 #ifdef _MSC_VER
   // MSVC has a different rounding policy than us so we can't test our
@@ -481,9 +622,62 @@ TEST_F(FormatConvertTest, Float) {
   return;
 #endif  // _MSC_VER
 
-  const char *const kFormats[] = {
-      "%",  "%.3", "%8.5", "%500",   "%.5000", "%.60", "%.30",   "%03",
-      "%+", "% ",  "%-10", "%#15.3", "%#.0",   "%.0",  "%1$*2$", "%1$.*2$"};
+  std::vector<float> floats = {0.0f,
+                               -0.0f,
+                               .9999999f,
+                               9999999.f,
+                               std::numeric_limits<float>::max(),
+                               -std::numeric_limits<float>::max(),
+                               std::numeric_limits<float>::min(),
+                               -std::numeric_limits<float>::min(),
+                               std::numeric_limits<float>::lowest(),
+                               -std::numeric_limits<float>::lowest(),
+                               std::numeric_limits<float>::epsilon(),
+                               std::numeric_limits<float>::epsilon() + 1.0f,
+                               std::numeric_limits<float>::infinity(),
+                               -std::numeric_limits<float>::infinity()};
+
+  // Some regression tests.
+  floats.push_back(0.999999989f);
+
+  if (std::numeric_limits<float>::has_denorm != std::denorm_absent) {
+    floats.push_back(std::numeric_limits<float>::denorm_min());
+    floats.push_back(-std::numeric_limits<float>::denorm_min());
+  }
+
+  for (float base :
+       {1.f, 12.f, 123.f, 1234.f, 12345.f, 123456.f, 1234567.f, 12345678.f,
+        123456789.f, 1234567890.f, 12345678901.f, 12345678.f, 12345678.f}) {
+    for (int exp = -123; exp <= 123; ++exp) {
+      for (int sign : {1, -1}) {
+        floats.push_back(sign * std::ldexp(base, exp));
+      }
+    }
+  }
+
+  for (int exp = -300; exp <= 300; ++exp) {
+    const float all_ones_mantissa = 0xffffff;
+    floats.push_back(std::ldexp(all_ones_mantissa, exp));
+  }
+
+  // Remove duplicates to speed up the logic below.
+  std::sort(floats.begin(), floats.end());
+  floats.erase(std::unique(floats.begin(), floats.end()), floats.end());
+
+#ifndef __APPLE__
+  // Apple formats NaN differently (+nan) vs. (nan)
+  floats.push_back(std::nan(""));
+#endif
+
+  TestWithMultipleFormatsHelper(floats);
+}
+
+TEST_F(FormatConvertTest, Double) {
+#ifdef _MSC_VER
+  // MSVC has a different rounding policy than us so we can't test our
+  // implementation against the native one there.
+  return;
+#endif  // _MSC_VER
 
   std::vector<double> doubles = {0.0,
                                  -0.0,
@@ -554,52 +748,10 @@ TEST_F(FormatConvertTest, Float) {
   doubles.push_back(std::nan(""));
 #endif
 
-  // Reserve the space to ensure we don't allocate memory in the output itself.
-  std::string str_format_result;
-  str_format_result.reserve(1 << 20);
-  std::string string_printf_result;
-  string_printf_result.reserve(1 << 20);
-
-  for (const char *fmt : kFormats) {
-    for (char f : {'f', 'F',  //
-                   'g', 'G',  //
-                   'a', 'A',  //
-                   'e', 'E'}) {
-      std::string fmt_str = std::string(fmt) + f;
-
-      if (fmt == absl::string_view("%.5000") && f != 'f' && f != 'F') {
-        // This particular test takes way too long with snprintf.
-        // Disable for the case we are not implementing natively.
-        continue;
-      }
-
-      for (double d : doubles) {
-        int i = -10;
-        FormatArgImpl args[2] = {FormatArgImpl(d), FormatArgImpl(i)};
-        UntypedFormatSpecImpl format(fmt_str);
-
-        string_printf_result.clear();
-        StrAppend(&string_printf_result, fmt_str.c_str(), d, i);
-        str_format_result.clear();
-
-        {
-          AppendPack(&str_format_result, format, absl::MakeSpan(args));
-        }
-
-        if (string_printf_result != str_format_result) {
-          // We use ASSERT_EQ here because failures are usually correlated and a
-          // bug would print way too many failed expectations causing the test
-          // to time out.
-          ASSERT_EQ(string_printf_result, str_format_result)
-              << fmt_str << " " << StrPrint("%.18g", d) << " "
-              << StrPrint("%a", d) << " " << StrPrint("%.1080f", d);
-        }
-      }
-    }
-  }
+  TestWithMultipleFormatsHelper(doubles);
 }
 
-TEST_F(FormatConvertTest, FloatRound) {
+TEST_F(FormatConvertTest, DoubleRound) {
   std::string s;
   const auto format = [&](const char *fmt, double d) -> std::string & {
     s.clear();
@@ -704,6 +856,193 @@ TEST_F(FormatConvertTest, FloatRound) {
             "1837869002408041296803276054561138153076171875");
 }
 
+TEST_F(FormatConvertTest, DoubleRoundA) {
+  const NativePrintfTraits &native_traits = VerifyNativeImplementation();
+  std::string s;
+  const auto format = [&](const char *fmt, double d) -> std::string & {
+    s.clear();
+    FormatArgImpl args[1] = {FormatArgImpl(d)};
+    AppendPack(&s, UntypedFormatSpecImpl(fmt), absl::MakeSpan(args));
+    if (native_traits.hex_float_has_glibc_rounding) {
+      EXPECT_EQ(StrPrint(fmt, d), s);
+    }
+    return s;
+  };
+
+  // 0x1.00018000p+100
+  const double on_boundary_odd = 1267679614447900152596896153600.0;
+  EXPECT_EQ(format("%.0a", on_boundary_odd), "0x1p+100");
+  EXPECT_EQ(format("%.1a", on_boundary_odd), "0x1.0p+100");
+  EXPECT_EQ(format("%.2a", on_boundary_odd), "0x1.00p+100");
+  EXPECT_EQ(format("%.3a", on_boundary_odd), "0x1.000p+100");
+  EXPECT_EQ(format("%.4a", on_boundary_odd), "0x1.0002p+100");  // round
+  EXPECT_EQ(format("%.5a", on_boundary_odd), "0x1.00018p+100");
+  EXPECT_EQ(format("%.6a", on_boundary_odd), "0x1.000180p+100");
+
+  // 0x1.00028000p-2
+  const double on_boundary_even = 0.250009536743164062500;
+  EXPECT_EQ(format("%.0a", on_boundary_even), "0x1p-2");
+  EXPECT_EQ(format("%.1a", on_boundary_even), "0x1.0p-2");
+  EXPECT_EQ(format("%.2a", on_boundary_even), "0x1.00p-2");
+  EXPECT_EQ(format("%.3a", on_boundary_even), "0x1.000p-2");
+  EXPECT_EQ(format("%.4a", on_boundary_even), "0x1.0002p-2");  // no round
+  EXPECT_EQ(format("%.5a", on_boundary_even), "0x1.00028p-2");
+  EXPECT_EQ(format("%.6a", on_boundary_even), "0x1.000280p-2");
+
+  // 0x1.00018001p+1
+  const double slightly_over = 2.00004577683284878730773925781250;
+  EXPECT_EQ(format("%.0a", slightly_over), "0x1p+1");
+  EXPECT_EQ(format("%.1a", slightly_over), "0x1.0p+1");
+  EXPECT_EQ(format("%.2a", slightly_over), "0x1.00p+1");
+  EXPECT_EQ(format("%.3a", slightly_over), "0x1.000p+1");
+  EXPECT_EQ(format("%.4a", slightly_over), "0x1.0002p+1");
+  EXPECT_EQ(format("%.5a", slightly_over), "0x1.00018p+1");
+  EXPECT_EQ(format("%.6a", slightly_over), "0x1.000180p+1");
+
+  // 0x1.00017fffp+0
+  const double slightly_under = 1.000022887950763106346130371093750;
+  EXPECT_EQ(format("%.0a", slightly_under), "0x1p+0");
+  EXPECT_EQ(format("%.1a", slightly_under), "0x1.0p+0");
+  EXPECT_EQ(format("%.2a", slightly_under), "0x1.00p+0");
+  EXPECT_EQ(format("%.3a", slightly_under), "0x1.000p+0");
+  EXPECT_EQ(format("%.4a", slightly_under), "0x1.0001p+0");
+  EXPECT_EQ(format("%.5a", slightly_under), "0x1.00018p+0");
+  EXPECT_EQ(format("%.6a", slightly_under), "0x1.000180p+0");
+  EXPECT_EQ(format("%.7a", slightly_under), "0x1.0001800p+0");
+
+  // 0x1.1b3829ac28058p+3
+  const double hex_value = 8.85060580848964661981881363317370414733886718750;
+  EXPECT_EQ(format("%.0a", hex_value), "0x1p+3");
+  EXPECT_EQ(format("%.1a", hex_value), "0x1.2p+3");
+  EXPECT_EQ(format("%.2a", hex_value), "0x1.1bp+3");
+  EXPECT_EQ(format("%.3a", hex_value), "0x1.1b4p+3");
+  EXPECT_EQ(format("%.4a", hex_value), "0x1.1b38p+3");
+  EXPECT_EQ(format("%.5a", hex_value), "0x1.1b383p+3");
+  EXPECT_EQ(format("%.6a", hex_value), "0x1.1b382ap+3");
+  EXPECT_EQ(format("%.7a", hex_value), "0x1.1b3829bp+3");
+  EXPECT_EQ(format("%.8a", hex_value), "0x1.1b3829acp+3");
+  EXPECT_EQ(format("%.9a", hex_value), "0x1.1b3829ac3p+3");
+  EXPECT_EQ(format("%.10a", hex_value), "0x1.1b3829ac28p+3");
+  EXPECT_EQ(format("%.11a", hex_value), "0x1.1b3829ac280p+3");
+  EXPECT_EQ(format("%.12a", hex_value), "0x1.1b3829ac2806p+3");
+  EXPECT_EQ(format("%.13a", hex_value), "0x1.1b3829ac28058p+3");
+  EXPECT_EQ(format("%.14a", hex_value), "0x1.1b3829ac280580p+3");
+  EXPECT_EQ(format("%.15a", hex_value), "0x1.1b3829ac2805800p+3");
+  EXPECT_EQ(format("%.16a", hex_value), "0x1.1b3829ac28058000p+3");
+  EXPECT_EQ(format("%.17a", hex_value), "0x1.1b3829ac280580000p+3");
+  EXPECT_EQ(format("%.18a", hex_value), "0x1.1b3829ac2805800000p+3");
+  EXPECT_EQ(format("%.19a", hex_value), "0x1.1b3829ac28058000000p+3");
+  EXPECT_EQ(format("%.20a", hex_value), "0x1.1b3829ac280580000000p+3");
+  EXPECT_EQ(format("%.21a", hex_value), "0x1.1b3829ac2805800000000p+3");
+
+  // 0x1.0818283848586p+3
+  const double hex_value2 = 8.2529488658208371987257123691961169242858886718750;
+  EXPECT_EQ(format("%.0a", hex_value2), "0x1p+3");
+  EXPECT_EQ(format("%.1a", hex_value2), "0x1.1p+3");
+  EXPECT_EQ(format("%.2a", hex_value2), "0x1.08p+3");
+  EXPECT_EQ(format("%.3a", hex_value2), "0x1.082p+3");
+  EXPECT_EQ(format("%.4a", hex_value2), "0x1.0818p+3");
+  EXPECT_EQ(format("%.5a", hex_value2), "0x1.08183p+3");
+  EXPECT_EQ(format("%.6a", hex_value2), "0x1.081828p+3");
+  EXPECT_EQ(format("%.7a", hex_value2), "0x1.0818284p+3");
+  EXPECT_EQ(format("%.8a", hex_value2), "0x1.08182838p+3");
+  EXPECT_EQ(format("%.9a", hex_value2), "0x1.081828385p+3");
+  EXPECT_EQ(format("%.10a", hex_value2), "0x1.0818283848p+3");
+  EXPECT_EQ(format("%.11a", hex_value2), "0x1.08182838486p+3");
+  EXPECT_EQ(format("%.12a", hex_value2), "0x1.081828384858p+3");
+  EXPECT_EQ(format("%.13a", hex_value2), "0x1.0818283848586p+3");
+  EXPECT_EQ(format("%.14a", hex_value2), "0x1.08182838485860p+3");
+  EXPECT_EQ(format("%.15a", hex_value2), "0x1.081828384858600p+3");
+  EXPECT_EQ(format("%.16a", hex_value2), "0x1.0818283848586000p+3");
+  EXPECT_EQ(format("%.17a", hex_value2), "0x1.08182838485860000p+3");
+  EXPECT_EQ(format("%.18a", hex_value2), "0x1.081828384858600000p+3");
+  EXPECT_EQ(format("%.19a", hex_value2), "0x1.0818283848586000000p+3");
+  EXPECT_EQ(format("%.20a", hex_value2), "0x1.08182838485860000000p+3");
+  EXPECT_EQ(format("%.21a", hex_value2), "0x1.081828384858600000000p+3");
+}
+
+TEST_F(FormatConvertTest, LongDoubleRoundA) {
+  if (std::numeric_limits<long double>::digits % 4 != 0) {
+    // This test doesn't really make sense to run on platforms where a long
+    // double has a different mantissa size (mod 4) than Prod, since then the
+    // leading digit will be formatted differently.
+    return;
+  }
+  const NativePrintfTraits &native_traits = VerifyNativeImplementation();
+  std::string s;
+  const auto format = [&](const char *fmt, long double d) -> std::string & {
+    s.clear();
+    FormatArgImpl args[1] = {FormatArgImpl(d)};
+    AppendPack(&s, UntypedFormatSpecImpl(fmt), absl::MakeSpan(args));
+    if (native_traits.hex_float_has_glibc_rounding &&
+        native_traits.hex_float_optimizes_leading_digit_bit_count) {
+      EXPECT_EQ(StrPrint(fmt, d), s);
+    }
+    return s;
+  };
+
+  // 0x8.8p+4
+  const long double on_boundary_even = 136.0;
+  EXPECT_EQ(format("%.0La", on_boundary_even), "0x8p+4");
+  EXPECT_EQ(format("%.1La", on_boundary_even), "0x8.8p+4");
+  EXPECT_EQ(format("%.2La", on_boundary_even), "0x8.80p+4");
+  EXPECT_EQ(format("%.3La", on_boundary_even), "0x8.800p+4");
+  EXPECT_EQ(format("%.4La", on_boundary_even), "0x8.8000p+4");
+  EXPECT_EQ(format("%.5La", on_boundary_even), "0x8.80000p+4");
+  EXPECT_EQ(format("%.6La", on_boundary_even), "0x8.800000p+4");
+
+  // 0x9.8p+4
+  const long double on_boundary_odd = 152.0;
+  EXPECT_EQ(format("%.0La", on_boundary_odd), "0xap+4");
+  EXPECT_EQ(format("%.1La", on_boundary_odd), "0x9.8p+4");
+  EXPECT_EQ(format("%.2La", on_boundary_odd), "0x9.80p+4");
+  EXPECT_EQ(format("%.3La", on_boundary_odd), "0x9.800p+4");
+  EXPECT_EQ(format("%.4La", on_boundary_odd), "0x9.8000p+4");
+  EXPECT_EQ(format("%.5La", on_boundary_odd), "0x9.80000p+4");
+  EXPECT_EQ(format("%.6La", on_boundary_odd), "0x9.800000p+4");
+
+  // 0x8.80001p+24
+  const long double slightly_over = 142606352.0;
+  EXPECT_EQ(format("%.0La", slightly_over), "0x9p+24");
+  EXPECT_EQ(format("%.1La", slightly_over), "0x8.8p+24");
+  EXPECT_EQ(format("%.2La", slightly_over), "0x8.80p+24");
+  EXPECT_EQ(format("%.3La", slightly_over), "0x8.800p+24");
+  EXPECT_EQ(format("%.4La", slightly_over), "0x8.8000p+24");
+  EXPECT_EQ(format("%.5La", slightly_over), "0x8.80001p+24");
+  EXPECT_EQ(format("%.6La", slightly_over), "0x8.800010p+24");
+
+  // 0x8.7ffffp+24
+  const long double slightly_under = 142606320.0;
+  EXPECT_EQ(format("%.0La", slightly_under), "0x8p+24");
+  EXPECT_EQ(format("%.1La", slightly_under), "0x8.8p+24");
+  EXPECT_EQ(format("%.2La", slightly_under), "0x8.80p+24");
+  EXPECT_EQ(format("%.3La", slightly_under), "0x8.800p+24");
+  EXPECT_EQ(format("%.4La", slightly_under), "0x8.8000p+24");
+  EXPECT_EQ(format("%.5La", slightly_under), "0x8.7ffffp+24");
+  EXPECT_EQ(format("%.6La", slightly_under), "0x8.7ffff0p+24");
+  EXPECT_EQ(format("%.7La", slightly_under), "0x8.7ffff00p+24");
+
+  // 0xc.0828384858688000p+128
+  const long double eights = 4094231060438608800781871108094404067328.0;
+  EXPECT_EQ(format("%.0La", eights), "0xcp+128");
+  EXPECT_EQ(format("%.1La", eights), "0xc.1p+128");
+  EXPECT_EQ(format("%.2La", eights), "0xc.08p+128");
+  EXPECT_EQ(format("%.3La", eights), "0xc.083p+128");
+  EXPECT_EQ(format("%.4La", eights), "0xc.0828p+128");
+  EXPECT_EQ(format("%.5La", eights), "0xc.08284p+128");
+  EXPECT_EQ(format("%.6La", eights), "0xc.082838p+128");
+  EXPECT_EQ(format("%.7La", eights), "0xc.0828385p+128");
+  EXPECT_EQ(format("%.8La", eights), "0xc.08283848p+128");
+  EXPECT_EQ(format("%.9La", eights), "0xc.082838486p+128");
+  EXPECT_EQ(format("%.10La", eights), "0xc.0828384858p+128");
+  EXPECT_EQ(format("%.11La", eights), "0xc.08283848587p+128");
+  EXPECT_EQ(format("%.12La", eights), "0xc.082838485868p+128");
+  EXPECT_EQ(format("%.13La", eights), "0xc.0828384858688p+128");
+  EXPECT_EQ(format("%.14La", eights), "0xc.08283848586880p+128");
+  EXPECT_EQ(format("%.15La", eights), "0xc.082838485868800p+128");
+  EXPECT_EQ(format("%.16La", eights), "0xc.0828384858688000p+128");
+}
+
 // We don't actually store the results. This is just to exercise the rest of the
 // machinery.
 struct NullSink {
@@ -735,6 +1074,7 @@ TEST_F(FormatConvertTest, LongDouble) {
   // implementation against the native one there.
   return;
 #endif  // _MSC_VER
+  const NativePrintfTraits &native_traits = VerifyNativeImplementation();
   const char *const kFormats[] = {"%",    "%.3", "%8.5", "%9",  "%.5000",
                                   "%.60", "%+",  "% ",   "%-10"};
 
@@ -777,12 +1117,20 @@ TEST_F(FormatConvertTest, LongDouble) {
                    'e', 'E'}) {
       std::string fmt_str = std::string(fmt) + 'L' + f;
 
-      if (fmt == absl::string_view("%.5000") && f != 'f' && f != 'F') {
+      if (fmt == absl::string_view("%.5000") && f != 'f' && f != 'F' &&
+          f != 'a' && f != 'A') {
         // This particular test takes way too long with snprintf.
         // Disable for the case we are not implementing natively.
         continue;
       }
 
+      if (f == 'a' || f == 'A') {
+        if (!native_traits.hex_float_has_glibc_rounding ||
+            !native_traits.hex_float_optimizes_leading_digit_bit_count) {
+          continue;
+        }
+      }
+
       for (auto d : doubles) {
         FormatArgImpl arg(d);
         UntypedFormatSpecImpl format(fmt_str);
@@ -797,7 +1145,8 @@ TEST_F(FormatConvertTest, LongDouble) {
   }
 }
 
-TEST_F(FormatConvertTest, IntAsFloat) {
+TEST_F(FormatConvertTest, IntAsDouble) {
+  const NativePrintfTraits &native_traits = VerifyNativeImplementation();
   const int kMin = std::numeric_limits<int>::min();
   const int kMax = std::numeric_limits<int>::max();
   const int ia[] = {
@@ -813,14 +1162,17 @@ TEST_F(FormatConvertTest, IntAsFloat) {
       const char *fmt;
     };
     const double dx = static_cast<double>(fx);
-    const Expectation kExpect[] = {
-      { __LINE__, StrPrint("%f", dx), "%f" },
-      { __LINE__, StrPrint("%12f", dx), "%12f" },
-      { __LINE__, StrPrint("%.12f", dx), "%.12f" },
-      { __LINE__, StrPrint("%12a", dx), "%12a" },
-      { __LINE__, StrPrint("%.12a", dx), "%.12a" },
+    std::vector<Expectation> expect = {
+        {__LINE__, StrPrint("%f", dx), "%f"},
+        {__LINE__, StrPrint("%12f", dx), "%12f"},
+        {__LINE__, StrPrint("%.12f", dx), "%.12f"},
+        {__LINE__, StrPrint("%.12a", dx), "%.12a"},
     };
-    for (const Expectation &e : kExpect) {
+    if (native_traits.hex_float_uses_minimal_precision_when_not_specified) {
+      Expectation ex = {__LINE__, StrPrint("%12a", dx), "%12a"};
+      expect.push_back(ex);
+    }
+    for (const Expectation &e : expect) {
       SCOPED_TRACE(e.line);
       SCOPED_TRACE(e.fmt);
       UntypedFormatSpecImpl format(e.fmt);
@@ -865,6 +1217,25 @@ TEST_F(FormatConvertTest, ExpectedFailures) {
   EXPECT_TRUE(FormatFails("%*d", ""));
 }
 
+// Sanity check to make sure that we are testing what we think we're testing on
+// e.g. the x86_64+glibc platform.
+TEST_F(FormatConvertTest, GlibcHasCorrectTraits) {
+#if !defined(__GLIBC__) || !defined(__x86_64__)
+  return;
+#endif
+  const NativePrintfTraits &native_traits = VerifyNativeImplementation();
+  // If one of the following tests break then it is either because the above PP
+  // macro guards failed to exclude a new platform (likely) or because something
+  // has changed in the implemention of glibc sprintf float formatting behavior.
+  // If the latter, then the code that computes these flags needs to be
+  // revisited and/or possibly the StrFormat implementation.
+  EXPECT_TRUE(native_traits.hex_float_has_glibc_rounding);
+  EXPECT_TRUE(native_traits.hex_float_prefers_denormal_repr);
+  EXPECT_TRUE(
+      native_traits.hex_float_uses_minimal_precision_when_not_specified);
+  EXPECT_TRUE(native_traits.hex_float_optimizes_leading_digit_bit_count);
+}
+
 }  // namespace
 }  // namespace str_format_internal
 ABSL_NAMESPACE_END
diff --git a/third_party/abseil_cpp/absl/strings/internal/str_format/extension.cc b/third_party/abseil_cpp/absl/strings/internal/str_format/extension.cc
index 94f2b9c209aa..bb0d96cf3216 100644
--- a/third_party/abseil_cpp/absl/strings/internal/str_format/extension.cc
+++ b/third_party/abseil_cpp/absl/strings/internal/str_format/extension.cc
@@ -33,6 +33,29 @@ std::string Flags::ToString() const {
   return s;
 }
 
+#define ABSL_INTERNAL_X_VAL(id) \
+  constexpr absl::FormatConversionChar FormatConversionCharInternal::id;
+ABSL_INTERNAL_CONVERSION_CHARS_EXPAND_(ABSL_INTERNAL_X_VAL, )
+#undef ABSL_INTERNAL_X_VAL
+// NOLINTNEXTLINE(readability-redundant-declaration)
+constexpr absl::FormatConversionChar FormatConversionCharInternal::kNone;
+
+#define ABSL_INTERNAL_CHAR_SET_CASE(c) \
+  constexpr FormatConversionCharSet FormatConversionCharSetInternal::c;
+ABSL_INTERNAL_CONVERSION_CHARS_EXPAND_(ABSL_INTERNAL_CHAR_SET_CASE, )
+#undef ABSL_INTERNAL_CHAR_SET_CASE
+
+// NOLINTNEXTLINE(readability-redundant-declaration)
+constexpr FormatConversionCharSet FormatConversionCharSetInternal::kStar;
+// NOLINTNEXTLINE(readability-redundant-declaration)
+constexpr FormatConversionCharSet FormatConversionCharSetInternal::kIntegral;
+// NOLINTNEXTLINE(readability-redundant-declaration)
+constexpr FormatConversionCharSet FormatConversionCharSetInternal::kFloating;
+// NOLINTNEXTLINE(readability-redundant-declaration)
+constexpr FormatConversionCharSet FormatConversionCharSetInternal::kNumeric;
+// NOLINTNEXTLINE(readability-redundant-declaration)
+constexpr FormatConversionCharSet FormatConversionCharSetInternal::kPointer;
+
 bool FormatSinkImpl::PutPaddedString(string_view value, int width,
                                      int precision, bool left) {
   size_t space_remaining = 0;
diff --git a/third_party/abseil_cpp/absl/strings/internal/str_format/extension.h b/third_party/abseil_cpp/absl/strings/internal/str_format/extension.h
index 6c60c6c3a379..a9b9e137deb2 100644
--- a/third_party/abseil_cpp/absl/strings/internal/str_format/extension.h
+++ b/third_party/abseil_cpp/absl/strings/internal/str_format/extension.h
@@ -31,11 +31,11 @@
 namespace absl {
 ABSL_NAMESPACE_BEGIN
 
-namespace str_format_internal {
-
 enum class FormatConversionChar : uint8_t;
 enum class FormatConversionCharSet : uint64_t;
 
+namespace str_format_internal {
+
 class FormatRawSinkImpl {
  public:
   // Implicitly convert from any type that provides the hook function as
@@ -361,14 +361,12 @@ struct FormatConversionCharSetInternal {
   static constexpr FormatConversionCharSet kStar =
       FormatConversionCharToConvValue('*');
 
-  // Some predefined values (TODO(matthewbr), delete any that are unused).
   static constexpr FormatConversionCharSet kIntegral =
       FormatConversionCharSetUnion(d, i, u, o, x, X);
   static constexpr FormatConversionCharSet kFloating =
       FormatConversionCharSetUnion(a, e, f, g, A, E, F, G);
   static constexpr FormatConversionCharSet kNumeric =
       FormatConversionCharSetUnion(kIntegral, kFloating);
-  static constexpr FormatConversionCharSet kString = s;
   static constexpr FormatConversionCharSet kPointer = p;
 };
 
diff --git a/third_party/abseil_cpp/absl/strings/internal/str_format/extension_test.cc b/third_party/abseil_cpp/absl/strings/internal/str_format/extension_test.cc
index 0a023f9c0333..1c93fdb1c75b 100644
--- a/third_party/abseil_cpp/absl/strings/internal/str_format/extension_test.cc
+++ b/third_party/abseil_cpp/absl/strings/internal/str_format/extension_test.cc
@@ -80,4 +80,19 @@ TEST(FormatExtensionTest, SinkAppendChars) {
     EXPECT_EQ(actual, expected);
   }
 }
+
+TEST(FormatExtensionTest, VerifyEnumEquality) {
+#define X_VAL(id)                           \
+  EXPECT_EQ(absl::FormatConversionChar::id, \
+            absl::str_format_internal::FormatConversionCharInternal::id);
+  ABSL_INTERNAL_CONVERSION_CHARS_EXPAND_(X_VAL, );
+#undef X_VAL
+
+#define X_VAL(id)                              \
+  EXPECT_EQ(absl::FormatConversionCharSet::id, \
+            absl::str_format_internal::FormatConversionCharSetInternal::id);
+  ABSL_INTERNAL_CONVERSION_CHARS_EXPAND_(X_VAL, );
+#undef X_VAL
+}
+
 }  // namespace
diff --git a/third_party/abseil_cpp/absl/strings/internal/str_format/float_conversion.cc b/third_party/abseil_cpp/absl/strings/internal/str_format/float_conversion.cc
index 10e4695411b2..0ded0a66afa9 100644
--- a/third_party/abseil_cpp/absl/strings/internal/str_format/float_conversion.cc
+++ b/third_party/abseil_cpp/absl/strings/internal/str_format/float_conversion.cc
@@ -1,3 +1,17 @@
+// Copyright 2020 The Abseil Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
 #include "absl/strings/internal/str_format/float_conversion.h"
 
 #include <string.h>
@@ -15,6 +29,7 @@
 #include "absl/functional/function_ref.h"
 #include "absl/meta/type_traits.h"
 #include "absl/numeric/int128.h"
+#include "absl/strings/numbers.h"
 #include "absl/types/optional.h"
 #include "absl/types/span.h"
 
@@ -119,7 +134,7 @@ class BinaryToDecimal {
     assert(exp > 0);
     assert(exp <= std::numeric_limits<long double>::max_exponent);
     static_assert(
-        StackArray::kMaxCapacity >=
+        static_cast<int>(StackArray::kMaxCapacity) >=
             ChunksNeeded(std::numeric_limits<long double>::max_exponent),
         "");
 
@@ -204,7 +219,7 @@ class BinaryToDecimal {
   }
 
  private:
-  static constexpr size_t kDigitsPerChunk = 9;
+  static constexpr int kDigitsPerChunk = 9;
 
   int decimal_start_;
   int decimal_end_;
@@ -441,8 +456,10 @@ struct Padding {
 };
 
 Padding ExtraWidthToPadding(size_t total_size, const FormatState &state) {
-  if (state.conv.width() < 0 || state.conv.width() <= total_size)
+  if (state.conv.width() < 0 ||
+      static_cast<size_t>(state.conv.width()) <= total_size) {
     return {0, 0, 0};
+  }
   int missing_chars = state.conv.width() - total_size;
   if (state.conv.has_left_flag()) {
     return {0, 0, missing_chars};
@@ -453,26 +470,31 @@ Padding ExtraWidthToPadding(size_t total_size, const FormatState &state) {
   }
 }
 
-void FinalPrint(absl::string_view data, int trailing_zeros,
-                const FormatState &state) {
+void FinalPrint(const FormatState &state, absl::string_view data,
+                int padding_offset, int trailing_zeros,
+                absl::string_view data_postfix) {
   if (state.conv.width() < 0) {
     // No width specified. Fast-path.
     if (state.sign_char != '\0') state.sink->Append(1, state.sign_char);
     state.sink->Append(data);
     state.sink->Append(trailing_zeros, '0');
+    state.sink->Append(data_postfix);
     return;
   }
 
-  auto padding =
-      ExtraWidthToPadding((state.sign_char != '\0' ? 1 : 0) + data.size() +
-                              static_cast<size_t>(trailing_zeros),
-                          state);
+  auto padding = ExtraWidthToPadding((state.sign_char != '\0' ? 1 : 0) +
+                                         data.size() + data_postfix.size() +
+                                         static_cast<size_t>(trailing_zeros),
+                                     state);
 
   state.sink->Append(padding.left_spaces, ' ');
   if (state.sign_char != '\0') state.sink->Append(1, state.sign_char);
+  // Padding in general needs to be inserted somewhere in the middle of `data`.
+  state.sink->Append(data.substr(0, padding_offset));
   state.sink->Append(padding.zeros, '0');
-  state.sink->Append(data);
+  state.sink->Append(data.substr(padding_offset));
   state.sink->Append(trailing_zeros, '0');
+  state.sink->Append(data_postfix);
   state.sink->Append(padding.right_spaces, ' ');
 }
 
@@ -525,10 +547,11 @@ void FormatFFast(Int v, int exp, const FormatState &state) {
   // In `alt` mode (flag #) we keep the `.` even if there are no fractional
   // digits. In non-alt mode, we strip it.
   if (!state.ShouldPrintDot()) --size;
-  FinalPrint(absl::string_view(integral_digits_start, size),
+  FinalPrint(state, absl::string_view(integral_digits_start, size),
+             /*padding_offset=*/0,
              static_cast<int>(state.precision - (fractional_digits_end -
                                                  fractional_digits_start)),
-             state);
+             /*data_postfix=*/"");
 }
 
 // Slow %f formatter for when the shifted value does not fit in a uint128, and
@@ -655,6 +678,255 @@ void FormatF(Int mantissa, int exp, const FormatState &state) {
   return FormatFFast(mantissa, exp, state);
 }
 
+// Grab the group of four bits (nibble) from `n`. E.g., nibble 1 corresponds to
+// bits 4-7.
+template <typename Int>
+uint8_t GetNibble(Int n, int nibble_index) {
+  constexpr Int mask_low_nibble = Int{0xf};
+  int shift = nibble_index * 4;
+  n &= mask_low_nibble << shift;
+  return static_cast<uint8_t>((n >> shift) & 0xf);
+}
+
+// Add one to the given nibble, applying carry to higher nibbles. Returns true
+// if overflow, false otherwise.
+template <typename Int>
+bool IncrementNibble(int nibble_index, Int *n) {
+  constexpr int kShift = sizeof(Int) * 8 - 1;
+  constexpr int kNumNibbles = sizeof(Int) * 8 / 4;
+  Int before = *n >> kShift;
+  // Here we essentially want to take the number 1 and move it into the requsted
+  // nibble, then add it to *n to effectively increment the nibble. However,
+  // ASan will complain if we try to shift the 1 beyond the limits of the Int,
+  // i.e., if the nibble_index is out of range. So therefore we check for this
+  // and if we are out of range we just add 0 which leaves *n unchanged, which
+  // seems like the reasonable thing to do in that case.
+  *n += ((nibble_index >= kNumNibbles) ? 0 : (Int{1} << (nibble_index * 4)));
+  Int after = *n >> kShift;
+  return (before && !after) || (nibble_index >= kNumNibbles);
+}
+
+// Return a mask with 1's in the given nibble and all lower nibbles.
+template <typename Int>
+Int MaskUpToNibbleInclusive(int nibble_index) {
+  constexpr int kNumNibbles = sizeof(Int) * 8 / 4;
+  static const Int ones = ~Int{0};
+  return ones >> std::max(0, 4 * (kNumNibbles - nibble_index - 1));
+}
+
+// Return a mask with 1's below the given nibble.
+template <typename Int>
+Int MaskUpToNibbleExclusive(int nibble_index) {
+  return nibble_index <= 0 ? 0 : MaskUpToNibbleInclusive<Int>(nibble_index - 1);
+}
+
+template <typename Int>
+Int MoveToNibble(uint8_t nibble, int nibble_index) {
+  return Int{nibble} << (4 * nibble_index);
+}
+
+// Given mantissa size, find optimal # of mantissa bits to put in initial digit.
+//
+// In the hex representation we keep a single hex digit to the left of the dot.
+// However, the question as to how many bits of the mantissa should be put into
+// that hex digit in theory is arbitrary, but in practice it is optimal to
+// choose based on the size of the mantissa. E.g., for a `double`, there are 53
+// mantissa bits, so that means that we should put 1 bit to the left of the dot,
+// thereby leaving 52 bits to the right, which is evenly divisible by four and
+// thus all fractional digits represent actual precision. For a `long double`,
+// on the other hand, there are 64 bits of mantissa, thus we can use all four
+// bits for the initial hex digit and still have a number left over (60) that is
+// a multiple of four. Once again, the goal is to have all fractional digits
+// represent real precision.
+template <typename Float>
+constexpr int HexFloatLeadingDigitSizeInBits() {
+  return std::numeric_limits<Float>::digits % 4 > 0
+             ? std::numeric_limits<Float>::digits % 4
+             : 4;
+}
+
+// This function captures the rounding behavior of glibc for hex float
+// representations. E.g. when rounding 0x1.ab800000 to a precision of .2
+// ("%.2a") glibc will round up because it rounds toward the even number (since
+// 0xb is an odd number, it will round up to 0xc). However, when rounding at a
+// point that is not followed by 800000..., it disregards the parity and rounds
+// up if > 8 and rounds down if < 8.
+template <typename Int>
+bool HexFloatNeedsRoundUp(Int mantissa, int final_nibble_displayed,
+                          uint8_t leading) {
+  // If the last nibble (hex digit) to be displayed is the lowest on in the
+  // mantissa then that means that we don't have any further nibbles to inform
+  // rounding, so don't round.
+  if (final_nibble_displayed <= 0) {
+    return false;
+  }
+  int rounding_nibble_idx = final_nibble_displayed - 1;
+  constexpr int kTotalNibbles = sizeof(Int) * 8 / 4;
+  assert(final_nibble_displayed <= kTotalNibbles);
+  Int mantissa_up_to_rounding_nibble_inclusive =
+      mantissa & MaskUpToNibbleInclusive<Int>(rounding_nibble_idx);
+  Int eight = MoveToNibble<Int>(8, rounding_nibble_idx);
+  if (mantissa_up_to_rounding_nibble_inclusive != eight) {
+    return mantissa_up_to_rounding_nibble_inclusive > eight;
+  }
+  // Nibble in question == 8.
+  uint8_t round_if_odd = (final_nibble_displayed == kTotalNibbles)
+                             ? leading
+                             : GetNibble(mantissa, final_nibble_displayed);
+  return round_if_odd % 2 == 1;
+}
+
+// Stores values associated with a Float type needed by the FormatA
+// implementation in order to avoid templatizing that function by the Float
+// type.
+struct HexFloatTypeParams {
+  template <typename Float>
+  explicit HexFloatTypeParams(Float)
+      : min_exponent(std::numeric_limits<Float>::min_exponent - 1),
+        leading_digit_size_bits(HexFloatLeadingDigitSizeInBits<Float>()) {
+    assert(leading_digit_size_bits >= 1 && leading_digit_size_bits <= 4);
+  }
+
+  int min_exponent;
+  int leading_digit_size_bits;
+};
+
+// Hex Float Rounding. First check if we need to round; if so, then we do that
+// by manipulating (incrementing) the mantissa, that way we can later print the
+// mantissa digits by iterating through them in the same way regardless of
+// whether a rounding happened.
+template <typename Int>
+void FormatARound(bool precision_specified, const FormatState &state,
+                  uint8_t *leading, Int *mantissa, int *exp) {
+  constexpr int kTotalNibbles = sizeof(Int) * 8 / 4;
+  // Index of the last nibble that we could display given precision.
+  int final_nibble_displayed =
+      precision_specified ? std::max(0, (kTotalNibbles - state.precision)) : 0;
+  if (HexFloatNeedsRoundUp(*mantissa, final_nibble_displayed, *leading)) {
+    // Need to round up.
+    bool overflow = IncrementNibble(final_nibble_displayed, mantissa);
+    *leading += (overflow ? 1 : 0);
+    if (ABSL_PREDICT_FALSE(*leading > 15)) {
+      // We have overflowed the leading digit. This would mean that we would
+      // need two hex digits to the left of the dot, which is not allowed. So
+      // adjust the mantissa and exponent so that the result is always 1.0eXXX.
+      *leading = 1;
+      *mantissa = 0;
+      *exp += 4;
+    }
+  }
+  // Now that we have handled a possible round-up we can go ahead and zero out
+  // all the nibbles of the mantissa that we won't need.
+  if (precision_specified) {
+    *mantissa &= ~MaskUpToNibbleExclusive<Int>(final_nibble_displayed);
+  }
+}
+
+template <typename Int>
+void FormatANormalize(const HexFloatTypeParams float_traits, uint8_t *leading,
+                      Int *mantissa, int *exp) {
+  constexpr int kIntBits = sizeof(Int) * 8;
+  static const Int kHighIntBit = Int{1} << (kIntBits - 1);
+  const int kLeadDigitBitsCount = float_traits.leading_digit_size_bits;
+  // Normalize mantissa so that highest bit set is in MSB position, unless we
+  // get interrupted by the exponent threshold.
+  while (*mantissa && !(*mantissa & kHighIntBit)) {
+    if (ABSL_PREDICT_FALSE(*exp - 1 < float_traits.min_exponent)) {
+      *mantissa >>= (float_traits.min_exponent - *exp);
+      *exp = float_traits.min_exponent;
+      return;
+    }
+    *mantissa <<= 1;
+    --*exp;
+  }
+  // Extract bits for leading digit then shift them away leaving the
+  // fractional part.
+  *leading =
+      static_cast<uint8_t>(*mantissa >> (kIntBits - kLeadDigitBitsCount));
+  *exp -= (*mantissa != 0) ? kLeadDigitBitsCount : *exp;
+  *mantissa <<= kLeadDigitBitsCount;
+}
+
+template <typename Int>
+void FormatA(const HexFloatTypeParams float_traits, Int mantissa, int exp,
+             bool uppercase, const FormatState &state) {
+  // Int properties.
+  constexpr int kIntBits = sizeof(Int) * 8;
+  constexpr int kTotalNibbles = sizeof(Int) * 8 / 4;
+  // Did the user specify a precision explicitly?
+  const bool precision_specified = state.conv.precision() >= 0;
+
+  // ========== Normalize/Denormalize ==========
+  exp += kIntBits;  // make all digits fractional digits.
+  // This holds the (up to four) bits of leading digit, i.e., the '1' in the
+  // number 0x1.e6fp+2. It's always > 0 unless number is zero or denormal.
+  uint8_t leading = 0;
+  FormatANormalize(float_traits, &leading, &mantissa, &exp);
+
+  // =============== Rounding ==================
+  // Check if we need to round; if so, then we do that by manipulating
+  // (incrementing) the mantissa before beginning to print characters.
+  FormatARound(precision_specified, state, &leading, &mantissa, &exp);
+
+  // ============= Format Result ===============
+  // This buffer holds the "0x1.ab1de3" portion of "0x1.ab1de3pe+2". Compute the
+  // size with long double which is the largest of the floats.
+  constexpr size_t kBufSizeForHexFloatRepr =
+      2                                               // 0x
+      + std::numeric_limits<long double>::digits / 4  // number of hex digits
+      + 1                                             // round up
+      + 1;                                            // "." (dot)
+  char digits_buffer[kBufSizeForHexFloatRepr];
+  char *digits_iter = digits_buffer;
+  const char *const digits =
+      static_cast<const char *>("0123456789ABCDEF0123456789abcdef") +
+      (uppercase ? 0 : 16);
+
+  // =============== Hex Prefix ================
+  *digits_iter++ = '0';
+  *digits_iter++ = uppercase ? 'X' : 'x';
+
+  // ========== Non-Fractional Digit ===========
+  *digits_iter++ = digits[leading];
+
+  // ================== Dot ====================
+  // There are three reasons we might need a dot. Keep in mind that, at this
+  // point, the mantissa holds only the fractional part.
+  if ((precision_specified && state.precision > 0) ||
+      (!precision_specified && mantissa > 0) || state.conv.has_alt_flag()) {
+    *digits_iter++ = '.';
+  }
+
+  // ============ Fractional Digits ============
+  int digits_emitted = 0;
+  while (mantissa > 0) {
+    *digits_iter++ = digits[GetNibble(mantissa, kTotalNibbles - 1)];
+    mantissa <<= 4;
+    ++digits_emitted;
+  }
+  int trailing_zeros =
+      precision_specified ? state.precision - digits_emitted : 0;
+  assert(trailing_zeros >= 0);
+  auto digits_result = string_view(digits_buffer, digits_iter - digits_buffer);
+
+  // =============== Exponent ==================
+  constexpr size_t kBufSizeForExpDecRepr =
+      numbers_internal::kFastToBufferSize  // requred for FastIntToBuffer
+      + 1                                  // 'p' or 'P'
+      + 1;                                 // '+' or '-'
+  char exp_buffer[kBufSizeForExpDecRepr];
+  exp_buffer[0] = uppercase ? 'P' : 'p';
+  exp_buffer[1] = exp >= 0 ? '+' : '-';
+  numbers_internal::FastIntToBuffer(exp < 0 ? -exp : exp, exp_buffer + 2);
+
+  // ============ Assemble Result ==============
+  FinalPrint(state,           //
+             digits_result,   // 0xN.NNN...
+             2,               // offset in `data` to start padding if needed.
+             trailing_zeros,  // num remaining mantissa padding zeros
+             exp_buffer);     // exponent
+}
+
 char *CopyStringTo(absl::string_view v, char *out) {
   std::memcpy(out, v.data(), v.size());
   return out + v.size();
@@ -1103,7 +1375,10 @@ bool FloatToSink(const Float v, const FormatConversionSpecImpl &conv,
     }
   } else if (c == FormatConversionCharInternal::a ||
              c == FormatConversionCharInternal::A) {
-    return FallbackToSnprintf(v, conv, sink);
+    bool uppercase = (c == FormatConversionCharInternal::A);
+    FormatA(HexFloatTypeParams(Float{}), decomposed.mantissa,
+            decomposed.exponent, uppercase, {sign_char, precision, conv, sink});
+    return true;
   } else {
     return false;
   }
@@ -1131,7 +1406,7 @@ bool ConvertFloatImpl(long double v, const FormatConversionSpecImpl &conv,
 
 bool ConvertFloatImpl(float v, const FormatConversionSpecImpl &conv,
                       FormatSinkImpl *sink) {
-  return FloatToSink(v, conv, sink);
+  return FloatToSink(static_cast<double>(v), conv, sink);
 }
 
 bool ConvertFloatImpl(double v, const FormatConversionSpecImpl &conv,
diff --git a/third_party/abseil_cpp/absl/strings/internal/str_format/float_conversion.h b/third_party/abseil_cpp/absl/strings/internal/str_format/float_conversion.h
index e78bc19106ff..71100e714257 100644
--- a/third_party/abseil_cpp/absl/strings/internal/str_format/float_conversion.h
+++ b/third_party/abseil_cpp/absl/strings/internal/str_format/float_conversion.h
@@ -1,3 +1,17 @@
+// Copyright 2020 The Abseil Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
 #ifndef ABSL_STRINGS_INTERNAL_STR_FORMAT_FLOAT_CONVERSION_H_
 #define ABSL_STRINGS_INTERNAL_STR_FORMAT_FLOAT_CONVERSION_H_
 
diff --git a/third_party/abseil_cpp/absl/strings/internal/str_format/parser.cc b/third_party/abseil_cpp/absl/strings/internal/str_format/parser.cc
index cc55dfa9c74e..f308d0235120 100644
--- a/third_party/abseil_cpp/absl/strings/internal/str_format/parser.cc
+++ b/third_party/abseil_cpp/absl/strings/internal/str_format/parser.cc
@@ -1,3 +1,17 @@
+// Copyright 2020 The Abseil Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
 #include "absl/strings/internal/str_format/parser.h"
 
 #include <assert.h>
diff --git a/third_party/abseil_cpp/absl/strings/internal/str_format/parser.h b/third_party/abseil_cpp/absl/strings/internal/str_format/parser.h
index fffed04fa072..6504dd3ddc20 100644
--- a/third_party/abseil_cpp/absl/strings/internal/str_format/parser.h
+++ b/third_party/abseil_cpp/absl/strings/internal/str_format/parser.h
@@ -1,3 +1,17 @@
+// Copyright 2020 The Abseil Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
 #ifndef ABSL_STRINGS_INTERNAL_STR_FORMAT_PARSER_H_
 #define ABSL_STRINGS_INTERNAL_STR_FORMAT_PARSER_H_
 
diff --git a/third_party/abseil_cpp/absl/strings/internal/str_format/parser_test.cc b/third_party/abseil_cpp/absl/strings/internal/str_format/parser_test.cc
index 5aced987200d..a5fa1c79aaf4 100644
--- a/third_party/abseil_cpp/absl/strings/internal/str_format/parser_test.cc
+++ b/third_party/abseil_cpp/absl/strings/internal/str_format/parser_test.cc
@@ -1,3 +1,17 @@
+// Copyright 2020 The Abseil Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
 #include "absl/strings/internal/str_format/parser.h"
 
 #include <string.h>
diff --git a/third_party/abseil_cpp/absl/strings/internal/str_split_internal.h b/third_party/abseil_cpp/absl/strings/internal/str_split_internal.h
index 6f5bc095fbbe..a2f41c153131 100644
--- a/third_party/abseil_cpp/absl/strings/internal/str_split_internal.h
+++ b/third_party/abseil_cpp/absl/strings/internal/str_split_internal.h
@@ -51,9 +51,9 @@ ABSL_NAMESPACE_BEGIN
 namespace strings_internal {
 
 // This class is implicitly constructible from everything that absl::string_view
-// is implicitly constructible from. If it's constructed from a temporary
-// string, the data is moved into a data member so its lifetime matches that of
-// the ConvertibleToStringView instance.
+// is implicitly constructible from, except for rvalue strings.  This means it
+// can be used as a function parameter in places where passing a temporary
+// string might cause memory lifetime issues.
 class ConvertibleToStringView {
  public:
   ConvertibleToStringView(const char* s)  // NOLINT(runtime/explicit)
@@ -65,41 +65,12 @@ class ConvertibleToStringView {
       : value_(s) {}
 
   // Matches rvalue strings and moves their data to a member.
-  ConvertibleToStringView(std::string&& s)  // NOLINT(runtime/explicit)
-      : copy_(std::move(s)), value_(copy_) {}
-
-  ConvertibleToStringView(const ConvertibleToStringView& other)
-      : copy_(other.copy_),
-        value_(other.IsSelfReferential() ? copy_ : other.value_) {}
-
-  ConvertibleToStringView(ConvertibleToStringView&& other) {
-    StealMembers(std::move(other));
-  }
-
-  ConvertibleToStringView& operator=(ConvertibleToStringView other) {
-    StealMembers(std::move(other));
-    return *this;
-  }
+  ConvertibleToStringView(std::string&& s) = delete;
+  ConvertibleToStringView(const std::string&& s) = delete;
 
   absl::string_view value() const { return value_; }
 
  private:
-  // 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_;
-    }
-  }
-
-  // Holds the data moved from temporary std::string arguments. Declared first
-  // so that 'value' can refer to 'copy_'.
-  std::string copy_;
   absl::string_view value_;
 };
 
@@ -273,7 +244,11 @@ struct SplitterIsConvertibleTo
 // the split strings: only strings for which the predicate returns true will be
 // kept. A Predicate object is any unary functor that takes an absl::string_view
 // and returns bool.
-template <typename Delimiter, typename Predicate>
+//
+// The StringType parameter can be either string_view or string, depending on
+// whether the Splitter refers to a string stored elsewhere, or if the string
+// resides inside the Splitter itself.
+template <typename Delimiter, typename Predicate, typename StringType>
 class Splitter {
  public:
   using DelimiterType = Delimiter;
@@ -281,12 +256,12 @@ class Splitter {
   using const_iterator = strings_internal::SplitIterator<Splitter>;
   using value_type = typename std::iterator_traits<const_iterator>::value_type;
 
-  Splitter(ConvertibleToStringView input_text, Delimiter d, Predicate p)
+  Splitter(StringType input_text, Delimiter d, Predicate p)
       : text_(std::move(input_text)),
         delimiter_(std::move(d)),
         predicate_(std::move(p)) {}
 
-  absl::string_view text() const { return text_.value(); }
+  absl::string_view text() const { return text_; }
   const Delimiter& delimiter() const { return delimiter_; }
   const Predicate& predicate() const { return predicate_; }
 
@@ -336,7 +311,7 @@ class Splitter {
     Container operator()(const Splitter& splitter) const {
       Container c;
       auto it = std::inserter(c, c.end());
-      for (const auto sp : splitter) {
+      for (const auto& sp : splitter) {
         *it++ = ValueType(sp);
       }
       return c;
@@ -401,7 +376,7 @@ class Splitter {
       Container m;
       typename Container::iterator it;
       bool insert = true;
-      for (const auto sp : splitter) {
+      for (const auto& sp : splitter) {
         if (insert) {
           it = Inserter<Container>::Insert(&m, First(sp), Second());
         } else {
@@ -443,7 +418,7 @@ class Splitter {
     };
   };
 
-  ConvertibleToStringView text_;
+  StringType text_;
   Delimiter delimiter_;
   Predicate predicate_;
 };
diff --git a/third_party/abseil_cpp/absl/strings/internal/string_constant.h b/third_party/abseil_cpp/absl/strings/internal/string_constant.h
new file mode 100644
index 000000000000..b15f1d9bcfac
--- /dev/null
+++ b/third_party/abseil_cpp/absl/strings/internal/string_constant.h
@@ -0,0 +1,70 @@
+// Copyright 2020 The Abseil Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#ifndef ABSL_STRINGS_INTERNAL_STRING_CONSTANT_H_
+#define ABSL_STRINGS_INTERNAL_STRING_CONSTANT_H_
+
+#include "absl/meta/type_traits.h"
+#include "absl/strings/string_view.h"
+
+namespace absl {
+ABSL_NAMESPACE_BEGIN
+namespace strings_internal {
+
+// StringConstant<T> represents a compile time string constant.
+// It can be accessed via its `absl::string_view value` static member.
+// It is guaranteed that the `string_view` returned has constant `.data()`,
+// constant `.size()` and constant `value[i]` for all `0 <= i < .size()`
+//
+// The `T` is an opaque type. It is guaranteed that different string constants
+// will have different values of `T`. This allows users to associate the string
+// constant with other static state at compile time.
+//
+// Instances should be made using the `MakeStringConstant()` factory function
+// below.
+template <typename T>
+struct StringConstant {
+ private:
+  // Returns true if `view` points to constant data.
+  // Otherwise, it can't be constant evaluated.
+  static constexpr bool ValidateConstant(absl::string_view view) {
+    return view.empty() || 2 * view[0] != 1;
+  }
+
+ public:
+  static constexpr absl::string_view value = T{}();
+  constexpr absl::string_view operator()() const { return value; }
+
+  static_assert(ValidateConstant(value),
+                "The input string_view must point to constant data.");
+};
+
+template <typename T>
+constexpr absl::string_view StringConstant<T>::value;  // NOLINT
+
+// Factory function for `StringConstant` instances.
+// It supports callables that have a constexpr default constructor and a
+// constexpr operator().
+// It must return an `absl::string_view` or `const char*` pointing to constant
+// data. This is validated at compile time.
+template <typename T>
+constexpr StringConstant<T> MakeStringConstant(T) {
+  return {};
+}
+
+}  // namespace strings_internal
+ABSL_NAMESPACE_END
+}  // namespace absl
+
+#endif  // ABSL_STRINGS_INTERNAL_STRING_CONSTANT_H_
diff --git a/third_party/abseil_cpp/absl/strings/internal/string_constant_test.cc b/third_party/abseil_cpp/absl/strings/internal/string_constant_test.cc
new file mode 100644
index 000000000000..392833cf1592
--- /dev/null
+++ b/third_party/abseil_cpp/absl/strings/internal/string_constant_test.cc
@@ -0,0 +1,60 @@
+// Copyright 2020 The Abseil Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#include "absl/strings/internal/string_constant.h"
+
+#include "absl/meta/type_traits.h"
+#include "gmock/gmock.h"
+#include "gtest/gtest.h"
+
+namespace {
+
+using absl::strings_internal::MakeStringConstant;
+
+struct Callable {
+  constexpr absl::string_view operator()() const {
+    return absl::string_view("Callable", 8);
+  }
+};
+
+TEST(StringConstant, Traits) {
+  constexpr auto str = MakeStringConstant(Callable{});
+  using T = decltype(str);
+
+  EXPECT_TRUE(std::is_empty<T>::value);
+  EXPECT_TRUE(std::is_trivial<T>::value);
+  EXPECT_TRUE(absl::is_trivially_default_constructible<T>::value);
+  EXPECT_TRUE(absl::is_trivially_copy_constructible<T>::value);
+  EXPECT_TRUE(absl::is_trivially_move_constructible<T>::value);
+  EXPECT_TRUE(absl::is_trivially_destructible<T>::value);
+}
+
+TEST(StringConstant, MakeFromCallable) {
+  constexpr auto str = MakeStringConstant(Callable{});
+  using T = decltype(str);
+  EXPECT_EQ(Callable{}(), T::value);
+  EXPECT_EQ(Callable{}(), str());
+}
+
+TEST(StringConstant, MakeFromStringConstant) {
+  // We want to make sure the StringConstant itself is a valid input to the
+  // factory function.
+  constexpr auto str = MakeStringConstant(Callable{});
+  constexpr auto str2 = MakeStringConstant(str);
+  using T = decltype(str2);
+  EXPECT_EQ(Callable{}(), T::value);
+  EXPECT_EQ(Callable{}(), str2());
+}
+
+}  // namespace
diff --git a/third_party/abseil_cpp/absl/strings/numbers.cc b/third_party/abseil_cpp/absl/strings/numbers.cc
index 68c26dd6f8c1..3da1059c908d 100644
--- a/third_party/abseil_cpp/absl/strings/numbers.cc
+++ b/third_party/abseil_cpp/absl/strings/numbers.cc
@@ -736,9 +736,18 @@ struct LookupTables {
         X / 35, X / 36,                                                   \
   }
 
+// This kVmaxOverBase is generated with
+//  for (int base = 2; base < 37; ++base) {
+//    absl::uint128 max = std::numeric_limits<absl::uint128>::max();
+//    auto result = max / base;
+//    std::cout << "    MakeUint128(" << absl::Uint128High64(result) << "u, "
+//              << absl::Uint128Low64(result) << "u),\n";
+//  }
+// See https://godbolt.org/z/aneYsb
+//
 // uint128& operator/=(uint128) is not constexpr, so hardcode the resulting
 // array to avoid a static initializer.
-template <>
+template<>
 const uint128 LookupTables<uint128>::kVmaxOverBase[] = {
     0,
     0,
@@ -779,6 +788,111 @@ const uint128 LookupTables<uint128>::kVmaxOverBase[] = {
     MakeUint128(512409557603043100u, 8198552921648689607u),
 };
 
+// This kVmaxOverBase generated with
+//   for (int base = 2; base < 37; ++base) {
+//    absl::int128 max = std::numeric_limits<absl::int128>::max();
+//    auto result = max / base;
+//    std::cout << "\tMakeInt128(" << absl::Int128High64(result) << ", "
+//              << absl::Int128Low64(result) << "u),\n";
+//  }
+// See https://godbolt.org/z/7djYWz
+//
+// int128& operator/=(int128) is not constexpr, so hardcode the resulting array
+// to avoid a static initializer.
+template<>
+const int128 LookupTables<int128>::kVmaxOverBase[] = {
+    0,
+    0,
+    MakeInt128(4611686018427387903, 18446744073709551615u),
+    MakeInt128(3074457345618258602, 12297829382473034410u),
+    MakeInt128(2305843009213693951, 18446744073709551615u),
+    MakeInt128(1844674407370955161, 11068046444225730969u),
+    MakeInt128(1537228672809129301, 6148914691236517205u),
+    MakeInt128(1317624576693539401, 2635249153387078802u),
+    MakeInt128(1152921504606846975, 18446744073709551615u),
+    MakeInt128(1024819115206086200, 16397105843297379214u),
+    MakeInt128(922337203685477580, 14757395258967641292u),
+    MakeInt128(838488366986797800, 13415813871788764811u),
+    MakeInt128(768614336404564650, 12297829382473034410u),
+    MakeInt128(709490156681136600, 11351842506898185609u),
+    MakeInt128(658812288346769700, 10540996613548315209u),
+    MakeInt128(614891469123651720, 9838263505978427528u),
+    MakeInt128(576460752303423487, 18446744073709551615u),
+    MakeInt128(542551296285575047, 9765923333140350855u),
+    MakeInt128(512409557603043100, 8198552921648689607u),
+    MakeInt128(485440633518672410, 17475862806672206794u),
+    MakeInt128(461168601842738790, 7378697629483820646u),
+    MakeInt128(439208192231179800, 7027331075698876806u),
+    MakeInt128(419244183493398900, 6707906935894382405u),
+    MakeInt128(401016175515425035, 2406097053092550210u),
+    MakeInt128(384307168202282325, 6148914691236517205u),
+    MakeInt128(368934881474191032, 5902958103587056517u),
+    MakeInt128(354745078340568300, 5675921253449092804u),
+    MakeInt128(341606371735362066, 17763531330238827482u),
+    MakeInt128(329406144173384850, 5270498306774157604u),
+    MakeInt128(318047311615681924, 7633135478776366185u),
+    MakeInt128(307445734561825860, 4919131752989213764u),
+    MakeInt128(297528130221121800, 4760450083537948804u),
+    MakeInt128(288230376151711743, 18446744073709551615u),
+    MakeInt128(279496122328932600, 4471937957262921603u),
+    MakeInt128(271275648142787523, 14106333703424951235u),
+    MakeInt128(263524915338707880, 4216398645419326083u),
+    MakeInt128(256204778801521550, 4099276460824344803u),
+};
+
+// This kVminOverBase generated with
+//  for (int base = 2; base < 37; ++base) {
+//    absl::int128 min = std::numeric_limits<absl::int128>::min();
+//    auto result = min / base;
+//    std::cout << "\tMakeInt128(" << absl::Int128High64(result) << ", "
+//              << absl::Int128Low64(result) << "u),\n";
+//  }
+//
+// See https://godbolt.org/z/7djYWz
+//
+// int128& operator/=(int128) is not constexpr, so hardcode the resulting array
+// to avoid a static initializer.
+template<>
+const int128 LookupTables<int128>::kVminOverBase[] = {
+    0,
+    0,
+    MakeInt128(-4611686018427387904, 0u),
+    MakeInt128(-3074457345618258603, 6148914691236517206u),
+    MakeInt128(-2305843009213693952, 0u),
+    MakeInt128(-1844674407370955162, 7378697629483820647u),
+    MakeInt128(-1537228672809129302, 12297829382473034411u),
+    MakeInt128(-1317624576693539402, 15811494920322472814u),
+    MakeInt128(-1152921504606846976, 0u),
+    MakeInt128(-1024819115206086201, 2049638230412172402u),
+    MakeInt128(-922337203685477581, 3689348814741910324u),
+    MakeInt128(-838488366986797801, 5030930201920786805u),
+    MakeInt128(-768614336404564651, 6148914691236517206u),
+    MakeInt128(-709490156681136601, 7094901566811366007u),
+    MakeInt128(-658812288346769701, 7905747460161236407u),
+    MakeInt128(-614891469123651721, 8608480567731124088u),
+    MakeInt128(-576460752303423488, 0u),
+    MakeInt128(-542551296285575048, 8680820740569200761u),
+    MakeInt128(-512409557603043101, 10248191152060862009u),
+    MakeInt128(-485440633518672411, 970881267037344822u),
+    MakeInt128(-461168601842738791, 11068046444225730970u),
+    MakeInt128(-439208192231179801, 11419412998010674810u),
+    MakeInt128(-419244183493398901, 11738837137815169211u),
+    MakeInt128(-401016175515425036, 16040647020617001406u),
+    MakeInt128(-384307168202282326, 12297829382473034411u),
+    MakeInt128(-368934881474191033, 12543785970122495099u),
+    MakeInt128(-354745078340568301, 12770822820260458812u),
+    MakeInt128(-341606371735362067, 683212743470724134u),
+    MakeInt128(-329406144173384851, 13176245766935394012u),
+    MakeInt128(-318047311615681925, 10813608594933185431u),
+    MakeInt128(-307445734561825861, 13527612320720337852u),
+    MakeInt128(-297528130221121801, 13686293990171602812u),
+    MakeInt128(-288230376151711744, 0u),
+    MakeInt128(-279496122328932601, 13974806116446630013u),
+    MakeInt128(-271275648142787524, 4340410370284600381u),
+    MakeInt128(-263524915338707881, 14230345428290225533u),
+    MakeInt128(-256204778801521551, 14347467612885206813u),
+};
+
 template <typename IntType>
 const IntType LookupTables<IntType>::kVmaxOverBase[] =
     X_OVER_BASE_INITIALIZER(std::numeric_limits<IntType>::max());
@@ -948,6 +1062,10 @@ bool safe_strto64_base(absl::string_view text, int64_t* value, int base) {
   return safe_int_internal<int64_t>(text, value, base);
 }
 
+bool safe_strto128_base(absl::string_view text, int128* value, int base) {
+  return safe_int_internal<absl::int128>(text, value, base);
+}
+
 bool safe_strtou32_base(absl::string_view text, uint32_t* value, int base) {
   return safe_uint_internal<uint32_t>(text, value, base);
 }
diff --git a/third_party/abseil_cpp/absl/strings/numbers.h b/third_party/abseil_cpp/absl/strings/numbers.h
index d872cca5dc48..2e004b44f887 100644
--- a/third_party/abseil_cpp/absl/strings/numbers.h
+++ b/third_party/abseil_cpp/absl/strings/numbers.h
@@ -127,6 +127,8 @@ inline void PutTwoDigits(size_t i, char* buf) {
 // safe_strto?() functions for implementing SimpleAtoi()
 bool safe_strto32_base(absl::string_view text, int32_t* value, int base);
 bool safe_strto64_base(absl::string_view text, int64_t* value, int base);
+bool safe_strto128_base(absl::string_view text, absl::int128* value,
+                         int base);
 bool safe_strtou32_base(absl::string_view text, uint32_t* value, int base);
 bool safe_strtou64_base(absl::string_view text, uint64_t* value, int base);
 bool safe_strtou128_base(absl::string_view text, absl::uint128* value,
@@ -256,6 +258,11 @@ ABSL_MUST_USE_RESULT bool SimpleAtoi(absl::string_view str, int_type* out) {
 }
 
 ABSL_MUST_USE_RESULT inline bool SimpleAtoi(absl::string_view str,
+                                            absl::int128* out) {
+  return numbers_internal::safe_strto128_base(str, out, 10);
+}
+
+ABSL_MUST_USE_RESULT inline bool SimpleAtoi(absl::string_view str,
                                             absl::uint128* out) {
   return numbers_internal::safe_strtou128_base(str, out, 10);
 }
diff --git a/third_party/abseil_cpp/absl/strings/numbers_test.cc b/third_party/abseil_cpp/absl/strings/numbers_test.cc
index 7db85e754da7..4ab67fb669be 100644
--- a/third_party/abseil_cpp/absl/strings/numbers_test.cc
+++ b/third_party/abseil_cpp/absl/strings/numbers_test.cc
@@ -251,7 +251,7 @@ TEST(Numbers, TestFastPrints) {
 template <typename int_type, typename in_val_type>
 void VerifySimpleAtoiGood(in_val_type in_value, int_type exp_value) {
   std::string s;
-  // uint128 can be streamed but not StrCat'd
+  // (u)int128 can be streamed but not StrCat'd.
   absl::strings_internal::OStringStream(&s) << in_value;
   int_type x = static_cast<int_type>(~exp_value);
   EXPECT_TRUE(SimpleAtoi(s, &x))
@@ -264,7 +264,9 @@ void VerifySimpleAtoiGood(in_val_type in_value, int_type exp_value) {
 
 template <typename int_type, typename in_val_type>
 void VerifySimpleAtoiBad(in_val_type in_value) {
-  std::string s = absl::StrCat(in_value);
+  std::string s;
+  // (u)int128 can be streamed but not StrCat'd.
+  absl::strings_internal::OStringStream(&s) << in_value;
   int_type x;
   EXPECT_FALSE(SimpleAtoi(s, &x));
   EXPECT_FALSE(SimpleAtoi(s.c_str(), &x));
@@ -347,6 +349,31 @@ TEST(NumbersTest, Atoi) {
       std::numeric_limits<absl::uint128>::max(),
       std::numeric_limits<absl::uint128>::max());
 
+  // SimpleAtoi(absl::string_view, absl::int128)
+  VerifySimpleAtoiGood<absl::int128>(0, 0);
+  VerifySimpleAtoiGood<absl::int128>(42, 42);
+  VerifySimpleAtoiGood<absl::int128>(-42, -42);
+
+  VerifySimpleAtoiGood<absl::int128>(std::numeric_limits<int32_t>::min(),
+                                      std::numeric_limits<int32_t>::min());
+  VerifySimpleAtoiGood<absl::int128>(std::numeric_limits<int32_t>::max(),
+                                      std::numeric_limits<int32_t>::max());
+  VerifySimpleAtoiGood<absl::int128>(std::numeric_limits<uint32_t>::max(),
+                                      std::numeric_limits<uint32_t>::max());
+  VerifySimpleAtoiGood<absl::int128>(std::numeric_limits<int64_t>::min(),
+                                      std::numeric_limits<int64_t>::min());
+  VerifySimpleAtoiGood<absl::int128>(std::numeric_limits<int64_t>::max(),
+                                      std::numeric_limits<int64_t>::max());
+  VerifySimpleAtoiGood<absl::int128>(std::numeric_limits<uint64_t>::max(),
+                                      std::numeric_limits<uint64_t>::max());
+  VerifySimpleAtoiGood<absl::int128>(
+      std::numeric_limits<absl::int128>::min(),
+      std::numeric_limits<absl::int128>::min());
+  VerifySimpleAtoiGood<absl::int128>(
+      std::numeric_limits<absl::int128>::max(),
+      std::numeric_limits<absl::int128>::max());
+  VerifySimpleAtoiBad<absl::int128>(std::numeric_limits<absl::uint128>::max());
+
   // Some other types
   VerifySimpleAtoiGood<int>(-42, -42);
   VerifySimpleAtoiGood<int32_t>(-42, -42);
@@ -359,6 +386,12 @@ TEST(NumbersTest, Atoi) {
   VerifySimpleAtoiGood<std::string::size_type>(42, 42);
 }
 
+TEST(NumbersTest, Atod) {
+  double d;
+  EXPECT_TRUE(absl::SimpleAtod("nan", &d));
+  EXPECT_TRUE(std::isnan(d));
+}
+
 TEST(NumbersTest, Atoenum) {
   enum E01 {
     E01_zero = 0,
@@ -719,6 +752,51 @@ TEST(stringtest, safe_strtou128_random) {
     EXPECT_FALSE(parse_func(s, &parsed_value, base));
   }
 }
+TEST(stringtest, safe_strto128_random) {
+  // random number generators don't work for int128, and
+  // int128 can be streamed but not StrCat'd, so this code must be custom
+  // implemented for int128, but is generally the same as what's above.
+  // test_random_integer_parse_base<absl::int128>(
+  //     &absl::numbers_internal::safe_strto128_base);
+  using RandomEngine = std::minstd_rand0;
+  using IntType = absl::int128;
+  constexpr auto parse_func = &absl::numbers_internal::safe_strto128_base;
+
+  std::random_device rd;
+  RandomEngine rng(rd());
+  std::uniform_int_distribution<int64_t> random_int64(
+      std::numeric_limits<int64_t>::min());
+  std::uniform_int_distribution<uint64_t> random_uint64(
+      std::numeric_limits<uint64_t>::min());
+  std::uniform_int_distribution<int> random_base(2, 35);
+
+  for (size_t i = 0; i < kNumRandomTests; ++i) {
+    int64_t high = random_int64(rng);
+    uint64_t low = random_uint64(rng);
+    IntType value = absl::MakeInt128(high, low);
+
+    int base = random_base(rng);
+    std::string str_value;
+    EXPECT_TRUE(Itoa<IntType>(value, base, &str_value));
+    IntType parsed_value;
+
+    // Test successful parse
+    EXPECT_TRUE(parse_func(str_value, &parsed_value, base));
+    EXPECT_EQ(parsed_value, value);
+
+    // Test overflow
+    std::string s;
+    absl::strings_internal::OStringStream(&s)
+        << std::numeric_limits<IntType>::max() << value;
+    EXPECT_FALSE(parse_func(s, &parsed_value, base));
+
+    // Test underflow
+    s.clear();
+    absl::strings_internal::OStringStream(&s)
+        << std::numeric_limits<IntType>::min() << value;
+    EXPECT_FALSE(parse_func(s, &parsed_value, base));
+  }
+}
 
 TEST(stringtest, safe_strtou32_base) {
   for (int i = 0; strtouint32_test_cases()[i].str != nullptr; ++i) {
diff --git a/third_party/abseil_cpp/absl/strings/str_cat.cc b/third_party/abseil_cpp/absl/strings/str_cat.cc
index d9afe2f38520..dd5d25b0d6df 100644
--- a/third_party/abseil_cpp/absl/strings/str_cat.cc
+++ b/third_party/abseil_cpp/absl/strings/str_cat.cc
@@ -141,12 +141,12 @@ namespace strings_internal {
 std::string CatPieces(std::initializer_list<absl::string_view> pieces) {
   std::string result;
   size_t total_size = 0;
-  for (const absl::string_view piece : pieces) total_size += piece.size();
+  for (const absl::string_view& piece : pieces) total_size += piece.size();
   strings_internal::STLStringResizeUninitialized(&result, total_size);
 
   char* const begin = &result[0];
   char* out = begin;
-  for (const absl::string_view piece : pieces) {
+  for (const absl::string_view& piece : pieces) {
     const size_t this_size = piece.size();
     if (this_size != 0) {
       memcpy(out, piece.data(), this_size);
@@ -170,7 +170,7 @@ void AppendPieces(std::string* dest,
                   std::initializer_list<absl::string_view> pieces) {
   size_t old_size = dest->size();
   size_t total_size = old_size;
-  for (const absl::string_view piece : pieces) {
+  for (const absl::string_view& piece : pieces) {
     ASSERT_NO_OVERLAP(*dest, piece);
     total_size += piece.size();
   }
@@ -178,7 +178,7 @@ void AppendPieces(std::string* dest,
 
   char* const begin = &(*dest)[0];
   char* out = begin + old_size;
-  for (const absl::string_view piece : pieces) {
+  for (const absl::string_view& piece : pieces) {
     const size_t this_size = piece.size();
     if (this_size != 0) {
       memcpy(out, piece.data(), this_size);
diff --git a/third_party/abseil_cpp/absl/strings/str_cat_benchmark.cc b/third_party/abseil_cpp/absl/strings/str_cat_benchmark.cc
index ee4ad112f5d9..02c4dbe6d8f1 100644
--- a/third_party/abseil_cpp/absl/strings/str_cat_benchmark.cc
+++ b/third_party/abseil_cpp/absl/strings/str_cat_benchmark.cc
@@ -137,4 +137,51 @@ void BM_DoubleToString_By_SixDigits(benchmark::State& state) {
 }
 BENCHMARK(BM_DoubleToString_By_SixDigits);
 
+template <typename... Chunks>
+void BM_StrAppendImpl(benchmark::State& state, size_t total_bytes,
+                      Chunks... chunks) {
+  for (auto s : state) {
+    std::string result;
+    while (result.size() < total_bytes) {
+      absl::StrAppend(&result, chunks...);
+      benchmark::DoNotOptimize(result);
+    }
+  }
+}
+
+void BM_StrAppend(benchmark::State& state) {
+  const int total_bytes = state.range(0);
+  const int chunks_at_a_time = state.range(1);
+  const absl::string_view kChunk = "0123456789";
+
+  switch (chunks_at_a_time) {
+    case 1:
+      return BM_StrAppendImpl(state, total_bytes, kChunk);
+    case 2:
+      return BM_StrAppendImpl(state, total_bytes, kChunk, kChunk);
+    case 4:
+      return BM_StrAppendImpl(state, total_bytes, kChunk, kChunk, kChunk,
+                              kChunk);
+    case 8:
+      return BM_StrAppendImpl(state, total_bytes, kChunk, kChunk, kChunk,
+                              kChunk, kChunk, kChunk, kChunk, kChunk);
+    default:
+      std::abort();
+  }
+}
+
+template <typename B>
+void StrAppendConfig(B* benchmark) {
+  for (int bytes : {10, 100, 1000, 10000}) {
+    for (int chunks : {1, 2, 4, 8}) {
+      // Only add the ones that divide properly. Otherwise we are over counting.
+      if (bytes % (10 * chunks) == 0) {
+        benchmark->Args({bytes, chunks});
+      }
+    }
+  }
+}
+
+BENCHMARK(BM_StrAppend)->Apply(StrAppendConfig);
+
 }  // namespace
diff --git a/third_party/abseil_cpp/absl/strings/str_format.h b/third_party/abseil_cpp/absl/strings/str_format.h
index 36bd84a3e60b..01465107e105 100644
--- a/third_party/abseil_cpp/absl/strings/str_format.h
+++ b/third_party/abseil_cpp/absl/strings/str_format.h
@@ -63,6 +63,9 @@
 //     loosely typed. `FormatUntyped()` is not a template and does not perform
 //     any compile-time checking of the format string; instead, it returns a
 //     boolean from a runtime check.
+//
+// In addition, the `str_format` library provides extension points for
+// augmenting formatting to new types.  See "StrFormat Extensions" below.
 
 #ifndef ABSL_STRINGS_STR_FORMAT_H_
 #define ABSL_STRINGS_STR_FORMAT_H_
@@ -278,9 +281,36 @@ using FormatSpec = str_format_internal::FormatSpecTemplate<
 //   } else {
 //     ... error case ...
 //   }
+
+#if defined(__cpp_nontype_template_parameter_auto)
+// If C++17 is available, an 'extended' format is also allowed that can specify
+// multiple conversion characters per format argument, using a combination of
+// `absl::FormatConversionCharSet` enum values (logically a set union)
+//  via the `|` operator. (Single character-based arguments are still accepted,
+// but cannot be combined). Some common conversions also have predefined enum
+// values, such as `absl::FormatConversionCharSet::kIntegral`.
+//
+// Example:
+//   // Extended format supports multiple conversion characters per argument,
+//   // specified via a combination of `FormatConversionCharSet` enums.
+//   using MyFormat = absl::ParsedFormat<absl::FormatConversionCharSet::d |
+//                                       absl::FormatConversionCharSet::x>;
+//   MyFormat GetFormat(bool use_hex) {
+//     if (use_hex) return MyFormat("foo %x bar");
+//     return MyFormat("foo %d bar");
+//   }
+//   // `format` can be used with any value that supports 'd' and 'x',
+//   // like `int`.
+//   auto format = GetFormat(use_hex);
+//   value = StringF(format, i);
+template <auto... Conv>
+using ParsedFormat = absl::str_format_internal::ExtendedParsedFormat<
+    absl::str_format_internal::ToFormatConversionCharSet(Conv)...>;
+#else
 template <char... Conv>
 using ParsedFormat = str_format_internal::ExtendedParsedFormat<
     absl::str_format_internal::ToFormatConversionCharSet(Conv)...>;
+#endif  // defined(__cpp_nontype_template_parameter_auto)
 
 // StrFormat()
 //
@@ -537,6 +567,246 @@ ABSL_MUST_USE_RESULT inline bool FormatUntyped(
       str_format_internal::UntypedFormatSpecImpl::Extract(format), args);
 }
 
+//------------------------------------------------------------------------------
+// StrFormat Extensions
+//------------------------------------------------------------------------------
+//
+// AbslFormatConvert()
+//
+// The StrFormat library provides a customization API for formatting
+// user-defined types using absl::StrFormat(). The API relies on detecting an
+// overload in the user-defined type's namespace of a free (non-member)
+// `AbslFormatConvert()` function, usually as a friend definition with the
+// following signature:
+//
+// absl::FormatConvertResult<...> AbslFormatConvert(
+//     const X& value,
+//     const absl::FormatConversionSpec& spec,
+//     absl::FormatSink *sink);
+//
+// An `AbslFormatConvert()` overload for a type should only be declared in the
+// same file and namespace as said type.
+//
+// The abstractions within this definition include:
+//
+// * An `absl::FormatConversionSpec` to specify the fields to pull from a
+//   user-defined type's format string
+// * An `absl::FormatSink` to hold the converted string data during the
+//   conversion process.
+// * An `absl::FormatConvertResult` to hold the status of the returned
+//   formatting operation
+//
+// The return type encodes all the conversion characters that your
+// AbslFormatConvert() routine accepts.  The return value should be {true}.
+// A return value of {false} will result in `StrFormat()` returning
+// an empty string.  This result will be propagated to the result of
+// `FormatUntyped`.
+//
+// Example:
+//
+// struct Point {
+//   // To add formatting support to `Point`, we simply need to add a free
+//   // (non-member) function `AbslFormatConvert()`.  This method interprets
+//   // `spec` to print in the request format. The allowed conversion characters
+//   // can be restricted via the type of the result, in this example
+//   // string and integral formatting are allowed (but not, for instance
+//   // floating point characters like "%f").  You can add such a free function
+//   // using a friend declaration within the body of the class:
+//   friend absl::FormatConvertResult<absl::FormatConversionCharSet::kString |
+//                                    absl::FormatConversionCharSet::kIntegral>
+//   AbslFormatConvert(const Point& p, const absl::FormatConversionSpec& spec,
+//                     absl::FormatSink* s) {
+//     if (spec.conversion_char() == absl::FormatConversionChar::s) {
+//       s->Append(absl::StrCat("x=", p.x, " y=", p.y));
+//     } else {
+//       s->Append(absl::StrCat(p.x, ",", p.y));
+//     }
+//     return {true};
+//   }
+//
+//   int x;
+//   int y;
+// };
+
+// clang-format off
+
+// FormatConversionChar
+//
+// Specifies the formatting character provided in the format string
+// passed to `StrFormat()`.
+enum class FormatConversionChar : uint8_t {
+  c, s,                    // text
+  d, i, o, u, x, X,        // int
+  f, F, e, E, g, G, a, A,  // float
+  n, p                     // misc
+};
+// clang-format on
+
+// FormatConversionSpec
+//
+// Specifies modifications to the conversion of the format string, through use
+// of one or more format flags in the source format string.
+class FormatConversionSpec {
+ public:
+  // FormatConversionSpec::is_basic()
+  //
+  // Indicates that width and precision are not specified, and no additional
+  // flags are set for this conversion character in the format string.
+  bool is_basic() const { return impl_.is_basic(); }
+
+  // FormatConversionSpec::has_left_flag()
+  //
+  // Indicates whether the result should be left justified for this conversion
+  // character in the format string. This flag is set through use of a '-'
+  // character in the format string. E.g. "%-s"
+  bool has_left_flag() const { return impl_.has_left_flag(); }
+
+  // FormatConversionSpec::has_show_pos_flag()
+  //
+  // Indicates whether a sign column is prepended to the result for this
+  // conversion character in the format string, even if the result is positive.
+  // This flag is set through use of a '+' character in the format string.
+  // E.g. "%+d"
+  bool has_show_pos_flag() const { return impl_.has_show_pos_flag(); }
+
+  // FormatConversionSpec::has_sign_col_flag()
+  //
+  // Indicates whether a mandatory sign column is added to the result for this
+  // conversion character. This flag is set through use of a space character
+  // (' ') in the format string. E.g. "% i"
+  bool has_sign_col_flag() const { return impl_.has_sign_col_flag(); }
+
+  // FormatConversionSpec::has_alt_flag()
+  //
+  // Indicates whether an "alternate" format is applied to the result for this
+  // conversion character. Alternative forms depend on the type of conversion
+  // character, and unallowed alternatives are undefined. This flag is set
+  // through use of a '#' character in the format string. E.g. "%#h"
+  bool has_alt_flag() const { return impl_.has_alt_flag(); }
+
+  // FormatConversionSpec::has_zero_flag()
+  //
+  // Indicates whether zeroes should be prepended to the result for this
+  // conversion character instead of spaces. This flag is set through use of the
+  // '0' character in the format string. E.g. "%0f"
+  bool has_zero_flag() const { return impl_.has_zero_flag(); }
+
+  // FormatConversionSpec::conversion_char()
+  //
+  // Returns the underlying conversion character.
+  FormatConversionChar conversion_char() const {
+    return impl_.conversion_char();
+  }
+
+  // FormatConversionSpec::width()
+  //
+  // Returns the specified width (indicated through use of a non-zero integer
+  // value or '*' character) of the conversion character. If width is
+  // unspecified, it returns a negative value.
+  int width() const { return impl_.width(); }
+
+  // FormatConversionSpec::precision()
+  //
+  // Returns the specified precision (through use of the '.' character followed
+  // by a non-zero integer value or '*' character) of the conversion character.
+  // If precision is unspecified, it returns a negative value.
+  int precision() const { return impl_.precision(); }
+
+ private:
+  explicit FormatConversionSpec(
+      str_format_internal::FormatConversionSpecImpl impl)
+      : impl_(impl) {}
+
+  friend str_format_internal::FormatConversionSpecImpl;
+
+  absl::str_format_internal::FormatConversionSpecImpl impl_;
+};
+
+// Type safe OR operator for FormatConversionCharSet to allow accepting multiple
+// conversion chars in custom format converters.
+constexpr FormatConversionCharSet operator|(FormatConversionCharSet a,
+                                            FormatConversionCharSet b) {
+  return static_cast<FormatConversionCharSet>(static_cast<uint64_t>(a) |
+                                              static_cast<uint64_t>(b));
+}
+
+// FormatConversionCharSet
+//
+// Specifies the _accepted_ conversion types as a template parameter to
+// FormatConvertResult for custom implementations of `AbslFormatConvert`.
+// Note the helper predefined alias definitions (kIntegral, etc.) below.
+enum class FormatConversionCharSet : uint64_t {
+  // text
+  c = str_format_internal::FormatConversionCharToConvInt('c'),
+  s = str_format_internal::FormatConversionCharToConvInt('s'),
+  // integer
+  d = str_format_internal::FormatConversionCharToConvInt('d'),
+  i = str_format_internal::FormatConversionCharToConvInt('i'),
+  o = str_format_internal::FormatConversionCharToConvInt('o'),
+  u = str_format_internal::FormatConversionCharToConvInt('u'),
+  x = str_format_internal::FormatConversionCharToConvInt('x'),
+  X = str_format_internal::FormatConversionCharToConvInt('X'),
+  // Float
+  f = str_format_internal::FormatConversionCharToConvInt('f'),
+  F = str_format_internal::FormatConversionCharToConvInt('F'),
+  e = str_format_internal::FormatConversionCharToConvInt('e'),
+  E = str_format_internal::FormatConversionCharToConvInt('E'),
+  g = str_format_internal::FormatConversionCharToConvInt('g'),
+  G = str_format_internal::FormatConversionCharToConvInt('G'),
+  a = str_format_internal::FormatConversionCharToConvInt('a'),
+  A = str_format_internal::FormatConversionCharToConvInt('A'),
+  // misc
+  n = str_format_internal::FormatConversionCharToConvInt('n'),
+  p = str_format_internal::FormatConversionCharToConvInt('p'),
+
+  // Used for width/precision '*' specification.
+  kStar = static_cast<uint64_t>(
+      absl::str_format_internal::FormatConversionCharSetInternal::kStar),
+  // Some predefined values:
+  kIntegral = d | i | u | o | x | X,
+  kFloating = a | e | f | g | A | E | F | G,
+  kNumeric = kIntegral | kFloating,
+  kString = s,
+  kPointer = p,
+};
+
+// FormatSink
+//
+// An abstraction to which conversions write their string data.
+//
+class FormatSink {
+ public:
+  // Appends `count` copies of `ch`.
+  void Append(size_t count, char ch) { sink_->Append(count, ch); }
+
+  void Append(string_view v) { sink_->Append(v); }
+
+  // Appends the first `precision` bytes of `v`. If this is less than
+  // `width`, spaces will be appended first (if `left` is false), or
+  // after (if `left` is true) to ensure the total amount appended is
+  // at least `width`.
+  bool PutPaddedString(string_view v, int width, int precision, bool left) {
+    return sink_->PutPaddedString(v, width, precision, left);
+  }
+
+ private:
+  friend str_format_internal::FormatSinkImpl;
+  explicit FormatSink(str_format_internal::FormatSinkImpl* s) : sink_(s) {}
+  str_format_internal::FormatSinkImpl* sink_;
+};
+
+// FormatConvertResult
+//
+// Indicates whether a call to AbslFormatConvert() was successful.
+// This return type informs the StrFormat extension framework (through
+// ADL but using the return type) of what conversion characters are supported.
+// It is strongly discouraged to return {false}, as this will result in an
+// empty string in StrFormat.
+template <FormatConversionCharSet C>
+struct FormatConvertResult {
+  bool value;
+};
+
 ABSL_NAMESPACE_END
 }  // namespace absl
 
diff --git a/third_party/abseil_cpp/absl/strings/str_format_test.cc b/third_party/abseil_cpp/absl/strings/str_format_test.cc
index 22cfef66d5d4..c60027ad297d 100644
--- a/third_party/abseil_cpp/absl/strings/str_format_test.cc
+++ b/third_party/abseil_cpp/absl/strings/str_format_test.cc
@@ -1,3 +1,16 @@
+// Copyright 2020 The Abseil Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
 
 #include "absl/strings/str_format.h"
 
@@ -16,7 +29,6 @@ namespace absl {
 ABSL_NAMESPACE_BEGIN
 namespace {
 using str_format_internal::FormatArgImpl;
-using str_format_internal::FormatConversionCharSetInternal;
 
 using FormatEntryPointTest = ::testing::Test;
 
@@ -537,46 +549,90 @@ TEST_F(ParsedFormatTest, SimpleUncheckedIncorrect) {
   EXPECT_FALSE((ParsedFormat<'s', 'd', 'g'>::New(format)));
 }
 
-using absl::str_format_internal::FormatConversionCharSet;
+#if defined(__cpp_nontype_template_parameter_auto)
+
+template <auto T>
+std::true_type IsValidParsedFormatArgTest(ParsedFormat<T>*);
+
+template <auto T>
+std::false_type IsValidParsedFormatArgTest(...);
+
+template <auto T>
+using IsValidParsedFormatArg = decltype(IsValidParsedFormatArgTest<T>(nullptr));
+
+TEST_F(ParsedFormatTest, OnlyValidTypesAllowed) {
+  ASSERT_TRUE(IsValidParsedFormatArg<'c'>::value);
+
+  ASSERT_TRUE(IsValidParsedFormatArg<FormatConversionCharSet::d>::value);
+
+  ASSERT_TRUE(IsValidParsedFormatArg<absl::FormatConversionCharSet::d |
+                                     absl::FormatConversionCharSet::x>::value);
+  ASSERT_TRUE(
+      IsValidParsedFormatArg<absl::FormatConversionCharSet::kIntegral>::value);
+
+  // This is an easy mistake to make, however, this will reduce to an integer
+  // which has no meaning, so we need to ensure it doesn't compile.
+  ASSERT_FALSE(IsValidParsedFormatArg<'x' | 'd'>::value);
+
+  // For now, we disallow construction based on ConversionChar (rather than
+  // CharSet)
+  ASSERT_FALSE(IsValidParsedFormatArg<absl::FormatConversionChar::d>::value);
+}
+
+TEST_F(ParsedFormatTest, ExtendedTyping) {
+  EXPECT_FALSE(ParsedFormat<FormatConversionCharSet::d>::New(""));
+  ASSERT_TRUE(ParsedFormat<absl::FormatConversionCharSet::d>::New("%d"));
+  auto v1 = ParsedFormat<'d', absl::FormatConversionCharSet::s>::New("%d%s");
+  ASSERT_TRUE(v1);
+  auto v2 = ParsedFormat<absl::FormatConversionCharSet::d, 's'>::New("%d%s");
+  ASSERT_TRUE(v2);
+  auto v3 = ParsedFormat<absl::FormatConversionCharSet::d |
+                             absl::FormatConversionCharSet::s,
+                         's'>::New("%d%s");
+  ASSERT_TRUE(v3);
+  auto v4 = ParsedFormat<absl::FormatConversionCharSet::d |
+                             absl::FormatConversionCharSet::s,
+                         's'>::New("%s%s");
+  ASSERT_TRUE(v4);
+}
+#endif
 
 TEST_F(ParsedFormatTest, UncheckedCorrect) {
   auto f =
-      ExtendedParsedFormat<FormatConversionCharSetInternal::d>::New("ABC%dDEF");
+      ExtendedParsedFormat<absl::FormatConversionCharSet::d>::New("ABC%dDEF");
   ASSERT_TRUE(f);
   EXPECT_EQ("[ABC]{d:1$d}[DEF]", SummarizeParsedFormat(*f));
 
   std::string format = "%sFFF%dZZZ%f";
   auto f2 = ExtendedParsedFormat<
-      FormatConversionCharSetInternal::kString,
-      FormatConversionCharSetInternal::d,
-      FormatConversionCharSetInternal::kFloating>::New(format);
+      absl::FormatConversionCharSet::kString, absl::FormatConversionCharSet::d,
+      absl::FormatConversionCharSet::kFloating>::New(format);
 
   ASSERT_TRUE(f2);
   EXPECT_EQ("{s:1$s}[FFF]{d:2$d}[ZZZ]{f:3$f}", SummarizeParsedFormat(*f2));
 
   f2 = ExtendedParsedFormat<
-      FormatConversionCharSetInternal::kString,
-      FormatConversionCharSetInternal::d,
-      FormatConversionCharSetInternal::kFloating>::New("%s %d %f");
+      absl::FormatConversionCharSet::kString, absl::FormatConversionCharSet::d,
+      absl::FormatConversionCharSet::kFloating>::New("%s %d %f");
 
   ASSERT_TRUE(f2);
   EXPECT_EQ("{s:1$s}[ ]{d:2$d}[ ]{f:3$f}", SummarizeParsedFormat(*f2));
 
   auto star =
-      ExtendedParsedFormat<FormatConversionCharSetInternal::kStar,
-                           FormatConversionCharSetInternal::d>::New("%*d");
+      ExtendedParsedFormat<absl::FormatConversionCharSet::kStar,
+                           absl::FormatConversionCharSet::d>::New("%*d");
   ASSERT_TRUE(star);
   EXPECT_EQ("{*d:2$1$*d}", SummarizeParsedFormat(*star));
 
-  auto dollar = ExtendedParsedFormat<
-      FormatConversionCharSetInternal::d,
-      FormatConversionCharSetInternal::s>::New("%2$s %1$d");
+  auto dollar =
+      ExtendedParsedFormat<absl::FormatConversionCharSet::d,
+                           absl::FormatConversionCharSet::s>::New("%2$s %1$d");
   ASSERT_TRUE(dollar);
   EXPECT_EQ("{2$s:2$s}[ ]{1$d:1$d}", SummarizeParsedFormat(*dollar));
   // with reuse
   dollar = ExtendedParsedFormat<
-      FormatConversionCharSetInternal::d,
-      FormatConversionCharSetInternal::s>::New("%2$s %1$d %1$d");
+      absl::FormatConversionCharSet::d,
+      absl::FormatConversionCharSet::s>::New("%2$s %1$d %1$d");
   ASSERT_TRUE(dollar);
   EXPECT_EQ("{2$s:2$s}[ ]{1$d:1$d}[ ]{1$d:1$d}",
             SummarizeParsedFormat(*dollar));
@@ -584,62 +640,61 @@ TEST_F(ParsedFormatTest, UncheckedCorrect) {
 
 TEST_F(ParsedFormatTest, UncheckedIgnoredArgs) {
   EXPECT_FALSE(
-      (ExtendedParsedFormat<FormatConversionCharSetInternal::d,
-                            FormatConversionCharSetInternal::s>::New("ABC")));
+      (ExtendedParsedFormat<absl::FormatConversionCharSet::d,
+                            absl::FormatConversionCharSet::s>::New("ABC")));
   EXPECT_FALSE(
-      (ExtendedParsedFormat<FormatConversionCharSetInternal::d,
-                            FormatConversionCharSetInternal::s>::New("%dABC")));
-  EXPECT_FALSE((ExtendedParsedFormat<
-                FormatConversionCharSetInternal::d,
-                FormatConversionCharSetInternal::s>::New("ABC%2$s")));
+      (ExtendedParsedFormat<absl::FormatConversionCharSet::d,
+                            absl::FormatConversionCharSet::s>::New("%dABC")));
+  EXPECT_FALSE(
+      (ExtendedParsedFormat<absl::FormatConversionCharSet::d,
+                            absl::FormatConversionCharSet::s>::New("ABC%2$s")));
   auto f = ExtendedParsedFormat<
-      FormatConversionCharSetInternal::d,
-      FormatConversionCharSetInternal::s>::NewAllowIgnored("ABC");
+      absl::FormatConversionCharSet::d,
+      absl::FormatConversionCharSet::s>::NewAllowIgnored("ABC");
   ASSERT_TRUE(f);
   EXPECT_EQ("[ABC]", SummarizeParsedFormat(*f));
   f = ExtendedParsedFormat<
-      FormatConversionCharSetInternal::d,
-      FormatConversionCharSetInternal::s>::NewAllowIgnored("%dABC");
+      absl::FormatConversionCharSet::d,
+      absl::FormatConversionCharSet::s>::NewAllowIgnored("%dABC");
   ASSERT_TRUE(f);
   EXPECT_EQ("{d:1$d}[ABC]", SummarizeParsedFormat(*f));
   f = ExtendedParsedFormat<
-      FormatConversionCharSetInternal::d,
-      FormatConversionCharSetInternal::s>::NewAllowIgnored("ABC%2$s");
+      absl::FormatConversionCharSet::d,
+      absl::FormatConversionCharSet::s>::NewAllowIgnored("ABC%2$s");
   ASSERT_TRUE(f);
   EXPECT_EQ("[ABC]{2$s:2$s}", SummarizeParsedFormat(*f));
 }
 
 TEST_F(ParsedFormatTest, UncheckedMultipleTypes) {
-  auto dx = ExtendedParsedFormat<
-      FormatConversionCharSetInternal::d |
-      FormatConversionCharSetInternal::x>::New("%1$d %1$x");
+  auto dx =
+      ExtendedParsedFormat<absl::FormatConversionCharSet::d |
+                           absl::FormatConversionCharSet::x>::New("%1$d %1$x");
   EXPECT_TRUE(dx);
   EXPECT_EQ("{1$d:1$d}[ ]{1$x:1$x}", SummarizeParsedFormat(*dx));
 
-  dx = ExtendedParsedFormat<FormatConversionCharSetInternal::d |
-                            FormatConversionCharSetInternal::x>::New("%1$d");
+  dx = ExtendedParsedFormat<absl::FormatConversionCharSet::d |
+                            absl::FormatConversionCharSet::x>::New("%1$d");
   EXPECT_TRUE(dx);
   EXPECT_EQ("{1$d:1$d}", SummarizeParsedFormat(*dx));
 }
 
 TEST_F(ParsedFormatTest, UncheckedIncorrect) {
-  EXPECT_FALSE(
-      ExtendedParsedFormat<FormatConversionCharSetInternal::d>::New(""));
+  EXPECT_FALSE(ExtendedParsedFormat<absl::FormatConversionCharSet::d>::New(""));
 
-  EXPECT_FALSE(ExtendedParsedFormat<FormatConversionCharSetInternal::d>::New(
+  EXPECT_FALSE(ExtendedParsedFormat<absl::FormatConversionCharSet::d>::New(
       "ABC%dDEF%d"));
 
   std::string format = "%sFFF%dZZZ%f";
   EXPECT_FALSE(
-      (ExtendedParsedFormat<FormatConversionCharSetInternal::s,
-                            FormatConversionCharSetInternal::d,
-                            FormatConversionCharSetInternal::g>::New(format)));
+      (ExtendedParsedFormat<absl::FormatConversionCharSet::s,
+                            absl::FormatConversionCharSet::d,
+                            absl::FormatConversionCharSet::g>::New(format)));
 }
 
 TEST_F(ParsedFormatTest, RegressionMixPositional) {
-  EXPECT_FALSE((ExtendedParsedFormat<
-                FormatConversionCharSetInternal::d,
-                FormatConversionCharSetInternal::o>::New("%1$d %o")));
+  EXPECT_FALSE(
+      (ExtendedParsedFormat<absl::FormatConversionCharSet::d,
+                            absl::FormatConversionCharSet::o>::New("%1$d %o")));
 }
 
 using FormatWrapperTest = ::testing::Test;
@@ -664,6 +719,38 @@ TEST_F(FormatWrapperTest, ParsedFormat) {
 ABSL_NAMESPACE_END
 }  // namespace absl
 
+using FormatExtensionTest = ::testing::Test;
+
+struct Point {
+  friend absl::FormatConvertResult<absl::FormatConversionCharSet::kString |
+                                   absl::FormatConversionCharSet::kIntegral>
+  AbslFormatConvert(const Point& p, const absl::FormatConversionSpec& spec,
+                    absl::FormatSink* s) {
+    if (spec.conversion_char() == absl::FormatConversionChar::s) {
+      s->Append(absl::StrCat("x=", p.x, " y=", p.y));
+    } else {
+      s->Append(absl::StrCat(p.x, ",", p.y));
+    }
+    return {true};
+  }
+
+  int x = 10;
+  int y = 20;
+};
+
+TEST_F(FormatExtensionTest, AbslFormatConvertExample) {
+  Point p;
+  EXPECT_EQ(absl::StrFormat("a %s z", p), "a x=10 y=20 z");
+  EXPECT_EQ(absl::StrFormat("a %d z", p), "a 10,20 z");
+
+  // Typed formatting will fail to compile an invalid format.
+  // StrFormat("%f", p);  // Does not compile.
+  std::string actual;
+  absl::UntypedFormatSpec f1("%f");
+  // FormatUntyped will return false for bad character.
+  EXPECT_FALSE(absl::FormatUntyped(&actual, f1, {absl::FormatArg(p)}));
+}
+
 // Some codegen thunks that we can use to easily dump the generated assembly for
 // different StrFormat calls.
 
diff --git a/third_party/abseil_cpp/absl/strings/str_split.h b/third_party/abseil_cpp/absl/strings/str_split.h
index 1ce17f38aa81..bfbca422a8dc 100644
--- a/third_party/abseil_cpp/absl/strings/str_split.h
+++ b/third_party/abseil_cpp/absl/strings/str_split.h
@@ -369,6 +369,12 @@ struct SkipWhitespace {
   }
 };
 
+template <typename T>
+using EnableSplitIfString =
+    typename std::enable_if<std::is_same<T, std::string>::value ||
+                            std::is_same<T, const std::string>::value,
+                            int>::type;
+
 //------------------------------------------------------------------------------
 //                                  StrSplit()
 //------------------------------------------------------------------------------
@@ -489,22 +495,50 @@ struct SkipWhitespace {
 // Try not to depend on this distinction because the bug may one day be fixed.
 template <typename Delimiter>
 strings_internal::Splitter<
-    typename strings_internal::SelectDelimiter<Delimiter>::type, AllowEmpty>
+    typename strings_internal::SelectDelimiter<Delimiter>::type, AllowEmpty,
+    absl::string_view>
 StrSplit(strings_internal::ConvertibleToStringView text, Delimiter d) {
   using DelimiterType =
       typename strings_internal::SelectDelimiter<Delimiter>::type;
-  return strings_internal::Splitter<DelimiterType, AllowEmpty>(
+  return strings_internal::Splitter<DelimiterType, AllowEmpty,
+                                    absl::string_view>(
+      text.value(), DelimiterType(d), AllowEmpty());
+}
+
+template <typename Delimiter, typename StringType,
+          EnableSplitIfString<StringType> = 0>
+strings_internal::Splitter<
+    typename strings_internal::SelectDelimiter<Delimiter>::type, AllowEmpty,
+    std::string>
+StrSplit(StringType&& text, Delimiter d) {
+  using DelimiterType =
+      typename strings_internal::SelectDelimiter<Delimiter>::type;
+  return strings_internal::Splitter<DelimiterType, AllowEmpty, std::string>(
       std::move(text), DelimiterType(d), AllowEmpty());
 }
 
 template <typename Delimiter, typename Predicate>
 strings_internal::Splitter<
-    typename strings_internal::SelectDelimiter<Delimiter>::type, Predicate>
+    typename strings_internal::SelectDelimiter<Delimiter>::type, Predicate,
+    absl::string_view>
 StrSplit(strings_internal::ConvertibleToStringView text, Delimiter d,
          Predicate p) {
   using DelimiterType =
       typename strings_internal::SelectDelimiter<Delimiter>::type;
-  return strings_internal::Splitter<DelimiterType, Predicate>(
+  return strings_internal::Splitter<DelimiterType, Predicate,
+                                    absl::string_view>(
+      text.value(), DelimiterType(d), std::move(p));
+}
+
+template <typename Delimiter, typename Predicate, typename StringType,
+          EnableSplitIfString<StringType> = 0>
+strings_internal::Splitter<
+    typename strings_internal::SelectDelimiter<Delimiter>::type, Predicate,
+    std::string>
+StrSplit(StringType&& text, Delimiter d, Predicate p) {
+  using DelimiterType =
+      typename strings_internal::SelectDelimiter<Delimiter>::type;
+  return strings_internal::Splitter<DelimiterType, Predicate, std::string>(
       std::move(text), DelimiterType(d), std::move(p));
 }
 
diff --git a/third_party/abseil_cpp/absl/strings/str_split_test.cc b/third_party/abseil_cpp/absl/strings/str_split_test.cc
index fcd58d2ee839..7f7c097faee2 100644
--- a/third_party/abseil_cpp/absl/strings/str_split_test.cc
+++ b/third_party/abseil_cpp/absl/strings/str_split_test.cc
@@ -27,7 +27,7 @@
 
 #include "gmock/gmock.h"
 #include "gtest/gtest.h"
-#include "absl/base/dynamic_annotations.h"  // for RunningOnValgrind
+#include "absl/base/dynamic_annotations.h"
 #include "absl/base/macros.h"
 #include "absl/container/flat_hash_map.h"
 #include "absl/container/node_hash_map.h"
@@ -367,7 +367,7 @@ TEST(SplitIterator, EqualityAsEndCondition) {
 TEST(Splitter, RangeIterators) {
   auto splitter = absl::StrSplit("a,b,c", ',');
   std::vector<absl::string_view> output;
-  for (const absl::string_view p : splitter) {
+  for (const absl::string_view& p : splitter) {
     output.push_back(p);
   }
   EXPECT_THAT(output, ElementsAre("a", "b", "c"));
diff --git a/third_party/abseil_cpp/absl/strings/string_view.h b/third_party/abseil_cpp/absl/strings/string_view.h
index 8a9db8c3d796..5260b5b73f47 100644
--- a/third_party/abseil_cpp/absl/strings/string_view.h
+++ b/third_party/abseil_cpp/absl/strings/string_view.h
@@ -111,6 +111,11 @@ ABSL_NAMESPACE_BEGIN
 // example, when splitting a string, `std::vector<absl::string_view>` is a
 // natural data type for the output.
 //
+// For another example, a Cord is a non-contiguous, potentially very
+// long string-like object.  The Cord class has an interface that iteratively
+// provides string_view objects that point to the successive pieces of a Cord
+// object.
+//
 // When constructed from a source which is NUL-terminated, the `string_view`
 // itself will not include the NUL-terminator unless a specific size (including
 // the NUL) is passed to the constructor. As a result, common idioms that work
@@ -382,6 +387,7 @@ class string_view {
   // Returns a "substring" of the `string_view` (at offset `pos` and length
   // `n`) as another string_view. This function throws `std::out_of_bounds` if
   // `pos > size`.
+  // Use absl::ClippedSubstr if you need a truncating substr operation.
   constexpr string_view substr(size_type pos, size_type n = npos) const {
     return ABSL_PREDICT_FALSE(pos > length_)
                ? (base_internal::ThrowStdOutOfRange(
diff --git a/third_party/abseil_cpp/absl/strings/string_view_test.cc b/third_party/abseil_cpp/absl/strings/string_view_test.cc
index ff31b51e87e8..dcebb1500100 100644
--- a/third_party/abseil_cpp/absl/strings/string_view_test.cc
+++ b/third_party/abseil_cpp/absl/strings/string_view_test.cc
@@ -1177,9 +1177,9 @@ TEST(FindOneCharTest, EdgeCases) {
   EXPECT_EQ(absl::string_view::npos, a.rfind('x'));
 }
 
-#ifndef THREAD_SANITIZER  // Allocates too much memory for tsan.
+#ifndef ABSL_HAVE_THREAD_SANITIZER  // Allocates too much memory for tsan.
 TEST(HugeStringView, TwoPointTwoGB) {
-  if (sizeof(size_t) <= 4 || RunningOnValgrind())
+  if (sizeof(size_t) <= 4)
     return;
   // Try a huge string piece.
   const size_t size = size_t{2200} * 1000 * 1000;
@@ -1191,7 +1191,7 @@ TEST(HugeStringView, TwoPointTwoGB) {
   sp.remove_suffix(2);
   EXPECT_EQ(size - 1 - 2, sp.length());
 }
-#endif  // THREAD_SANITIZER
+#endif  // ABSL_HAVE_THREAD_SANITIZER
 
 #if !defined(NDEBUG) && !defined(ABSL_USES_STD_STRING_VIEW)
 TEST(NonNegativeLenTest, NonNegativeLen) {
author	Vincent Ambo <mail@tazj.in>	2020-11-21T13·43+0100
committer	Vincent Ambo <mail@tazj.in>	2020-11-21T14·48+0100
commit	082c006c04343a78d87b6c6ab3608c25d6213c3f (patch)
tree	16e6f04f8d1d1d2d67e8e917d5e7bb48c1b60375 /third_party/abseil_cpp/absl/strings
parent	cc27324d0226953943f408ce3c69ad7d648e005e (diff)