Export of internal Abseil changes

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751781aa5b9e998f84a8a7e00789c80d3338730e by Abseil Team <absl-team@google.com>:

Fix attributes.h compilation with -Wundef flag in C

PiperOrigin-RevId: 347394915

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66070a8166b0e1a61236b954d07fbb378f4f990b by Abseil Team <absl-team@google.com>:

Revert the usage of variant<> in Cord iterator and reader.

The introduction of the variant may lead to some missed compiler optimizations.

PiperOrigin-RevId: 347384869
GitOrigin-RevId: 751781aa5b9e998f84a8a7e00789c80d3338730e
Change-Id: Ibf1190d498a6f968f2ea9b89467ccfb5224dafa8

1 files changed, 4 insertions, 7 deletions

diff --git a/absl/strings/cord.cc b/absl/strings/cord.cc
index f87f4882..8d51c750 100644
--- a/absl/strings/cord.cc
+++ b/absl/strings/cord.cc
@@ -1299,8 +1299,7 @@ void Cord::CopyToArraySlowPath(char* dst) const {
 }
 
 Cord::ChunkIterator& Cord::ChunkIterator::AdvanceStack() {
-  assert(absl::holds_alternative<Stack>(context_));
-  auto& stack_of_right_children = absl::get<Stack>(context_);
+  auto& stack_of_right_children = stack_of_right_children_;
   if (stack_of_right_children.empty()) {
     assert(!current_chunk_.empty());  // Called on invalid iterator.
     // We have reached the end of the Cord.
@@ -1357,8 +1356,7 @@ Cord Cord::ChunkIterator::AdvanceAndReadBytes(size_t n) {
     }
     return subcord;
   }
-  assert(absl::holds_alternative<Stack>(context_));
-  auto& stack_of_right_children = absl::get<Stack>(context_);
+  auto& stack_of_right_children = stack_of_right_children_;
   if (n < current_chunk_.size()) {
     // Range to read is a proper subrange of the current chunk.
     assert(current_leaf_ != nullptr);
@@ -1461,7 +1459,7 @@ void Cord::ChunkIterator::AdvanceBytesSlowPath(size_t n) {
   n -= current_chunk_.size();
   bytes_remaining_ -= current_chunk_.size();
 
-  if (!absl::holds_alternative<Stack>(context_)) {
+  if (stack_of_right_children_.empty()) {
     // We have reached the end of the Cord.
     assert(bytes_remaining_ == 0);
     return;
@@ -1470,8 +1468,7 @@ void Cord::ChunkIterator::AdvanceBytesSlowPath(size_t n) {
   // Process the next node(s) on the stack, skipping whole subtrees depending on
   // their length and how many bytes we are advancing.
   CordRep* node = nullptr;
-  assert(absl::holds_alternative<Stack>(context_));
-  auto& stack_of_right_children = absl::get<Stack>(context_);
+  auto& stack_of_right_children = stack_of_right_children_;
   while (!stack_of_right_children.empty()) {
     node = stack_of_right_children.back();
     stack_of_right_children.pop_back();