5 files changed, 31 insertions, 10 deletions
diff --git a/absl/strings/cord.cc b/absl/strings/cord.cc
index 1c03a618..1aea396f 100644
--- a/absl/strings/cord.cc
+++ b/absl/strings/cord.cc
@@ -491,7 +491,7 @@ static bool RepMemoryUsageLeaf(const CordRep* rep, size_t* total_mem_usage) {
 }
 
 void Cord::InlineRep::AssignSlow(const Cord::InlineRep& src) {
-  ClearSlow();
+  UnrefTree();
 
   data_ = src.data_;
   if (is_tree()) {
@@ -501,11 +501,10 @@ void Cord::InlineRep::AssignSlow(const Cord::InlineRep& src) {
   }
 }
 
-void Cord::InlineRep::ClearSlow() {
+void Cord::InlineRep::UnrefTree() {
   if (is_tree()) {
     CordRep::Unref(tree());
   }
-  ResetToEmpty();
 }
 
 // --------------------------------------------------------------------
diff --git a/absl/strings/cord.h b/absl/strings/cord.h
index fa9cb913..cb2ffc5c 100644
--- a/absl/strings/cord.h
+++ b/absl/strings/cord.h
@@ -776,8 +776,8 @@ class Cord {
     friend class Cord;
 
     void AssignSlow(const InlineRep& src);
-    // Unrefs the tree, stops profiling, and zeroes the contents
-    void ClearSlow();
+    // Unrefs the tree and stops profiling.
+    void UnrefTree();
 
     void ResetToEmpty() { data_ = {}; }
 
@@ -966,7 +966,7 @@ inline Cord::InlineRep& Cord::InlineRep::operator=(const Cord::InlineRep& src) {
 inline Cord::InlineRep& Cord::InlineRep::operator=(
     Cord::InlineRep&& src) noexcept {
   if (is_tree()) {
-    ClearSlow();
+    UnrefTree();
   }
   data_ = src.data_;
   src.ResetToEmpty();
diff --git a/absl/strings/cord_test.cc b/absl/strings/cord_test.cc
index fb673411..710a1b40 100644
--- a/absl/strings/cord_test.cc
+++ b/absl/strings/cord_test.cc
@@ -1316,6 +1316,26 @@ TEST(Cord, Concat_Append) {
   EXPECT_EQ(s2.size(), size + 1);
 }
 
+TEST(Cord, DiabolicalGrowth) {
+  // This test exercises a diabolical Append(<one char>) on a cord, making the
+  // cord shared before each Append call resulting in a terribly fragmented
+  // resulting cord.
+  // TODO(b/183983616): Apply some minimum compaction when copying a shared
+  // source cord into a mutable copy for updates in CordRepRing.
+  RandomEngine rng(testing::GTEST_FLAG(random_seed));
+  const std::string expected = RandomLowercaseString(&rng, 5000);
+  absl::Cord cord;
+  for (char c : expected) {
+    absl::Cord shared(cord);
+    cord.Append(absl::string_view(&c, 1));
+  }
+  std::string value;
+  absl::CopyCordToString(cord, &value);
+  EXPECT_EQ(value, expected);
+  ABSL_RAW_LOG(INFO, "Diabolical size allocated = %zu",
+               cord.EstimatedMemoryUsage());
+}
+
 TEST(MakeFragmentedCord, MakeFragmentedCordFromInitializerList) {
   absl::Cord fragmented =
       absl::MakeFragmentedCord({"A ", "fragmented ", "Cord"});
diff --git a/absl/strings/internal/cord_rep_ring.cc b/absl/strings/internal/cord_rep_ring.cc
index 4d31d1d9..cb95b19a 100644
--- a/absl/strings/internal/cord_rep_ring.cc
+++ b/absl/strings/internal/cord_rep_ring.cc
@@ -400,10 +400,11 @@ CordRepRing* CordRepRing::Mutable(CordRepRing* rep, size_t extra) {
   // Get current number of entries, and check for max capacity.
   size_t entries = rep->entries();
 
-  size_t min_extra = (std::max)(extra, rep->capacity() * 2 - entries);
   if (!rep->refcount.IsOne()) {
-    return Copy(rep, rep->head(), rep->tail(), min_extra);
+    return Copy(rep, rep->head(), rep->tail(), extra);
   } else if (entries + extra > rep->capacity()) {
+    const size_t min_grow = rep->capacity() + rep->capacity() / 2;
+    const size_t min_extra = (std::max)(extra, min_grow - entries);
     CordRepRing* newrep = CordRepRing::New(entries, min_extra);
     newrep->Fill<false>(rep, rep->head(), rep->tail());
     CordRepRing::Delete(rep);
diff --git a/absl/strings/string_view.h b/absl/strings/string_view.h
index b276bdba..1f14a758 100644
--- a/absl/strings/string_view.h
+++ b/absl/strings/string_view.h
@@ -36,6 +36,7 @@
 #include <limits>
 #include <string>
 
+#include "absl/base/attributes.h"
 #include "absl/base/config.h"
 #include "absl/base/internal/throw_delegate.h"
 #include "absl/base/macros.h"
@@ -180,8 +181,8 @@ class string_view {
 
   template <typename Allocator>
   string_view(  // NOLINT(runtime/explicit)
-      const std::basic_string<char, std::char_traits<char>, Allocator>&
-          str) noexcept
+      const std::basic_string<char, std::char_traits<char>, Allocator>& str
+          ABSL_ATTRIBUTE_LIFETIME_BOUND) noexcept
       // This is implemented in terms of `string_view(p, n)` so `str.size()`
       // doesn't need to be reevaluated after `ptr_` is set.
       : string_view(str.data(), str.size()) {}