diff --git a/CMake/AbseilHelpers.cmake b/CMake/AbseilHelpers.cmake
index 9e1772bb5..b114b297c 100644
--- a/CMake/AbseilHelpers.cmake
+++ b/CMake/AbseilHelpers.cmake
@@ -74,12 +74,13 @@ function(absl_header_library)
 
   if(NOT EXISTS ${__dummy_header_only_lib_file})
     file(WRITE ${__dummy_header_only_lib_file}
-      "\
-       /* generated file for header-only cmake target */ \
-       \
-       // single meaningless symbol \
-       void __${_NAME}__header_fakesym() {} \
-       \
+      "/* generated file for header-only cmake target */
+
+      namespace absl {
+
+       // single meaningless symbol
+       void ${_NAME}__header_fakesym() {}
+      }  // namespace absl
       "
     )
   endif()
diff --git a/absl/base/BUILD.bazel b/absl/base/BUILD.bazel
index 64057f6c9..e52846334 100644
--- a/absl/base/BUILD.bazel
+++ b/absl/base/BUILD.bazel
@@ -238,6 +238,7 @@ cc_library(
     deps = [
         ":config",
         ":pretty_function",
+        "//absl/memory",
         "//absl/meta:type_traits",
         "//absl/strings",
         "@com_google_googletest//:gtest",
diff --git a/absl/base/exception_safety_testing_test.cc b/absl/base/exception_safety_testing_test.cc
index 365732c67..c1b5df265 100644
--- a/absl/base/exception_safety_testing_test.cc
+++ b/absl/base/exception_safety_testing_test.cc
@@ -14,10 +14,6 @@ namespace absl {
 namespace {
 using ::absl::exceptions_internal::TestException;
 
-void SetCountdown() { exceptions_internal::countdown = 0; }
-
-void UnsetCountdown() { exceptions_internal::countdown = -1; }
-
 // EXPECT_NO_THROW can't inspect the thrown inspection in general.
 template <typename F>
 void ExpectNoThrow(const F& f) {
@@ -395,12 +391,15 @@ struct FailsBasicGuarantee {
     ++i;
   }
 
-  bool operator!=(const FailsBasicGuarantee& other) const {
+  bool operator==(const FailsBasicGuarantee& other) const {
     return i != other.i;
   }
 
-  friend bool AbslCheckInvariants(const FailsBasicGuarantee& g) {
-    return g.i >= 0;
+  friend testing::AssertionResult AbslCheckInvariants(
+      const FailsBasicGuarantee& g) {
+    if (g.i >= 0) return testing::AssertionSuccess();
+    return testing::AssertionFailure()
+           << "i should be non-negative but is " << g.i;
   }
 
   int i = 0;
@@ -408,7 +407,7 @@ struct FailsBasicGuarantee {
 
 TEST(ExceptionCheckTest, BasicGuaranteeFailure) {
   FailsBasicGuarantee g;
-  EXPECT_FALSE(TestBasicGuarantee(&g, CallOperator{}));
+  EXPECT_FALSE(TestExceptionSafety(&g, CallOperator{}));
 }
 
 struct FollowsBasicGuarantee {
@@ -417,12 +416,15 @@ struct FollowsBasicGuarantee {
     ThrowingValue<> bomb;
   }
 
-  bool operator!=(const FollowsBasicGuarantee& other) const {
-    return i != other.i;
+  bool operator==(const FollowsBasicGuarantee& other) const {
+    return i == other.i;
   }
 
-  friend bool AbslCheckInvariants(const FollowsBasicGuarantee& g) {
-    return g.i >= 0;
+  friend testing::AssertionResult AbslCheckInvariants(
+      const FollowsBasicGuarantee& g) {
+    if (g.i >= 0) return testing::AssertionSuccess();
+    return testing::AssertionFailure()
+           << "i should be non-negative but is " << g.i;
   }
 
   int i = 0;
@@ -430,30 +432,79 @@ struct FollowsBasicGuarantee {
 
 TEST(ExceptionCheckTest, BasicGuarantee) {
   FollowsBasicGuarantee g;
-  EXPECT_TRUE(TestBasicGuarantee(&g, CallOperator{}));
+  EXPECT_TRUE(TestExceptionSafety(&g, CallOperator{}));
 }
 
 TEST(ExceptionCheckTest, StrongGuaranteeFailure) {
   {
     FailsBasicGuarantee g;
-    EXPECT_FALSE(TestStrongGuarantee(&g, CallOperator{}));
+    EXPECT_FALSE(TestExceptionSafety(&g, CallOperator{}, StrongGuarantee(g)));
   }
 
   {
     FollowsBasicGuarantee g;
-    EXPECT_FALSE(TestStrongGuarantee(&g, CallOperator{}));
+    EXPECT_FALSE(TestExceptionSafety(&g, CallOperator{}, StrongGuarantee(g)));
+  }
+}
+
+struct BasicGuaranteeWithExtraInvariants {
+  // After operator(), i is incremented.  If operator() throws, i is set to 9999
+  void operator()() {
+    int old_i = i;
+    i = kExceptionSentinel;
+    ThrowingValue<> bomb;
+    i = ++old_i;
+  }
+
+  bool operator==(const FollowsBasicGuarantee& other) const {
+    return i == other.i;
+  }
+
+  friend testing::AssertionResult AbslCheckInvariants(
+      const BasicGuaranteeWithExtraInvariants& g) {
+    if (g.i >= 0) return testing::AssertionSuccess();
+    return testing::AssertionFailure()
+           << "i should be non-negative but is " << g.i;
+  }
+
+  int i = 0;
+  static constexpr int kExceptionSentinel = 9999;
+};
+constexpr int BasicGuaranteeWithExtraInvariants::kExceptionSentinel;
+
+TEST(ExceptionCheckTest, BasicGuaranteeWithInvariants) {
+  {
+    BasicGuaranteeWithExtraInvariants g;
+    EXPECT_TRUE(TestExceptionSafety(&g, CallOperator{}));
+  }
+
+  {
+    BasicGuaranteeWithExtraInvariants g;
+    EXPECT_TRUE(TestExceptionSafety(
+        &g, CallOperator{}, [](const BasicGuaranteeWithExtraInvariants& w) {
+          if (w.i == BasicGuaranteeWithExtraInvariants::kExceptionSentinel) {
+            return testing::AssertionSuccess();
+          }
+          return testing::AssertionFailure()
+                 << "i should be "
+                 << BasicGuaranteeWithExtraInvariants::kExceptionSentinel
+                 << ", but is " << w.i;
+        }));
   }
 }
 
 struct FollowsStrongGuarantee {
   void operator()() { ThrowingValue<> bomb; }
 
-  bool operator!=(const FollowsStrongGuarantee& other) const {
-    return i != other.i;
+  bool operator==(const FollowsStrongGuarantee& other) const {
+    return i == other.i;
   }
 
-  friend bool AbslCheckInvariants(const FollowsStrongGuarantee& g) {
-    return g.i >= 0;
+  friend testing::AssertionResult AbslCheckInvariants(
+      const FollowsStrongGuarantee& g) {
+    if (g.i >= 0) return testing::AssertionSuccess();
+    return testing::AssertionFailure()
+           << "i should be non-negative but is " << g.i;
   }
 
   int i = 0;
@@ -461,8 +512,65 @@ struct FollowsStrongGuarantee {
 
 TEST(ExceptionCheckTest, StrongGuarantee) {
   FollowsStrongGuarantee g;
-  EXPECT_TRUE(TestBasicGuarantee(&g, CallOperator{}));
-  EXPECT_TRUE(TestStrongGuarantee(&g, CallOperator{}));
+  EXPECT_TRUE(TestExceptionSafety(&g, CallOperator{}));
+  EXPECT_TRUE(TestExceptionSafety(&g, CallOperator{}, StrongGuarantee(g)));
+}
+
+struct NonCopyable {
+  NonCopyable(const NonCopyable&) = delete;
+  explicit NonCopyable(int ii) : i(ii) {}
+
+  void operator()() { ThrowingValue<> bomb; }
+
+  bool operator==(const NonCopyable& other) const { return i == other.i; }
+
+  friend testing::AssertionResult AbslCheckInvariants(const NonCopyable& g) {
+    if (g.i >= 0) return testing::AssertionSuccess();
+    return testing::AssertionFailure()
+           << "i should be non-negative but is " << g.i;
+  }
+
+  int i;
+};
+
+TEST(ExceptionCheckTest, NonCopyable) {
+  NonCopyable g(0);
+  EXPECT_TRUE(TestExceptionSafety(&g, CallOperator{}));
+  EXPECT_TRUE(TestExceptionSafety(
+      &g, CallOperator{},
+      PointeeStrongGuarantee(absl::make_unique<NonCopyable>(g.i))));
+}
+
+struct NonEqualityComparable {
+  void operator()() { ThrowingValue<> bomb; }
+
+  void ModifyOnThrow() {
+    ++i;
+    ThrowingValue<> bomb;
+    static_cast<void>(bomb);
+    --i;
+  }
+
+  friend testing::AssertionResult AbslCheckInvariants(
+      const NonEqualityComparable& g) {
+    if (g.i >= 0) return testing::AssertionSuccess();
+    return testing::AssertionFailure()
+           << "i should be non-negative but is " << g.i;
+  }
+
+  int i = 0;
+};
+
+TEST(ExceptionCheckTest, NonEqualityComparable) {
+  NonEqualityComparable g;
+  auto comp = [](const NonEqualityComparable& a,
+                 const NonEqualityComparable& b) { return a.i == b.i; };
+  EXPECT_TRUE(TestExceptionSafety(&g, CallOperator{}));
+  EXPECT_TRUE(
+      TestExceptionSafety(&g, CallOperator{}, absl::StrongGuarantee(g, comp)));
+  EXPECT_FALSE(TestExceptionSafety(
+      &g, [&](NonEqualityComparable* n) { n->ModifyOnThrow(); },
+      absl::StrongGuarantee(g, comp)));
 }
 
 template <typename T>
@@ -480,11 +588,14 @@ struct InstructionCounter {
     ++counter;
   }
 
-  bool operator!=(const InstructionCounter<ThrowingValue<>>& other) const {
-    return false;
+  bool operator==(const InstructionCounter<ThrowingValue<>>&) const {
+    return true;
   }
 
-  friend bool AbslCheckInvariants(const InstructionCounter&) { return true; }
+  friend testing::AssertionResult AbslCheckInvariants(
+      const InstructionCounter&) {
+    return testing::AssertionSuccess();
+  }
 
   static int counter;
 };
@@ -493,18 +604,38 @@ int InstructionCounter<T>::counter = 0;
 
 TEST(ExceptionCheckTest, Exhaustiveness) {
   InstructionCounter<int> int_factory;
-  EXPECT_TRUE(TestBasicGuarantee(&int_factory, CallOperator{}));
+  EXPECT_TRUE(TestExceptionSafety(&int_factory, CallOperator{}));
   EXPECT_EQ(InstructionCounter<int>::counter, 4);
 
   InstructionCounter<ThrowingValue<>> bomb_factory;
-  EXPECT_TRUE(TestBasicGuarantee(&bomb_factory, CallOperator{}));
+  EXPECT_TRUE(TestExceptionSafety(&bomb_factory, CallOperator{}));
   EXPECT_EQ(InstructionCounter<ThrowingValue<>>::counter, 10);
 
   InstructionCounter<ThrowingValue<>>::counter = 0;
-  EXPECT_TRUE(TestStrongGuarantee(&bomb_factory, CallOperator{}));
+  EXPECT_TRUE(TestExceptionSafety(&bomb_factory, CallOperator{},
+                                  StrongGuarantee(bomb_factory)));
   EXPECT_EQ(InstructionCounter<ThrowingValue<>>::counter, 10);
 }
 
+struct LeaksIfCtorThrows : private exceptions_internal::TrackedObject {
+  LeaksIfCtorThrows() : TrackedObject(ABSL_PRETTY_FUNCTION) {
+    ++counter;
+    ThrowingValue<> v;
+    static_cast<void>(v);
+    --counter;
+  }
+  LeaksIfCtorThrows(const LeaksIfCtorThrows&) noexcept
+      : TrackedObject(ABSL_PRETTY_FUNCTION) {}
+  static int counter;
+};
+int LeaksIfCtorThrows::counter = 0;
+
+TEST(ExceptionCheckTest, TestLeakyCtor) {
+  absl::TestThrowingCtor<LeaksIfCtorThrows>();
+  EXPECT_EQ(LeaksIfCtorThrows::counter, 1);
+  LeaksIfCtorThrows::counter = 0;
+}
+
 struct Tracked : private exceptions_internal::TrackedObject {
   Tracked() : TrackedObject(ABSL_PRETTY_FUNCTION) {}
 };
diff --git a/absl/base/internal/exception_safety_testing.cc b/absl/base/internal/exception_safety_testing.cc
index 383c9c595..32d904ed2 100644
--- a/absl/base/internal/exception_safety_testing.cc
+++ b/absl/base/internal/exception_safety_testing.cc
@@ -4,6 +4,7 @@
 #include "absl/meta/type_traits.h"
 
 namespace absl {
+exceptions_internal::NoThrowTag no_throw_ctor;
 namespace exceptions_internal {
 
 int countdown = -1;
@@ -14,8 +15,7 @@ void MaybeThrow(absl::string_view msg) {
 
 testing::AssertionResult FailureMessage(const TestException& e,
                                         int countdown) noexcept {
-  return testing::AssertionFailure()
-         << "Exception number " << countdown + 1 << " thrown from " << e.what();
+  return testing::AssertionFailure() << "Exception thrown from " << e.what();
 }
 }  // namespace exceptions_internal
 }  // namespace absl
diff --git a/absl/base/internal/exception_safety_testing.h b/absl/base/internal/exception_safety_testing.h
index d2742456f..a0a70d91d 100644
--- a/absl/base/internal/exception_safety_testing.h
+++ b/absl/base/internal/exception_safety_testing.h
@@ -6,6 +6,7 @@
 #include <cstddef>
 #include <cstdint>
 #include <functional>
+#include <initializer_list>
 #include <iosfwd>
 #include <string>
 #include <unordered_map>
@@ -13,6 +14,7 @@
 #include "gtest/gtest.h"
 #include "absl/base/config.h"
 #include "absl/base/internal/pretty_function.h"
+#include "absl/memory/memory.h"
 #include "absl/meta/type_traits.h"
 #include "absl/strings/string_view.h"
 #include "absl/strings/substitute.h"
@@ -43,6 +45,8 @@ constexpr NoThrow operator&(NoThrow a, NoThrow b) {
 }
 
 namespace exceptions_internal {
+struct NoThrowTag {};
+
 constexpr bool ThrowingAllowed(NoThrow flags, NoThrow flag) {
   return !static_cast<bool>(flags & flag);
 }
@@ -92,8 +96,46 @@ class TrackedObject {
 
   friend struct ::absl::AllocInspector;
 };
+
+template <typename T, typename... Checkers>
+testing::AssertionResult TestInvariants(const T& t, const TestException& e,
+                                        int count,
+                                        const Checkers&... checkers) {
+  auto out = AbslCheckInvariants(t);
+  // Don't bother with the checkers if the class invariants are already broken.
+  bool dummy[] = {true,
+                  (out && (out = testing::AssertionResult(checkers(t))))...};
+  static_cast<void>(dummy);
+
+  return out ? out
+             : out << " Caused by exception " << count << "thrown by "
+                   << e.what();
+}
+
+template <typename T, typename EqualTo>
+class StrongGuaranteeTester {
+ public:
+  explicit StrongGuaranteeTester(std::unique_ptr<T> t_ptr, EqualTo eq) noexcept
+      : val_(std::move(t_ptr)), eq_(eq) {}
+
+  testing::AssertionResult operator()(const T& other) const {
+    return eq_(*val_, other) ? testing::AssertionSuccess()
+                             : testing::AssertionFailure() << "State changed";
+  }
+
+ private:
+  std::unique_ptr<T> val_;
+  EqualTo eq_;
+};
 }  // namespace exceptions_internal
 
+extern exceptions_internal::NoThrowTag no_throw_ctor;
+
+// These are useful for tests which just construct objects and make sure there
+// are no leaks.
+inline void SetCountdown() { exceptions_internal::countdown = 0; }
+inline void UnsetCountdown() { exceptions_internal::countdown = -1; }
+
 // A test class which is contextually convertible to bool.  The conversion can
 // be instrumented to throw at a controlled time.
 class ThrowingBool {
@@ -152,6 +194,9 @@ class ThrowingValue : private exceptions_internal::TrackedObject {
     dummy_ = i;
   }
 
+  ThrowingValue(int i, exceptions_internal::NoThrowTag) noexcept
+      : TrackedObject(ABSL_PRETTY_FUNCTION), dummy_(i) {}
+
   // absl expects nothrow destructors
   ~ThrowingValue() noexcept = default;
 
@@ -173,22 +218,22 @@ class ThrowingValue : private exceptions_internal::TrackedObject {
   // Arithmetic Operators
   ThrowingValue operator+(const ThrowingValue& other) const {
     exceptions_internal::MaybeThrow(ABSL_PRETTY_FUNCTION);
-    return ThrowingValue(dummy_ + other.dummy_, NoThrowTag{});
+    return ThrowingValue(dummy_ + other.dummy_, no_throw_ctor);
   }
 
   ThrowingValue operator+() const {
     exceptions_internal::MaybeThrow(ABSL_PRETTY_FUNCTION);
-    return ThrowingValue(dummy_, NoThrowTag{});
+    return ThrowingValue(dummy_, no_throw_ctor);
   }
 
   ThrowingValue operator-(const ThrowingValue& other) const {
     exceptions_internal::MaybeThrow(ABSL_PRETTY_FUNCTION);
-    return ThrowingValue(dummy_ - other.dummy_, NoThrowTag{});
+    return ThrowingValue(dummy_ - other.dummy_, no_throw_ctor);
   }
 
   ThrowingValue operator-() const {
     exceptions_internal::MaybeThrow(ABSL_PRETTY_FUNCTION);
-    return ThrowingValue(-dummy_, NoThrowTag{});
+    return ThrowingValue(-dummy_, no_throw_ctor);
   }
 
   ThrowingValue& operator++() {
@@ -199,7 +244,7 @@ class ThrowingValue : private exceptions_internal::TrackedObject {
 
   ThrowingValue operator++(int) {
     exceptions_internal::MaybeThrow(ABSL_PRETTY_FUNCTION);
-    auto out = ThrowingValue(dummy_, NoThrowTag{});
+    auto out = ThrowingValue(dummy_, no_throw_ctor);
     ++dummy_;
     return out;
   }
@@ -212,34 +257,34 @@ class ThrowingValue : private exceptions_internal::TrackedObject {
 
   ThrowingValue operator--(int) {
     exceptions_internal::MaybeThrow(ABSL_PRETTY_FUNCTION);
-    auto out = ThrowingValue(dummy_, NoThrowTag{});
+    auto out = ThrowingValue(dummy_, no_throw_ctor);
     --dummy_;
     return out;
   }
 
   ThrowingValue operator*(const ThrowingValue& other) const {
     exceptions_internal::MaybeThrow(ABSL_PRETTY_FUNCTION);
-    return ThrowingValue(dummy_ * other.dummy_, NoThrowTag{});
+    return ThrowingValue(dummy_ * other.dummy_, no_throw_ctor);
   }
 
   ThrowingValue operator/(const ThrowingValue& other) const {
     exceptions_internal::MaybeThrow(ABSL_PRETTY_FUNCTION);
-    return ThrowingValue(dummy_ / other.dummy_, NoThrowTag{});
+    return ThrowingValue(dummy_ / other.dummy_, no_throw_ctor);
   }
 
   ThrowingValue operator%(const ThrowingValue& other) const {
     exceptions_internal::MaybeThrow(ABSL_PRETTY_FUNCTION);
-    return ThrowingValue(dummy_ % other.dummy_, NoThrowTag{});
+    return ThrowingValue(dummy_ % other.dummy_, no_throw_ctor);
   }
 
   ThrowingValue operator<<(int shift) const {
     exceptions_internal::MaybeThrow(ABSL_PRETTY_FUNCTION);
-    return ThrowingValue(dummy_ << shift, NoThrowTag{});
+    return ThrowingValue(dummy_ << shift, no_throw_ctor);
   }
 
   ThrowingValue operator>>(int shift) const {
     exceptions_internal::MaybeThrow(ABSL_PRETTY_FUNCTION);
-    return ThrowingValue(dummy_ >> shift, NoThrowTag{});
+    return ThrowingValue(dummy_ >> shift, no_throw_ctor);
   }
 
   // Comparison Operators
@@ -293,22 +338,22 @@ class ThrowingValue : private exceptions_internal::TrackedObject {
   // Bitwise Logical Operators
   ThrowingValue operator~() const {
     exceptions_internal::MaybeThrow(ABSL_PRETTY_FUNCTION);
-    return ThrowingValue(~dummy_, NoThrowTag{});
+    return ThrowingValue(~dummy_, no_throw_ctor);
   }
 
   ThrowingValue operator&(const ThrowingValue& other) const {
     exceptions_internal::MaybeThrow(ABSL_PRETTY_FUNCTION);
-    return ThrowingValue(dummy_ & other.dummy_, NoThrowTag{});
+    return ThrowingValue(dummy_ & other.dummy_, no_throw_ctor);
   }
 
   ThrowingValue operator|(const ThrowingValue& other) const {
     exceptions_internal::MaybeThrow(ABSL_PRETTY_FUNCTION);
-    return ThrowingValue(dummy_ | other.dummy_, NoThrowTag{});
+    return ThrowingValue(dummy_ | other.dummy_, no_throw_ctor);
   }
 
   ThrowingValue operator^(const ThrowingValue& other) const {
     exceptions_internal::MaybeThrow(ABSL_PRETTY_FUNCTION);
-    return ThrowingValue(dummy_ ^ other.dummy_, NoThrowTag{});
+    return ThrowingValue(dummy_ ^ other.dummy_, no_throw_ctor);
   }
 
   // Compound Assignment operators
@@ -434,10 +479,6 @@ class ThrowingValue : private exceptions_internal::TrackedObject {
   const int& Get() const noexcept { return dummy_; }
 
  private:
-  struct NoThrowTag {};
-  ThrowingValue(int i, NoThrowTag) noexcept
-      : TrackedObject(ABSL_PRETTY_FUNCTION), dummy_(i) {}
-
   int dummy_;
 };
 // While not having to do with exceptions, explicitly delete comma operator, to
@@ -596,7 +637,9 @@ int ThrowingAllocator<T, Throws>::next_id_ = 0;
 
 // Inspects the constructions and destructions of anything inheriting from
 // TrackedObject.  Place this as a member variable in a test fixture to ensure
-// that every ThrowingValue was constructed and destroyed correctly.
+// that every ThrowingValue was constructed and destroyed correctly.  This also
+// allows us to safely "leak" TrackedObjects, as AllocInspector will destroy
+// everything left over in its destructor.
 struct AllocInspector {
   AllocInspector() = default;
   ~AllocInspector() {
@@ -609,69 +652,79 @@ struct AllocInspector {
   }
 };
 
-// Tests that performing operation Op on a T follows the basic exception safety
-// guarantee.
+// Tests for resource leaks by attempting to construct a T using args repeatedly
+// until successful, using the countdown method.  Side effects can then be
+// tested for resource leaks.  If an AllocInspector is present in the test
+// fixture, then this will also test that memory resources are not leaked as
+// long as T allocates TrackedObjects.
+template <typename T, typename... Args>
+T TestThrowingCtor(Args&&... args) {
+  struct Cleanup {
+    ~Cleanup() { UnsetCountdown(); }
+  };
+  Cleanup c;
+  for (int countdown = 0;; ++countdown) {
+    exceptions_internal::countdown = countdown;
+    try {
+      return T(std::forward<Args>(args)...);
+    } catch (const exceptions_internal::TestException&) {
+    }
+  }
+}
+
+// Tests that performing operation Op on a T follows exception safety
+// guarantees.  By default only tests the basic guarantee.
 //
 // Parameters:
 //   * T: the type under test.
 //   * FunctionFromTPtrToVoid: A functor exercising the function under test.  It
-//     should take a T* and return void.
-//
-//  There must also be a function named `AbslCheckInvariants` in an associated
-//  namespace of T which takes a const T& and returns true if the T's class
-//  invariants hold, and false if they don't.
-template <typename T, typename FunctionFromTPtrToVoid>
-testing::AssertionResult TestBasicGuarantee(T* t, FunctionFromTPtrToVoid&& op) {
+//   should take a T* and return void.
+//   * Checkers: Any number of functions taking a const T& and returning
+//   anything contextually convertible to bool.  If a testing::AssertionResult
+//   is used then the error message is kept.  These test invariants related to
+//   the operation. To test the strong guarantee, pass
+//   absl::StrongGuarantee(...) as one of these arguments if T has operator==.
+//   Some types for which the strong guarantee makes sense don't have operator==
+//   (eg std::any).  A function capturing *t or a T equal to it, taking a const
+//   T&, and returning contextually-convertible-to-bool may be passed instead.
+template <typename T, typename FunctionFromTPtrToVoid, typename... Checkers>
+testing::AssertionResult TestExceptionSafety(T* t, FunctionFromTPtrToVoid&& op,
+                                             const Checkers&... checkers) {
+  auto out = testing::AssertionSuccess();
   for (int countdown = 0;; ++countdown) {
     exceptions_internal::countdown = countdown;
     try {
       op(t);
       break;
     } catch (const exceptions_internal::TestException& e) {
-      if (!AbslCheckInvariants(*t)) {
-        return exceptions_internal::FailureMessage(e, countdown)
-               << " broke invariants.";
-      }
+      out = exceptions_internal::TestInvariants(*t, e, countdown, checkers...);
+      if (!out) return out;
     }
   }
-  exceptions_internal::countdown = -1;
-  return testing::AssertionSuccess();
+  UnsetCountdown();
+  return out;
 }
 
-// Tests that performing operation Op on a T follows the strong exception safety
-// guarantee.
+// Returns a functor to test for the strong exception-safety guarantee.  If T is
+// copyable, use the const T& overload, otherwise pass a unique_ptr<T>.
+// Equality comparisons are made against the T provided and default to using
+// operator==.  See the documentation for TestExceptionSafety if T doesn't have
+// operator== but the strong guarantee still makes sense for it.
 //
 // Parameters:
-//   * T: the type under test. T must be copy-constructable and
-//   equality-comparible.
-//   * FunctionFromTPtrToVoid: A functor exercising the function under test.  It
-//     should take a T* and return void.
-//
-//  There must also be a function named `AbslCheckInvariants` in an associated
-//  namespace of T which takes a const T& and returns true if the T's class
-//  invariants hold, and false if they don't.
-template <typename T, typename FunctionFromTPtrToVoid>
-testing::AssertionResult TestStrongGuarantee(T* t,
-                                             FunctionFromTPtrToVoid&& op) {
-  exceptions_internal::countdown = -1;
-  for (auto countdown = 0;; ++countdown) {
-    T dup = *t;
-    exceptions_internal::countdown = countdown;
-    try {
-      op(t);
-      break;
-    } catch (const exceptions_internal::TestException& e) {
-      if (!AbslCheckInvariants(*t)) {
-        return exceptions_internal::FailureMessage(e, countdown)
-               << " broke invariants.";
-      }
-      if (dup != *t)
-        return exceptions_internal::FailureMessage(e, countdown)
-               << " changed state.";
-    }
-  }
-  exceptions_internal::countdown = -1;
-  return testing::AssertionSuccess();
+//   * T: The type under test.
+template <typename T, typename EqualTo = std::equal_to<T>>
+exceptions_internal::StrongGuaranteeTester<T, EqualTo> StrongGuarantee(
+    const T& t, EqualTo eq = EqualTo()) {
+  return exceptions_internal::StrongGuaranteeTester<T, EqualTo>(
+      absl::make_unique<T>(t), eq);
+}
+
+template <typename T, typename EqualTo = std::equal_to<T>>
+exceptions_internal::StrongGuaranteeTester<T, EqualTo> PointeeStrongGuarantee(
+    std::unique_ptr<T> t_ptr, EqualTo eq = EqualTo()) {
+  return exceptions_internal::StrongGuaranteeTester<T, EqualTo>(
+      std::move(t_ptr), eq);
 }
 
 }  // namespace absl
diff --git a/absl/strings/strip_test.cc b/absl/strings/strip_test.cc
index 3c9e726ee..ff0e7f1c2 100644
--- a/absl/strings/strip_test.cc
+++ b/absl/strings/strip_test.cc
@@ -116,4 +116,66 @@ TEST(Strip, StripSuffix) {
   EXPECT_EQ(absl::StripSuffix("", ""), "");
 }
 
+TEST(Strip, RemoveExtraAsciiWhitespace) {
+  const char* inputs[] = {
+      "No extra space",
+      "  Leading whitespace",
+      "Trailing whitespace  ",
+      "  Leading and trailing  ",
+      " Whitespace \t  in\v   middle  ",
+      "'Eeeeep!  \n Newlines!\n",
+      "nospaces",
+  };
+  const char* outputs[] = {
+      "No extra space",
+      "Leading whitespace",
+      "Trailing whitespace",
+      "Leading and trailing",
+      "Whitespace in middle",
+      "'Eeeeep! Newlines!",
+      "nospaces",
+  };
+  int NUM_TESTS = 7;
+
+  for (int i = 0; i < NUM_TESTS; i++) {
+    std::string s(inputs[i]);
+    absl::RemoveExtraAsciiWhitespace(&s);
+    EXPECT_STREQ(outputs[i], s.c_str());
+  }
+
+  // Test that absl::RemoveExtraAsciiWhitespace returns immediately for empty
+  // strings (It was adding the \0 character to the C++ std::string, which broke
+  // tests involving empty())
+  std::string zero_string = "";
+  assert(zero_string.empty());
+  absl::RemoveExtraAsciiWhitespace(&zero_string);
+  EXPECT_EQ(zero_string.size(), 0);
+  EXPECT_TRUE(zero_string.empty());
+}
+
+TEST(Strip, StripTrailingAsciiWhitespace) {
+  std::string test = "foo  ";
+  absl::StripTrailingAsciiWhitespace(&test);
+  EXPECT_EQ(test, "foo");
+
+  test = "   ";
+  absl::StripTrailingAsciiWhitespace(&test);
+  EXPECT_EQ(test, "");
+
+  test = "";
+  absl::StripTrailingAsciiWhitespace(&test);
+  EXPECT_EQ(test, "");
+
+  test = " abc\t";
+  absl::StripTrailingAsciiWhitespace(&test);
+  EXPECT_EQ(test, " abc");
+}
+
+TEST(String, StripLeadingAsciiWhitespace) {
+  absl::string_view orig = "\t  \n\f\r\n\vfoo";
+  EXPECT_EQ("foo", absl::StripLeadingAsciiWhitespace(orig));
+  orig = "\t  \n\f\r\v\n\t  \n\f\r\v\n";
+  EXPECT_EQ(absl::string_view(), absl::StripLeadingAsciiWhitespace(orig));
+}
+
 }  // namespace
diff --git a/absl/time/duration.cc b/absl/time/duration.cc
index f5081955d..5e4f93136 100644
--- a/absl/time/duration.cc
+++ b/absl/time/duration.cc
@@ -672,7 +672,7 @@ namespace {
 char* Format64(char* ep, int width, int64_t v) {
   do {
     --width;
-    *--ep = "0123456789"[v % 10];
+    *--ep = '0' + (v % 10);  // contiguous digits
   } while (v /= 10);
   while (--width >= 0) *--ep = '0';  // zero pad
   return ep;
@@ -782,15 +782,32 @@ std::string FormatDuration(Duration d) {
 namespace {
 
 // A helper for ParseDuration() that parses a leading number from the given
-// std::string and stores the result in *n.  The given std::string pointer is modified
-// to point to the first unconsumed char.
-bool ConsumeDurationNumber(const char** start, double* n) {
-  const char* s = *start;
-  char* end = nullptr;
-  errno = 0;
-  *n = strtod(s, &end);
-  *start = end;
-  return !std::isspace(*s) && errno == 0 && end != s && *n >= 0;
+// std::string and stores the result in *int_part/*frac_part/*frac_scale.  The
+// given std::string pointer is modified to point to the first unconsumed char.
+bool ConsumeDurationNumber(const char** dpp, int64_t* int_part,
+                           int64_t* frac_part, int64_t* frac_scale) {
+  *int_part = 0;
+  *frac_part = 0;
+  *frac_scale = 1;  // invariant: *frac_part < *frac_scale
+  const char* start = *dpp;
+  for (; std::isdigit(**dpp); *dpp += 1) {
+    const int d = **dpp - '0';  // contiguous digits
+    if (*int_part > kint64max / 10) return false;
+    *int_part *= 10;
+    if (*int_part > kint64max - d) return false;
+    *int_part += d;
+  }
+  const bool int_part_empty = (*dpp == start);
+  if (**dpp != '.') return !int_part_empty;
+  for (*dpp += 1; std::isdigit(**dpp); *dpp += 1) {
+    const int d = **dpp - '0';  // contiguous digits
+    if (*frac_scale <= kint64max / 10) {
+      *frac_part *= 10;
+      *frac_part += d;
+      *frac_scale *= 10;
+    }
+  }
+  return !int_part_empty || *frac_scale != 1;
 }
 
 // A helper for ParseDuration() that parses a leading unit designator (e.g.,
@@ -859,13 +876,16 @@ bool ParseDuration(const std::string& dur_string, Duration* d) {
 
   Duration dur;
   while (*start != '\0') {
-    double n = 0;
+    int64_t int_part;
+    int64_t frac_part;
+    int64_t frac_scale;
     Duration unit;
-    if (!ConsumeDurationNumber(&start, &n) ||
+    if (!ConsumeDurationNumber(&start, &int_part, &frac_part, &frac_scale) ||
         !ConsumeDurationUnit(&start, &unit)) {
       return false;
     }
-    dur += sign * n * unit;
+    if (int_part != 0) dur += sign * int_part * unit;
+    if (frac_part != 0) dur += sign * frac_part * unit / frac_scale;
   }
   *d = dur;
   return true;
diff --git a/absl/time/duration_test.cc b/absl/time/duration_test.cc
index 7f4522874..7918e1677 100644
--- a/absl/time/duration_test.cc
+++ b/absl/time/duration_test.cc
@@ -1573,6 +1573,7 @@ TEST(Duration, ParseDuration) {
   EXPECT_FALSE(absl::ParseDuration("2s ", &d));
   EXPECT_FALSE(absl::ParseDuration(" 2s ", &d));
   EXPECT_FALSE(absl::ParseDuration("2mt", &d));
+  EXPECT_FALSE(absl::ParseDuration("1e3s", &d));
 
   // One unit type.
   EXPECT_TRUE(absl::ParseDuration("1ns", &d));
@@ -1588,6 +1589,12 @@ TEST(Duration, ParseDuration) {
   EXPECT_TRUE(absl::ParseDuration("2h", &d));
   EXPECT_EQ(absl::Hours(2), d);
 
+  // Huge counts of a unit.
+  EXPECT_TRUE(absl::ParseDuration("9223372036854775807us", &d));
+  EXPECT_EQ(absl::Microseconds(9223372036854775807), d);
+  EXPECT_TRUE(absl::ParseDuration("-9223372036854775807us", &d));
+  EXPECT_EQ(absl::Microseconds(-9223372036854775807), d);
+
   // Multiple units.
   EXPECT_TRUE(absl::ParseDuration("2h3m4s", &d));
   EXPECT_EQ(absl::Hours(2) + absl::Minutes(3) + absl::Seconds(4), d);
@@ -1619,6 +1626,12 @@ TEST(Duration, ParseDuration) {
   EXPECT_TRUE(absl::ParseDuration("1.5h", &d));
   EXPECT_EQ(1.5 * absl::Hours(1), d);
 
+  // Huge fractional counts of a unit.
+  EXPECT_TRUE(absl::ParseDuration("0.4294967295s", &d));
+  EXPECT_EQ(absl::Nanoseconds(429496729) + absl::Nanoseconds(1) / 2, d);
+  EXPECT_TRUE(absl::ParseDuration("0.429496729501234567890123456789s", &d));
+  EXPECT_EQ(absl::Nanoseconds(429496729) + absl::Nanoseconds(1) / 2, d);
+
   // Negative durations.
   EXPECT_TRUE(absl::ParseDuration("-1s", &d));
   EXPECT_EQ(absl::Seconds(-1), d);