23 files changed, 168 insertions, 31 deletions
diff --git a/absl/algorithm/BUILD.bazel b/absl/algorithm/BUILD.bazel
index 229cd713..a3002b7d 100644
--- a/absl/algorithm/BUILD.bazel
+++ b/absl/algorithm/BUILD.bazel
@@ -24,7 +24,7 @@ load(
 
 package(default_visibility = ["//visibility:public"])
 
-licenses(["notice"])  # Apache 2.0
+licenses(["notice"])
 
 cc_library(
     name = "algorithm",
diff --git a/absl/base/BUILD.bazel b/absl/base/BUILD.bazel
index 2c4887b3..9d96abeb 100644
--- a/absl/base/BUILD.bazel
+++ b/absl/base/BUILD.bazel
@@ -24,7 +24,7 @@ load(
 
 package(default_visibility = ["//visibility:public"])
 
-licenses(["notice"])  # Apache 2.0
+licenses(["notice"])
 
 cc_library(
     name = "atomic_hook",
diff --git a/absl/container/BUILD.bazel b/absl/container/BUILD.bazel
index cca5d441..8e72ad03 100644
--- a/absl/container/BUILD.bazel
+++ b/absl/container/BUILD.bazel
@@ -24,7 +24,7 @@ load(
 
 package(default_visibility = ["//visibility:public"])
 
-licenses(["notice"])  # Apache 2.0
+licenses(["notice"])
 
 cc_library(
     name = "compressed_tuple",
diff --git a/absl/container/internal/container_memory.h b/absl/container/internal/container_memory.h
index d02c576d..e67529ec 100644
--- a/absl/container/internal/container_memory.h
+++ b/absl/container/internal/container_memory.h
@@ -57,8 +57,11 @@ void* Allocate(Alloc* alloc, size_t n) {
   using M = AlignedType<Alignment>;
   using A = typename absl::allocator_traits<Alloc>::template rebind_alloc<M>;
   using AT = typename absl::allocator_traits<Alloc>::template rebind_traits<M>;
-  A mem_alloc(*alloc);
-  void* p = AT::allocate(mem_alloc, (n + sizeof(M) - 1) / sizeof(M));
+  // On macOS, "mem_alloc" is a #define with one argument defined in
+  // rpc/types.h, so we can't name the variable "mem_alloc" and initialize it
+  // with the "foo(bar)" syntax.
+  A my_mem_alloc(*alloc);
+  void* p = AT::allocate(my_mem_alloc, (n + sizeof(M) - 1) / sizeof(M));
   assert(reinterpret_cast<uintptr_t>(p) % Alignment == 0 &&
          "allocator does not respect alignment");
   return p;
@@ -73,8 +76,11 @@ void Deallocate(Alloc* alloc, void* p, size_t n) {
   using M = AlignedType<Alignment>;
   using A = typename absl::allocator_traits<Alloc>::template rebind_alloc<M>;
   using AT = typename absl::allocator_traits<Alloc>::template rebind_traits<M>;
-  A mem_alloc(*alloc);
-  AT::deallocate(mem_alloc, static_cast<M*>(p),
+  // On macOS, "mem_alloc" is a #define with one argument defined in
+  // rpc/types.h, so we can't name the variable "mem_alloc" and initialize it
+  // with the "foo(bar)" syntax.
+  A my_mem_alloc(*alloc);
+  AT::deallocate(my_mem_alloc, static_cast<M*>(p),
                  (n + sizeof(M) - 1) / sizeof(M));
 }
 
diff --git a/absl/container/internal/raw_hash_set.h b/absl/container/internal/raw_hash_set.h
index 48a1a8c6..130da13c 100644
--- a/absl/container/internal/raw_hash_set.h
+++ b/absl/container/internal/raw_hash_set.h
@@ -122,6 +122,16 @@ namespace absl {
 ABSL_NAMESPACE_BEGIN
 namespace container_internal {
 
+template <typename AllocType>
+void SwapAlloc(AllocType& lhs, AllocType& rhs,
+               std::true_type /* propagate_on_container_swap */) {
+  using std::swap;
+  swap(lhs, rhs);
+}
+template <typename AllocType>
+void SwapAlloc(AllocType& /*lhs*/, AllocType& /*rhs*/,
+               std::false_type /* propagate_on_container_swap */) {}
+
 template <size_t Width>
 class probe_seq {
  public:
@@ -169,10 +179,14 @@ struct IsDecomposable<
 
 // TODO(alkis): Switch to std::is_nothrow_swappable when gcc/clang supports it.
 template <class T>
-constexpr bool IsNoThrowSwappable() {
+constexpr bool IsNoThrowSwappable(std::true_type = {} /* is_swappable */) {
   using std::swap;
   return noexcept(swap(std::declval<T&>(), std::declval<T&>()));
 }
+template <class T>
+constexpr bool IsNoThrowSwappable(std::false_type /* is_swappable */) {
+  return false;
+}
 
 template <typename T>
 int TrailingZeros(T x) {
@@ -1231,8 +1245,8 @@ class raw_hash_set {
 
   void swap(raw_hash_set& that) noexcept(
       IsNoThrowSwappable<hasher>() && IsNoThrowSwappable<key_equal>() &&
-      (!AllocTraits::propagate_on_container_swap::value ||
-       IsNoThrowSwappable<allocator_type>())) {
+      IsNoThrowSwappable<allocator_type>(
+          typename AllocTraits::propagate_on_container_swap{})) {
     using std::swap;
     swap(ctrl_, that.ctrl_);
     swap(slots_, that.slots_);
@@ -1242,12 +1256,8 @@ class raw_hash_set {
     swap(hash_ref(), that.hash_ref());
     swap(eq_ref(), that.eq_ref());
     swap(infoz_, that.infoz_);
-    if (AllocTraits::propagate_on_container_swap::value) {
-      swap(alloc_ref(), that.alloc_ref());
-    } else {
-      // If the allocators do not compare equal it is officially undefined
-      // behavior. We choose to do nothing.
-    }
+    SwapAlloc(alloc_ref(), that.alloc_ref(),
+              typename AllocTraits::propagate_on_container_swap{});
   }
 
   void rehash(size_t n) {
diff --git a/absl/container/internal/raw_hash_set_allocator_test.cc b/absl/container/internal/raw_hash_set_allocator_test.cc
index 7ac4b9f7..1a036085 100644
--- a/absl/container/internal/raw_hash_set_allocator_test.cc
+++ b/absl/container/internal/raw_hash_set_allocator_test.cc
@@ -424,6 +424,77 @@ TEST_F(PropagateOnAll, Swap) {
   EXPECT_EQ(0, it->num_copies());
 }
 
+// This allocator is similar to std::pmr::polymorphic_allocator.
+// Note the disabled assignment.
+template <class T>
+class PAlloc {
+  template <class>
+  friend class PAlloc;
+
+ public:
+  // types
+  using value_type = T;
+
+  // traits
+  using propagate_on_container_swap = std::false_type;
+
+  PAlloc() noexcept = default;
+  explicit PAlloc(size_t id) noexcept : id_(id) {}
+  PAlloc(const PAlloc&) noexcept = default;
+  PAlloc& operator=(const PAlloc&) noexcept = delete;
+
+  template <class U>
+  PAlloc(const PAlloc<U>& that) noexcept : id_(that.id_) {}  // NOLINT
+
+  template <class U>
+  struct rebind {
+    using other = PAlloc<U>;
+  };
+
+  constexpr PAlloc select_on_container_copy_construction() const { return {}; }
+
+  // public member functions
+  T* allocate(size_t) { return new T; }
+  void deallocate(T* p, size_t) { delete p; }
+
+  friend bool operator==(const PAlloc& a, const PAlloc& b) {
+    return a.id_ == b.id_;
+  }
+  friend bool operator!=(const PAlloc& a, const PAlloc& b) { return !(a == b); }
+
+ private:
+  size_t id_ = std::numeric_limits<size_t>::max();
+};
+
+TEST(NoPropagateOn, Swap) {
+  using PA = PAlloc<char>;
+  using Table = raw_hash_set<Policy, Identity, std::equal_to<int32_t>, PA>;
+
+  Table t1(PA{1}), t2(PA{2});
+  swap(t1, t2);
+  EXPECT_EQ(t1.get_allocator(), PA(1));
+  EXPECT_EQ(t2.get_allocator(), PA(2));
+}
+
+TEST(NoPropagateOn, CopyConstruct) {
+  using PA = PAlloc<char>;
+  using Table = raw_hash_set<Policy, Identity, std::equal_to<int32_t>, PA>;
+
+  Table t1(PA{1}), t2(t1);
+  EXPECT_EQ(t1.get_allocator(), PA(1));
+  EXPECT_EQ(t2.get_allocator(), PA());
+}
+
+TEST(NoPropagateOn, Assignment) {
+  using PA = PAlloc<char>;
+  using Table = raw_hash_set<Policy, Identity, std::equal_to<int32_t>, PA>;
+
+  Table t1(PA{1}), t2(PA{2});
+  t1 = t2;
+  EXPECT_EQ(t1.get_allocator(), PA(1));
+  EXPECT_EQ(t2.get_allocator(), PA(2));
+}
+
 }  // namespace
 }  // namespace container_internal
 ABSL_NAMESPACE_END
diff --git a/absl/debugging/BUILD.bazel b/absl/debugging/BUILD.bazel
index 9098ca4a..86faac9b 100644
--- a/absl/debugging/BUILD.bazel
+++ b/absl/debugging/BUILD.bazel
@@ -26,7 +26,7 @@ package(
     default_visibility = ["//visibility:public"],
 )
 
-licenses(["notice"])  # Apache 2.0
+licenses(["notice"])
 
 cc_library(
     name = "stacktrace",
diff --git a/absl/flags/BUILD.bazel b/absl/flags/BUILD.bazel
index 92bd4f15..62fb9a8b 100644
--- a/absl/flags/BUILD.bazel
+++ b/absl/flags/BUILD.bazel
@@ -24,7 +24,7 @@ load(
 
 package(default_visibility = ["//visibility:public"])
 
-licenses(["notice"])  # Apache 2.0
+licenses(["notice"])
 
 cc_library(
     name = "path_util",
@@ -179,6 +179,7 @@ cc_library(
         ":private_handle_accessor",
         "//absl/base:config",
         "//absl/base:core_headers",
+        "//absl/container:flat_hash_map",
         "//absl/strings",
         "//absl/synchronization",
     ],
@@ -464,6 +465,7 @@ cc_test(
         ":flag",
         ":marshalling",
         ":reflection",
+        ":usage_internal",
         "//absl/memory",
         "//absl/strings",
         "@com_google_googletest//:gtest_main",
diff --git a/absl/flags/CMakeLists.txt b/absl/flags/CMakeLists.txt
index 343774de..28bd5a85 100644
--- a/absl/flags/CMakeLists.txt
+++ b/absl/flags/CMakeLists.txt
@@ -165,6 +165,7 @@ absl_cc_library(
     absl::flags_config
     absl::strings
     absl::synchronization
+    absl::flat_hash_map
 )
 
 # Internal-only target, do not depend on directly.
@@ -407,9 +408,10 @@ absl_cc_test(
     absl::flags_commandlineflag_internal
     absl::flags
     absl::flags_reflection
+    absl::flags_usage
     absl::memory
     absl::strings
-    gtest_main
+    gmock_main
 )
 
 absl_cc_test(
diff --git a/absl/flags/reflection.cc b/absl/flags/reflection.cc
index e4145b34..d7060221 100644
--- a/absl/flags/reflection.cc
+++ b/absl/flags/reflection.cc
@@ -303,5 +303,15 @@ CommandLineFlag* FindCommandLineFlag(absl::string_view name) {
   return registry.FindFlagLocked(name);
 }
 
+// --------------------------------------------------------------------
+
+absl::flat_hash_map<absl::string_view, absl::CommandLineFlag*> GetAllFlags() {
+  absl::flat_hash_map<absl::string_view, absl::CommandLineFlag*> res;
+  flags_internal::ForEachFlag([&](CommandLineFlag& flag) {
+    res.insert({flag.Name(), &flag});
+  });
+  return res;
+}
+
 ABSL_NAMESPACE_END
 }  // namespace absl
diff --git a/absl/flags/reflection.h b/absl/flags/reflection.h
index 045f9784..4ce0ab6c 100644
--- a/absl/flags/reflection.h
+++ b/absl/flags/reflection.h
@@ -26,6 +26,7 @@
 #include <string>
 
 #include "absl/base/config.h"
+#include "absl/container/flat_hash_map.h"
 #include "absl/flags/commandlineflag.h"
 #include "absl/flags/internal/commandlineflag.h"
 
@@ -40,7 +41,11 @@ class FlagSaverImpl;
 // Returns the reflection handle of an Abseil flag of the specified name, or
 // `nullptr` if not found. This function will emit a warning if the name of a
 // 'retired' flag is specified.
-CommandLineFlag* FindCommandLineFlag(absl::string_view name);
+absl::CommandLineFlag* FindCommandLineFlag(absl::string_view name);
+
+// Returns current state of the Flags registry in a form of mapping from flag
+// name to a flag reflection handle.
+absl::flat_hash_map<absl::string_view, absl::CommandLineFlag*> GetAllFlags();
 
 //------------------------------------------------------------------------------
 // FlagSaver
diff --git a/absl/flags/reflection_test.cc b/absl/flags/reflection_test.cc
index 2da0a0ec..1a1dcb4a 100644
--- a/absl/flags/reflection_test.cc
+++ b/absl/flags/reflection_test.cc
@@ -18,7 +18,9 @@
 #include <memory>
 #include <string>
 
+#include "gmock/gmock.h"
 #include "gtest/gtest.h"
+#include "absl/flags/declare.h"
 #include "absl/flags/flag.h"
 #include "absl/flags/internal/commandlineflag.h"
 #include "absl/flags/marshalling.h"
@@ -30,6 +32,8 @@ ABSL_FLAG(int, int_flag, 1, "int_flag help");
 ABSL_FLAG(std::string, string_flag, "dflt", "string_flag help");
 ABSL_RETIRED_FLAG(bool, bool_retired_flag, false, "bool_retired_flag help");
 
+ABSL_DECLARE_FLAG(bool, help);
+
 namespace {
 
 namespace flags = absl::flags_internal;
@@ -61,6 +65,33 @@ TEST_F(ReflectionTest, TestFindCommandLineFlag) {
 
 // --------------------------------------------------------------------
 
+TEST_F(ReflectionTest, TestGetAllFlags) {
+  (void)absl::GetFlag(FLAGS_help);  // Force linking of usage flags.
+
+  auto all_flags = absl::GetAllFlags();
+  EXPECT_NE(all_flags.find("int_flag"), all_flags.end());
+  EXPECT_NE(all_flags.find("bool_retired_flag"), all_flags.end());
+  EXPECT_NE(all_flags.find("help"), all_flags.end());
+  EXPECT_EQ(all_flags.find("some_undefined_flag"), all_flags.end());
+
+  std::vector<absl::string_view> flag_names_first_attempt;
+  auto all_flags_1 = absl::GetAllFlags();
+  for (auto f : all_flags_1) {
+    flag_names_first_attempt.push_back(f.first);
+  }
+
+  std::vector<absl::string_view> flag_names_second_attempt;
+  auto all_flags_2 = absl::GetAllFlags();
+  for (auto f : all_flags_2) {
+    flag_names_second_attempt.push_back(f.first);
+  }
+
+  EXPECT_THAT(flag_names_first_attempt,
+              ::testing::UnorderedElementsAreArray(flag_names_second_attempt));
+}
+
+// --------------------------------------------------------------------
+
 struct CustomUDT {
   CustomUDT() : a(1), b(1) {}
   CustomUDT(int a_, int b_) : a(a_), b(b_) {}
diff --git a/absl/functional/BUILD.bazel b/absl/functional/BUILD.bazel
index 432546ce..ebd9b99b 100644
--- a/absl/functional/BUILD.bazel
+++ b/absl/functional/BUILD.bazel
@@ -24,7 +24,7 @@ load(
 
 package(default_visibility = ["//visibility:public"])
 
-licenses(["notice"])  # Apache 2.0
+licenses(["notice"])
 
 cc_library(
     name = "bind_front",
diff --git a/absl/hash/BUILD.bazel b/absl/hash/BUILD.bazel
index 6c77f1a1..5b1e2d01 100644
--- a/absl/hash/BUILD.bazel
+++ b/absl/hash/BUILD.bazel
@@ -24,7 +24,7 @@ load(
 
 package(default_visibility = ["//visibility:public"])
 
-licenses(["notice"])  # Apache 2.0
+licenses(["notice"])
 
 cc_library(
     name = "hash",
diff --git a/absl/memory/BUILD.bazel b/absl/memory/BUILD.bazel
index 2ba9d7cb..d2824a05 100644
--- a/absl/memory/BUILD.bazel
+++ b/absl/memory/BUILD.bazel
@@ -24,7 +24,7 @@ load(
 
 package(default_visibility = ["//visibility:public"])
 
-licenses(["notice"])  # Apache 2.0
+licenses(["notice"])
 
 cc_library(
     name = "memory",
diff --git a/absl/meta/BUILD.bazel b/absl/meta/BUILD.bazel
index c06d2d97..5585fcca 100644
--- a/absl/meta/BUILD.bazel
+++ b/absl/meta/BUILD.bazel
@@ -24,7 +24,7 @@ load(
 
 package(default_visibility = ["//visibility:public"])
 
-licenses(["notice"])  # Apache 2.0
+licenses(["notice"])
 
 cc_library(
     name = "type_traits",
diff --git a/absl/numeric/BUILD.bazel b/absl/numeric/BUILD.bazel
index da3af4d0..f808f5da 100644
--- a/absl/numeric/BUILD.bazel
+++ b/absl/numeric/BUILD.bazel
@@ -22,7 +22,7 @@ load(
 
 package(default_visibility = ["//visibility:public"])
 
-licenses(["notice"])  # Apache 2.0
+licenses(["notice"])
 
 cc_library(
     name = "int128",
diff --git a/absl/random/internal/BUILD.bazel b/absl/random/internal/BUILD.bazel
index 000cc45b..8485e28b 100644
--- a/absl/random/internal/BUILD.bazel
+++ b/absl/random/internal/BUILD.bazel
@@ -30,7 +30,7 @@ package(default_visibility = [
     "//absl/random:__pkg__",
 ])
 
-licenses(["notice"])  # Apache 2.0
+licenses(["notice"])
 
 cc_library(
     name = "traits",
diff --git a/absl/status/BUILD.bazel b/absl/status/BUILD.bazel
index c4c5e497..81fa46c2 100644
--- a/absl/status/BUILD.bazel
+++ b/absl/status/BUILD.bazel
@@ -26,7 +26,7 @@ load(
 
 package(default_visibility = ["//visibility:public"])
 
-licenses(["notice"])  # Apache 2.0
+licenses(["notice"])
 
 cc_library(
     name = "status",
diff --git a/absl/synchronization/BUILD.bazel b/absl/synchronization/BUILD.bazel
index 1a5c02ab..4d4d6806 100644
--- a/absl/synchronization/BUILD.bazel
+++ b/absl/synchronization/BUILD.bazel
@@ -24,7 +24,7 @@ load(
 
 package(default_visibility = ["//visibility:public"])
 
-licenses(["notice"])  # Apache 2.0
+licenses(["notice"])
 
 # Internal data structure for efficiently detecting mutex dependency cycles
 cc_library(
diff --git a/absl/time/BUILD.bazel b/absl/time/BUILD.bazel
index 1d69f598..991241a0 100644
--- a/absl/time/BUILD.bazel
+++ b/absl/time/BUILD.bazel
@@ -24,7 +24,7 @@ load(
 
 package(default_visibility = ["//visibility:public"])
 
-licenses(["notice"])  # Apache 2.0
+licenses(["notice"])
 
 cc_library(
     name = "time",
diff --git a/absl/types/BUILD.bazel b/absl/types/BUILD.bazel
index 102affaf..83be9360 100644
--- a/absl/types/BUILD.bazel
+++ b/absl/types/BUILD.bazel
@@ -23,7 +23,7 @@ load(
 
 package(default_visibility = ["//visibility:public"])
 
-licenses(["notice"])  # Apache 2.0
+licenses(["notice"])
 
 cc_library(
     name = "any",
diff --git a/absl/utility/BUILD.bazel b/absl/utility/BUILD.bazel
index 6881f939..02b2c407 100644
--- a/absl/utility/BUILD.bazel
+++ b/absl/utility/BUILD.bazel
@@ -24,7 +24,7 @@ load(
 
 package(default_visibility = ["//visibility:public"])
 
-licenses(["notice"])  # Apache 2.0
+licenses(["notice"])
 
 cc_library(
     name = "utility",