Export of internal Abseil changes

--
30e5e00a54cabc50118a3e1055826ea02a0d32e4 by Gennadiy Rozental <rogeeff@google.com>:

Move flag help into flag_cold section.

To facilitate this we set flag help not in a constructor, but during flag registration. This allows us to place flag name as static variable inside non constexpr lambda and invoke it immediately in FlagRegistrar argument location.

PiperOrigin-RevId: 312432625

--
efd91b05152b68df648cff5ba38e9669a817c12f by Gennadiy Rozental <rogeeff@google.com>:

Make CommandLineFlag public.

PiperOrigin-RevId: 312404666

--
dc7f5fb73487766fa8a76d6b97d28116e5334445 by Mark Barolak <mbar@google.com>:

Internal change.

PiperOrigin-RevId: 312297164
GitOrigin-RevId: 30e5e00a54cabc50118a3e1055826ea02a0d32e4
Change-Id: Ic46ab011bb804645264572caddff0becba5f9170

20 files changed, 420 insertions, 325 deletions

diff --git a/absl/flags/BUILD.bazel b/absl/flags/BUILD.bazel
index 36810825..2d6f799e 100644
--- a/absl/flags/BUILD.bazel
+++ b/absl/flags/BUILD.bazel
@@ -27,28 +27,18 @@ package(default_visibility = ["//visibility:public"])
 licenses(["notice"])  # Apache 2.0
 
 cc_library(
-    name = "flag_internal",
-    srcs = [
-        "internal/flag.cc",
-    ],
+    name = "path_util",
     hdrs = [
-        "internal/flag.h",
+        "internal/path_util.h",
     ],
     copts = ABSL_DEFAULT_COPTS,
     linkopts = ABSL_DEFAULT_LINKOPTS,
-    visibility = ["//absl/base:__subpackages__"],
+    visibility = [
+        "//absl/flags:__pkg__",
+    ],
     deps = [
-        ":config",
-        ":handle",
-        ":marshalling",
-        ":registry",
-        "//absl/base",
         "//absl/base:config",
-        "//absl/base:core_headers",
-        "//absl/memory",
-        "//absl/meta:type_traits",
         "//absl/strings",
-        "//absl/synchronization",
     ],
 )
 
@@ -75,22 +65,6 @@ cc_library(
 )
 
 cc_library(
-    name = "path_util",
-    hdrs = [
-        "internal/path_util.h",
-    ],
-    copts = ABSL_DEFAULT_COPTS,
-    linkopts = ABSL_DEFAULT_LINKOPTS,
-    visibility = [
-        "//absl/flags:__pkg__",
-    ],
-    deps = [
-        "//absl/base:config",
-        "//absl/strings",
-    ],
-)
-
-cc_library(
     name = "config",
     srcs = [
         "usage_config.cc",
@@ -131,23 +105,33 @@ cc_library(
 )
 
 cc_library(
-    name = "handle",
-    srcs = [
-        "internal/commandlineflag.cc",
-    ],
+    name = "commandlineflag_internal",
     hdrs = [
         "internal/commandlineflag.h",
     ],
     copts = ABSL_DEFAULT_COPTS,
     linkopts = ABSL_DEFAULT_LINKOPTS,
-    visibility = [
-        "//absl/flags:__pkg__",
-    ],
+    visibility = ["//visibility:private"],
     deps = [
         "//absl/base:config",
         "//absl/base:core_headers",
         "//absl/base:fast_type_id",
         "//absl/strings",
+    ],
+)
+
+cc_library(
+    name = "commandlineflag",
+    srcs = [
+        "commandlineflag.cc",
+    ],
+    hdrs = [
+        "commandlineflag.h",
+    ],
+    copts = ABSL_DEFAULT_COPTS,
+    linkopts = ABSL_DEFAULT_LINKOPTS,
+    deps = [
+        ":commandlineflag_internal",
         "//absl/types:optional",
     ],
 )
@@ -165,7 +149,7 @@ cc_library(
     visibility = [
         "//absl/flags:__pkg__",
     ],
-    deps = [":handle"],
+    deps = [":commandlineflag"],
 )
 
 cc_library(
@@ -184,8 +168,9 @@ cc_library(
         "//absl/flags:__pkg__",
     ],
     deps = [
+        ":commandlineflag",
+        ":commandlineflag_internal",
         ":config",
-        ":handle",
         ":private_handle_accessor",
         "//absl/base:config",
         "//absl/base:core_headers",
@@ -196,6 +181,32 @@ cc_library(
 )
 
 cc_library(
+    name = "flag_internal",
+    srcs = [
+        "internal/flag.cc",
+    ],
+    hdrs = [
+        "internal/flag.h",
+    ],
+    copts = ABSL_DEFAULT_COPTS,
+    linkopts = ABSL_DEFAULT_LINKOPTS,
+    visibility = ["//absl/base:__subpackages__"],
+    deps = [
+        ":commandlineflag",
+        ":config",
+        ":marshalling",
+        ":registry",
+        "//absl/base",
+        "//absl/base:config",
+        "//absl/base:core_headers",
+        "//absl/memory",
+        "//absl/meta:type_traits",
+        "//absl/strings",
+        "//absl/synchronization",
+    ],
+)
+
+cc_library(
     name = "flag",
     srcs = [
         "flag.cc",
@@ -209,7 +220,6 @@ cc_library(
     deps = [
         ":config",
         ":flag_internal",
-        ":handle",
         ":marshalling",
         ":registry",
         "//absl/base",
@@ -233,10 +243,10 @@ cc_library(
         "//absl/flags:__pkg__",
     ],
     deps = [
+        ":commandlineflag",
         ":config",
         ":flag",
         ":flag_internal",
-        ":handle",
         ":path_util",
         ":private_handle_accessor",
         ":program_name",
@@ -276,10 +286,10 @@ cc_library(
     copts = ABSL_DEFAULT_COPTS,
     linkopts = ABSL_DEFAULT_LINKOPTS,
     deps = [
+        ":commandlineflag",
         ":config",
         ":flag",
         ":flag_internal",
-        ":handle",
         ":private_handle_accessor",
         ":program_name",
         ":registry",
@@ -299,14 +309,14 @@ cc_test(
     name = "commandlineflag_test",
     size = "small",
     srcs = [
-        "internal/commandlineflag_test.cc",
+        "commandlineflag_test.cc",
     ],
     copts = ABSL_TEST_COPTS,
     linkopts = ABSL_DEFAULT_LINKOPTS,
     deps = [
+        ":commandlineflag",
         ":config",
         ":flag",
-        ":handle",
         ":private_handle_accessor",
         ":registry",
         "//absl/memory",
@@ -342,7 +352,6 @@ cc_test(
         ":config",
         ":flag",
         ":flag_internal",
-        ":handle",
         ":registry",
         "//absl/base:core_headers",
         "//absl/base:malloc_internal",
@@ -384,35 +393,35 @@ cc_test(
 )
 
 cc_test(
-    name = "path_util_test",
+    name = "parse_test",
     size = "small",
     srcs = [
-        "internal/path_util_test.cc",
+        "parse_test.cc",
     ],
     copts = ABSL_TEST_COPTS,
     linkopts = ABSL_DEFAULT_LINKOPTS,
     deps = [
-        ":path_util",
+        ":flag",
+        ":parse",
+        ":registry",
+        "//absl/base:raw_logging_internal",
+        "//absl/base:scoped_set_env",
+        "//absl/strings",
+        "//absl/types:span",
         "@com_google_googletest//:gtest_main",
     ],
 )
 
 cc_test(
-    name = "parse_test",
+    name = "path_util_test",
     size = "small",
     srcs = [
-        "parse_test.cc",
+        "internal/path_util_test.cc",
     ],
     copts = ABSL_TEST_COPTS,
     linkopts = ABSL_DEFAULT_LINKOPTS,
     deps = [
-        ":flag",
-        ":parse",
-        ":registry",
-        "//absl/base:raw_logging_internal",
-        "//absl/base:scoped_set_env",
-        "//absl/strings",
-        "//absl/types:span",
+        ":path_util",
         "@com_google_googletest//:gtest_main",
     ],
 )
@@ -442,7 +451,6 @@ cc_test(
     linkopts = ABSL_DEFAULT_LINKOPTS,
     deps = [
         ":flag",
-        ":handle",
         ":marshalling",
         ":registry",
         "//absl/memory",
diff --git a/absl/flags/CMakeLists.txt b/absl/flags/CMakeLists.txt
index e6b17c9b..6ecf3b48 100644
--- a/absl/flags/CMakeLists.txt
+++ b/absl/flags/CMakeLists.txt
@@ -17,24 +17,16 @@
 # Internal-only target, do not depend on directly.
 absl_cc_library(
   NAME
-    flags_internal
-  SRCS
-    "internal/flag.cc"
+    flags_path_util
   HDRS
-    "internal/flag.h"
+    "internal/path_util.h"
   COPTS
     ${ABSL_DEFAULT_COPTS}
   LINKOPTS
     ${ABSL_DEFAULT_LINKOPTS}
   DEPS
-    absl::base
     absl::config
-    absl::flags_config
-    absl::flags_handle
-    absl::flags_marshalling
-    absl::flags_registry
-    absl::synchronization
-    absl::meta
+    absl::strings
   PUBLIC
 )
 
@@ -59,22 +51,6 @@ absl_cc_library(
   PUBLIC
 )
 
-# Internal-only target, do not depend on directly.
-absl_cc_library(
-  NAME
-    flags_path_util
-  HDRS
-    "internal/path_util.h"
-  COPTS
-    ${ABSL_DEFAULT_COPTS}
-  LINKOPTS
-    ${ABSL_DEFAULT_LINKOPTS}
-  DEPS
-    absl::config
-    absl::strings
-  PUBLIC
-)
-
 absl_cc_library(
   NAME
     flags_config
@@ -118,9 +94,7 @@ absl_cc_library(
 # Internal-only target, do not depend on directly.
 absl_cc_library(
   NAME
-    flags_handle
-  SRCS
-    "internal/commandlineflag.cc"
+    flags_commandlineflag_internal
   HDRS
     "internal/commandlineflag.h"
   COPTS
@@ -129,12 +103,25 @@ absl_cc_library(
     ${ABSL_DEFAULT_LINKOPTS}
   DEPS
     absl::config
-    absl::fast_type_id
     absl::core_headers
-    absl::optional
-    absl::raw_logging_internal
+    absl::fast_type_id
     absl::strings
-    absl::synchronization
+)
+
+absl_cc_library(
+  NAME
+    flags_commandlineflag
+  SRCS
+    "commandlineflag.cc"
+  HDRS
+    "commandlineflag.h"
+  COPTS
+    ${ABSL_DEFAULT_COPTS}
+  LINKOPTS
+    ${ABSL_DEFAULT_LINKOPTS}
+  DEPS
+    absl::flags_commandlineflag_internal
+    absl::optional
 )
 
 # Internal-only target, do not depend on directly.
@@ -150,7 +137,7 @@ absl_cc_library(
   LINKOPTS
     ${ABSL_DEFAULT_LINKOPTS}
   DEPS
-    absl::flags_handle
+    absl::flags_commandlineflag
 )
 
 # Internal-only target, do not depend on directly.
@@ -169,8 +156,8 @@ absl_cc_library(
     ${ABSL_DEFAULT_LINKOPTS}
   DEPS
     absl::config
+    absl::flags_commandlineflag
     absl::flags_config
-    absl::flags_handle
     absl::flags_private_handle_accessor
     absl::core_headers
     absl::raw_logging_internal
@@ -178,6 +165,29 @@ absl_cc_library(
     absl::synchronization
 )
 
+# Internal-only target, do not depend on directly.
+absl_cc_library(
+  NAME
+    flags_internal
+  SRCS
+    "internal/flag.cc"
+  HDRS
+    "internal/flag.h"
+  COPTS
+    ${ABSL_DEFAULT_COPTS}
+  LINKOPTS
+    ${ABSL_DEFAULT_LINKOPTS}
+  DEPS
+    absl::base
+    absl::config
+    absl::flags_config
+    absl::flags_marshalling
+    absl::flags_registry
+    absl::synchronization
+    absl::meta
+  PUBLIC
+)
+
 absl_cc_library(
   NAME
     flags
@@ -192,8 +202,8 @@ absl_cc_library(
     ${ABSL_DEFAULT_LINKOPTS}
   DEPS
     absl::config
+    absl::flags_commandlineflag
     absl::flags_config
-    absl::flags_handle
     absl::flags_internal
     absl::flags_marshalling
     absl::flags_registry
@@ -218,10 +228,10 @@ absl_cc_library(
     absl::config
     absl::flags_config
     absl::flags
-    absl::flags_handle
-    absl::flags_private_handle_accessor
+    absl::flags_commandlineflag
     absl::flags_internal
     absl::flags_path_util
+    absl::flags_private_handle_accessor
     absl::flags_program_name
     absl::flags_registry
     absl::strings
@@ -264,9 +274,9 @@ absl_cc_library(
     absl::core_headers
     absl::flags_config
     absl::flags
-    absl::flags_handle
-    absl::flags_private_handle_accessor
+    absl::flags_commandlineflag
     absl::flags_internal
+    absl::flags_private_handle_accessor
     absl::flags_program_name
     absl::flags_registry
     absl::flags_usage
@@ -281,13 +291,13 @@ absl_cc_test(
   NAME
     flags_commandlineflag_test
   SRCS
-    "internal/commandlineflag_test.cc"
+    "commandlineflag_test.cc"
   COPTS
     ${ABSL_TEST_COPTS}
   DEPS
     absl::flags
+    absl::flags_commandlineflag
     absl::flags_config
-    absl::flags_handle
     absl::flags_private_handle_accessor
     absl::flags_registry
     absl::memory
@@ -319,7 +329,6 @@ absl_cc_test(
     absl::core_headers
     absl::flags
     absl::flags_config
-    absl::flags_handle
     absl::flags_internal
     absl::flags_registry
     absl::strings
@@ -391,7 +400,6 @@ absl_cc_test(
     ${ABSL_TEST_COPTS}
   DEPS
     absl::flags
-    absl::flags_handle
     absl::flags_marshalling
     absl::flags_registry
     absl::memory
diff --git a/absl/flags/internal/commandlineflag.cc b/absl/flags/commandlineflag.cc
index 84112437..83d14c1b 100644
--- a/absl/flags/internal/commandlineflag.cc
+++ b/absl/flags/commandlineflag.cc
@@ -13,21 +13,19 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
-#include "absl/flags/internal/commandlineflag.h"
+#include "absl/flags/commandlineflag.h"
 
 namespace absl {
 ABSL_NAMESPACE_BEGIN
-namespace flags_internal {
-
-FlagStateInterface::~FlagStateInterface() {}
 
 bool CommandLineFlag::IsRetired() const { return false; }
-
 bool CommandLineFlag::ParseFrom(absl::string_view value, std::string* error) {
   return ParseFrom(value, flags_internal::SET_FLAGS_VALUE,
                    flags_internal::kProgrammaticChange, error);
 }
 
+namespace flags_internal {
+FlagStateInterface::~FlagStateInterface() {}
 }  // namespace flags_internal
 ABSL_NAMESPACE_END
 }  // namespace absl
diff --git a/absl/flags/commandlineflag.h b/absl/flags/commandlineflag.h
new file mode 100644
index 00000000..f09f1f70
--- /dev/null
+++ b/absl/flags/commandlineflag.h
@@ -0,0 +1,190 @@
+//
+// 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.
+//
+// -----------------------------------------------------------------------------
+// File: commandlineflag.h
+// -----------------------------------------------------------------------------
+//
+// This header file defines the `CommandLineFlag`, which acts as a type-erased
+// handle for accessing metadata about the Abseil Flag in question.
+//
+// Because an actual Abseil flag is of an unspecified type, you should not
+// manipulate or interact directly with objects of that type. Instead, use the
+// CommandLineFlag type as an intermediary.
+#ifndef ABSL_FLAGS_COMMANDLINEFLAG_H_
+#define ABSL_FLAGS_COMMANDLINEFLAG_H_
+
+#include "absl/flags/internal/commandlineflag.h"
+#include "absl/types/optional.h"
+
+namespace absl {
+ABSL_NAMESPACE_BEGIN
+namespace flags_internal {
+class PrivateHandleAccessor;
+}  // namespace flags_internal
+
+// CommandLineFlag
+//
+// This type acts as a type-erased handle for an instance of an Abseil Flag and
+// holds reflection information pertaining to that flag. Use CommandLineFlag to
+// access a flag's name, location, help string etc.
+//
+// To obtain an absl::CommandLineFlag, invoke `absl::FindCommandLineFlag()`
+// passing it the flag name string.
+//
+// Example:
+//
+//   // Obtain reflection handle for a flag named "flagname".
+//   const absl::CommandLineFlag* my_flag_data =
+//        absl::FindCommandLineFlag("flagname");
+//
+//   // Now you can get flag info from that reflection handle.
+//   std::string flag_location = my_flag_data->Filename();
+//   ...
+class CommandLineFlag {
+ public:
+  constexpr CommandLineFlag() = default;
+
+  // Not copyable/assignable.
+  CommandLineFlag(const CommandLineFlag&) = delete;
+  CommandLineFlag& operator=(const CommandLineFlag&) = delete;
+
+  // absl::CommandLineFlag::IsOfType()
+  //
+  // Return true iff flag has type T.
+  template <typename T>
+  inline bool IsOfType() const {
+    return TypeId() == base_internal::FastTypeId<T>();
+  }
+
+  // absl::CommandLineFlag::TryGet()
+  //
+  // Attempts to retrieve the flag value. Returns value on success,
+  // absl::nullopt otherwise.
+  template <typename T>
+  absl::optional<T> TryGet() const {
+    if (IsRetired() || !IsOfType<T>()) {
+      return absl::nullopt;
+    }
+
+    // Implementation notes:
+    //
+    // We are wrapping a union around the value of `T` to serve three purposes:
+    //
+    //  1. `U.value` has correct size and alignment for a value of type `T`
+    //  2. The `U.value` constructor is not invoked since U's constructor does
+    //     not do it explicitly.
+    //  3. The `U.value` destructor is invoked since U's destructor does it
+    //     explicitly. This makes `U` a kind of RAII wrapper around non default
+    //     constructible value of T, which is destructed when we leave the
+    //     scope. We do need to destroy U.value, which is constructed by
+    //     CommandLineFlag::Read even though we left it in a moved-from state
+    //     after std::move.
+    //
+    // All of this serves to avoid requiring `T` being default constructible.
+    union U {
+      T value;
+      U() {}
+      ~U() { value.~T(); }
+    };
+    U u;
+
+    Read(&u.value);
+    return std::move(u.value);
+  }
+
+  // absl::CommandLineFlag::Name()
+  //
+  // Returns name of this flag.
+  virtual absl::string_view Name() const = 0;
+
+  // absl::CommandLineFlag::Filename()
+  //
+  // Returns name of the file where this flag is defined.
+  virtual std::string Filename() const = 0;
+
+  // absl::CommandLineFlag::Help()
+  //
+  // Returns help message associated with this flag.
+  virtual std::string Help() const = 0;
+
+  // absl::CommandLineFlag::IsRetired()
+  //
+  // Returns true iff this object corresponds to retired flag.
+  virtual bool IsRetired() const;
+
+  // absl::CommandLineFlag::DefaultValue()
+  //
+  // Returns the default value for this flag.
+  virtual std::string DefaultValue() const = 0;
+
+  // absl::CommandLineFlag::CurrentValue()
+  //
+  // Returns the current value for this flag.
+  virtual std::string CurrentValue() const = 0;
+
+  // absl::CommandLineFlag::ParseFrom()
+  //
+  // Sets the value of the flag based on specified string `value`. If the flag
+  // was successfully set to new value, it returns true. Otherwise, sets `error`
+  // to indicate the error, leaves the flag unchanged, and returns false.
+  bool ParseFrom(absl::string_view value, std::string* error);
+
+ protected:
+  ~CommandLineFlag() = default;
+
+ private:
+  friend class flags_internal::PrivateHandleAccessor;
+
+  // Sets the value of the flag based on specified string `value`. If the flag
+  // was successfully set to new value, it returns true. Otherwise, sets `error`
+  // to indicate the error, leaves the flag unchanged, and returns false. There
+  // are three ways to set the flag's value:
+  //  * Update the current flag value
+  //  * Update the flag's default value
+  //  * Update the current flag value if it was never set before
+  // The mode is selected based on `set_mode` parameter.
+  virtual bool ParseFrom(absl::string_view value,
+                         flags_internal::FlagSettingMode set_mode,
+                         flags_internal::ValueSource source,
+                         std::string* error) = 0;
+
+  // Returns id of the flag's value type.
+  virtual flags_internal::FlagFastTypeId TypeId() const = 0;
+
+  // Interface to save flag to some persistent state. Returns current flag state
+  // or nullptr if flag does not support saving and restoring a state.
+  virtual std::unique_ptr<flags_internal::FlagStateInterface> SaveState() = 0;
+
+  // Copy-construct a new value of the flag's type in a memory referenced by
+  // the dst based on the current flag's value.
+  virtual void Read(void* dst) const = 0;
+
+  // To be deleted. Used to return true if flag's current value originated from
+  // command line.
+  virtual bool IsSpecifiedOnCommandLine() const = 0;
+
+  // Validates supplied value usign validator or parseflag routine
+  virtual bool ValidateInputValue(absl::string_view value) const = 0;
+
+  // Checks that flags default value can be converted to string and back to the
+  // flag's value type.
+  virtual void CheckDefaultValueParsingRoundtrip() const = 0;
+};
+
+ABSL_NAMESPACE_END
+}  // namespace absl
+
+#endif  // ABSL_FLAGS_COMMANDLINEFLAG_H_
diff --git a/absl/flags/internal/commandlineflag_test.cc b/absl/flags/commandlineflag_test.cc
index 0b5aea37..352edccf 100644
--- a/absl/flags/internal/commandlineflag_test.cc
+++ b/absl/flags/commandlineflag_test.cc
@@ -13,7 +13,7 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
-#include "absl/flags/internal/commandlineflag.h"
+#include "absl/flags/commandlineflag.h"
 
 #include <memory>
 #include <string>
@@ -70,9 +70,10 @@ TEST_F(CommandLineFlagTest, TestAttributesAccessMethods) {
   EXPECT_EQ(flag_01->Help(), "int_flag help");
   EXPECT_TRUE(!flag_01->IsRetired());
   EXPECT_TRUE(flag_01->IsOfType<int>());
-  EXPECT_TRUE(
-      absl::EndsWith(flag_01->Filename(),
-                     "absl/flags/internal/commandlineflag_test.cc"))
+  EXPECT_TRUE(!flag_01->IsOfType<bool>());
+  EXPECT_TRUE(!flag_01->IsOfType<std::string>());
+  EXPECT_TRUE(absl::EndsWith(flag_01->Filename(),
+                             "absl/flags/commandlineflag_test.cc"))
       << flag_01->Filename();
 
   auto* flag_02 = flags::FindCommandLineFlag("string_flag");
@@ -82,9 +83,10 @@ TEST_F(CommandLineFlagTest, TestAttributesAccessMethods) {
   EXPECT_EQ(flag_02->Help(), "string_flag help");
   EXPECT_TRUE(!flag_02->IsRetired());
   EXPECT_TRUE(flag_02->IsOfType<std::string>());
-  EXPECT_TRUE(
-      absl::EndsWith(flag_02->Filename(),
-                     "absl/flags/internal/commandlineflag_test.cc"))
+  EXPECT_TRUE(!flag_02->IsOfType<bool>());
+  EXPECT_TRUE(!flag_02->IsOfType<int>());
+  EXPECT_TRUE(absl::EndsWith(flag_02->Filename(),
+                             "absl/flags/commandlineflag_test.cc"))
       << flag_02->Filename();
 
   auto* flag_03 = flags::FindRetiredFlag("bool_retired_flag");
@@ -94,6 +96,8 @@ TEST_F(CommandLineFlagTest, TestAttributesAccessMethods) {
   EXPECT_EQ(flag_03->Help(), "");
   EXPECT_TRUE(flag_03->IsRetired());
   EXPECT_TRUE(flag_03->IsOfType<bool>());
+  EXPECT_TRUE(!flag_03->IsOfType<int>());
+  EXPECT_TRUE(!flag_03->IsOfType<std::string>());
   EXPECT_EQ(flag_03->Filename(), "RETIRED");
 }
 
diff --git a/absl/flags/flag.cc b/absl/flags/flag.cc
index f7a457bf..531df128 100644
--- a/absl/flags/flag.cc
+++ b/absl/flags/flag.cc
@@ -16,8 +16,6 @@
 #include "absl/flags/flag.h"
 
 #include "absl/base/config.h"
-#include "absl/flags/internal/commandlineflag.h"
-#include "absl/flags/internal/flag.h"
 
 namespace absl {
 ABSL_NAMESPACE_BEGIN
diff --git a/absl/flags/flag.h b/absl/flags/flag.h
index ca7d581f..f84853ea 100644
--- a/absl/flags/flag.h
+++ b/absl/flags/flag.h
@@ -37,7 +37,6 @@
 #include "absl/base/config.h"
 #include "absl/flags/config.h"
 #include "absl/flags/declare.h"
-#include "absl/flags/internal/commandlineflag.h"
 #include "absl/flags/internal/flag.h"
 #include "absl/flags/internal/registry.h"
 #include "absl/flags/marshalling.h"
@@ -265,27 +264,29 @@ ABSL_NAMESPACE_END
 // -----------------------------------------------------------------------------
 
 // ABSL_FLAG_IMPL macro definition conditional on ABSL_FLAGS_STRIP_NAMES
+#if !defined(_MSC_VER) || defined(__clang__)
+#define ABSL_FLAG_IMPL_FLAG_PTR(flag) &flag
+#define ABSL_FLAG_IMPL_HELP_ARG(name)                      \
+  absl::flags_internal::HelpArg<AbslFlagHelpGenFor##name>( \
+      FLAGS_help_storage_##name)
+#define ABSL_FLAG_IMPL_DEFAULT_ARG(Type, name) \
+  absl::flags_internal::DefaultArg<Type, AbslFlagDefaultGenFor##name>(0)
+#else
+#define ABSL_FLAG_IMPL_FLAG_PTR(flag) flag.GetImpl()
+#define ABSL_FLAG_IMPL_HELP_ARG(name) &AbslFlagHelpGenFor##name::NonConst
+#define ABSL_FLAG_IMPL_DEFAULT_ARG(Type, name) &AbslFlagDefaultGenFor##name::Gen
+#endif
 
 #if ABSL_FLAGS_STRIP_NAMES
 #define ABSL_FLAG_IMPL_FLAGNAME(txt) ""
 #define ABSL_FLAG_IMPL_FILENAME() ""
-#if !defined(_MSC_VER) || defined(__clang__)
 #define ABSL_FLAG_IMPL_REGISTRAR(T, flag) \
-  absl::flags_internal::FlagRegistrar<T, false>(&flag)
-#else
-#define ABSL_FLAG_IMPL_REGISTRAR(T, flag) \
-  absl::flags_internal::FlagRegistrar<T, false>(flag.GetImpl())
-#endif
+  absl::flags_internal::FlagRegistrar<T, false>(ABSL_FLAG_IMPL_FLAG_PTR(flag))
 #else
 #define ABSL_FLAG_IMPL_FLAGNAME(txt) txt
 #define ABSL_FLAG_IMPL_FILENAME() __FILE__
-#if !defined(_MSC_VER) || defined(__clang__)
-#define ABSL_FLAG_IMPL_REGISTRAR(T, flag) \
-  absl::flags_internal::FlagRegistrar<T, true>(&flag)
-#else
 #define ABSL_FLAG_IMPL_REGISTRAR(T, flag) \
-  absl::flags_internal::FlagRegistrar<T, true>(flag.GetImpl())
-#endif
+  absl::flags_internal::FlagRegistrar<T, true>(ABSL_FLAG_IMPL_FLAG_PTR(flag))
 #endif
 
 // ABSL_FLAG_IMPL macro definition conditional on ABSL_FLAGS_STRIP_HELP
@@ -301,15 +302,24 @@ ABSL_NAMESPACE_END
 // between the two via the call to HelpArg in absl::Flag instantiation below.
 // If help message expression is constexpr evaluable compiler will optimize
 // away this whole struct.
-#define ABSL_FLAG_IMPL_DECLARE_HELP_WRAPPER(name, txt)                     \
-  struct AbslFlagHelpGenFor##name {                                        \
-    template <typename T = void>                                           \
-    static constexpr const char* Const() {                                 \
-      return absl::flags_internal::HelpConstexprWrap(                      \
-          ABSL_FLAG_IMPL_FLAGHELP(txt));                                   \
-    }                                                                      \
-    static std::string NonConst() { return ABSL_FLAG_IMPL_FLAGHELP(txt); } \
-  }
+// TODO(rogeeff): place these generated structs into local namespace and apply
+// ABSL_INTERNAL_UNIQUE_SHORT_NAME.
+// TODO(rogeeff): Apply __attribute__((nodebug)) to FLAGS_help_storage_##name
+#define ABSL_FLAG_IMPL_DECLARE_HELP_WRAPPER(name, txt)                       \
+  struct AbslFlagHelpGenFor##name {                                          \
+    /* The expression is run in the caller as part of the   */               \
+    /* default value argument. That keeps temporaries alive */               \
+    /* long enough for NonConst to work correctly.          */               \
+    static constexpr absl::string_view Value(                                \
+        absl::string_view v = ABSL_FLAG_IMPL_FLAGHELP(txt)) {                \
+      return v;                                                              \
+    }                                                                        \
+    static std::string NonConst() { return std::string(Value()); }           \
+  };                                                                         \
+  constexpr auto FLAGS_help_storage_##name ABSL_INTERNAL_UNIQUE_SMALL_NAME() \
+      ABSL_ATTRIBUTE_SECTION_VARIABLE(flags_help_cold) =                     \
+          absl::flags_internal::HelpStringAsArray<AbslFlagHelpGenFor##name>( \
+              0);
 
 #define ABSL_FLAG_IMPL_DECLARE_DEF_VAL_WRAPPER(name, Type, default_value)     \
   struct AbslFlagDefaultGenFor##name {                                        \
@@ -317,40 +327,23 @@ ABSL_NAMESPACE_END
     static void Gen(void* p) {                                                \
       new (p) Type(AbslFlagDefaultGenFor##name{}.value);                      \
     }                                                                         \
-  }
+  };
 
 // ABSL_FLAG_IMPL
 //
 // Note: Name of registrar object is not arbitrary. It is used to "grab"
 // global name for FLAGS_no<flag_name> symbol, thus preventing the possibility
 // of defining two flags with names foo and nofoo.
-#if !defined(_MSC_VER) || defined(__clang__)
-
-#define ABSL_FLAG_IMPL(Type, name, default_value, help)                        \
-  namespace absl /* block flags in namespaces */ {}                            \
-  ABSL_FLAG_IMPL_DECLARE_DEF_VAL_WRAPPER(name, Type, default_value);           \
-  ABSL_FLAG_IMPL_DECLARE_HELP_WRAPPER(name, help);                             \
-  ABSL_CONST_INIT absl::Flag<Type> FLAGS_##name{                               \
-      ABSL_FLAG_IMPL_FLAGNAME(#name), ABSL_FLAG_IMPL_FILENAME(),               \
-      absl::flags_internal::HelpArg<AbslFlagHelpGenFor##name>(0),              \
-      absl::flags_internal::DefaultArg<Type, AbslFlagDefaultGenFor##name>(0)}; \
-  extern absl::flags_internal::FlagRegistrarEmpty FLAGS_no##name;              \
-  absl::flags_internal::FlagRegistrarEmpty FLAGS_no##name =                    \
-      ABSL_FLAG_IMPL_REGISTRAR(Type, FLAGS_##name)
-#else
-// MSVC version uses aggregate initialization. We also do not try to
-// optimize away help wrapper.
-#define ABSL_FLAG_IMPL(Type, name, default_value, help)                        \
-  namespace absl /* block flags in namespaces */ {}                            \
-  ABSL_FLAG_IMPL_DECLARE_DEF_VAL_WRAPPER(name, Type, default_value);           \
-  ABSL_FLAG_IMPL_DECLARE_HELP_WRAPPER(name, help);                             \
-  ABSL_CONST_INIT absl::Flag<Type> FLAGS_##name{                               \
-      ABSL_FLAG_IMPL_FLAGNAME(#name), ABSL_FLAG_IMPL_FILENAME(),               \
-      &AbslFlagHelpGenFor##name::NonConst, &AbslFlagDefaultGenFor##name::Gen}; \
-  extern absl::flags_internal::FlagRegistrarEmpty FLAGS_no##name;              \
-  absl::flags_internal::FlagRegistrarEmpty FLAGS_no##name =                    \
+#define ABSL_FLAG_IMPL(Type, name, default_value, help)                       \
+  namespace absl /* block flags in namespaces */ {}                           \
+  ABSL_FLAG_IMPL_DECLARE_DEF_VAL_WRAPPER(name, Type, default_value)           \
+  ABSL_FLAG_IMPL_DECLARE_HELP_WRAPPER(name, help)                             \
+  ABSL_CONST_INIT absl::Flag<Type> FLAGS_##name{                              \
+      ABSL_FLAG_IMPL_FLAGNAME(#name), ABSL_FLAG_IMPL_FILENAME(),              \
+      ABSL_FLAG_IMPL_HELP_ARG(name), ABSL_FLAG_IMPL_DEFAULT_ARG(Type, name)}; \
+  extern absl::flags_internal::FlagRegistrarEmpty FLAGS_no##name;             \
+  absl::flags_internal::FlagRegistrarEmpty FLAGS_no##name =                   \
       ABSL_FLAG_IMPL_REGISTRAR(Type, FLAGS_##name)
-#endif
 
 // ABSL_RETIRED_FLAG
 //
diff --git a/absl/flags/flag_test.cc b/absl/flags/flag_test.cc
index 416a31e5..8d53ecd6 100644
--- a/absl/flags/flag_test.cc
+++ b/absl/flags/flag_test.cc
@@ -26,7 +26,6 @@
 #include "absl/base/attributes.h"
 #include "absl/flags/config.h"
 #include "absl/flags/declare.h"
-#include "absl/flags/internal/commandlineflag.h"
 #include "absl/flags/internal/flag.h"
 #include "absl/flags/internal/registry.h"
 #include "absl/flags/usage_config.h"
diff --git a/absl/flags/internal/commandlineflag.h b/absl/flags/internal/commandlineflag.h
index fa050209..3c149788 100644
--- a/absl/flags/internal/commandlineflag.h
+++ b/absl/flags/internal/commandlineflag.h
@@ -23,7 +23,6 @@
 #include "absl/base/internal/fast_type_id.h"
 #include "absl/base/macros.h"
 #include "absl/strings/string_view.h"
-#include "absl/types/optional.h"
 
 namespace absl {
 ABSL_NAMESPACE_BEGIN
@@ -67,117 +66,6 @@ class FlagStateInterface {
   virtual void Restore() const = 0;
 };
 
-// Holds all information for a flag.
-class CommandLineFlag {
- public:
-  constexpr CommandLineFlag() = default;
-
-  // Not copyable/assignable.
-  CommandLineFlag(const CommandLineFlag&) = delete;
-  CommandLineFlag& operator=(const CommandLineFlag&) = delete;
-
-  // Non-polymorphic access methods.
-
-  // Return true iff flag has type T.
-  template <typename T>
-  inline bool IsOfType() const {
-    return TypeId() == base_internal::FastTypeId<T>();
-  }
-
-  // Attempts to retrieve the flag value. Returns value on success,
-  // absl::nullopt otherwise.
-  template <typename T>
-  absl::optional<T> TryGet() const {
-    if (IsRetired() || !IsOfType<T>()) {
-      return absl::nullopt;
-    }
-
-    // Implementation notes:
-    //
-    // We are wrapping a union around the value of `T` to serve three purposes:
-    //
-    //  1. `U.value` has correct size and alignment for a value of type `T`
-    //  2. The `U.value` constructor is not invoked since U's constructor does
-    //     not do it explicitly.
-    //  3. The `U.value` destructor is invoked since U's destructor does it
-    //     explicitly. This makes `U` a kind of RAII wrapper around non default
-    //     constructible value of T, which is destructed when we leave the
-    //     scope. We do need to destroy U.value, which is constructed by
-    //     CommandLineFlag::Read even though we left it in a moved-from state
-    //     after std::move.
-    //
-    // All of this serves to avoid requiring `T` being default constructible.
-    union U {
-      T value;
-      U() {}
-      ~U() { value.~T(); }
-    };
-    U u;
-
-    Read(&u.value);
-    return std::move(u.value);
-  }
-
-  // Polymorphic access methods
-
-  // Returns name of this flag.
-  virtual absl::string_view Name() const = 0;
-  // Returns name of the file where this flag is defined.
-  virtual std::string Filename() const = 0;
-  // Returns help message associated with this flag.
-  virtual std::string Help() const = 0;
-  // Returns true iff this object corresponds to retired flag.
-  virtual bool IsRetired() const;
-  virtual std::string DefaultValue() const = 0;
-  virtual std::string CurrentValue() const = 0;
-
-  // Sets the value of the flag based on specified string `value`. If the flag
-  // was successfully set to new value, it returns true. Otherwise, sets `error`
-  // to indicate the error, leaves the flag unchanged, and returns false.
-  bool ParseFrom(absl::string_view value, std::string* error);
-
- protected:
-  ~CommandLineFlag() = default;
-
- private:
-  friend class PrivateHandleAccessor;
-
-  // Sets the value of the flag based on specified string `value`. If the flag
-  // was successfully set to new value, it returns true. Otherwise, sets `error`
-  // to indicate the error, leaves the flag unchanged, and returns false. There
-  // are three ways to set the flag's value:
-  //  * Update the current flag value
-  //  * Update the flag's default value
-  //  * Update the current flag value if it was never set before
-  // The mode is selected based on `set_mode` parameter.
-  virtual bool ParseFrom(absl::string_view value,
-                         flags_internal::FlagSettingMode set_mode,
-                         flags_internal::ValueSource source,
-                         std::string* error) = 0;
-
-  // Returns id of the flag's value type.
-  virtual FlagFastTypeId TypeId() const = 0;
-
-  // Interface to save flag to some persistent state. Returns current flag state
-  // or nullptr if flag does not support saving and restoring a state.
-  virtual std::unique_ptr<FlagStateInterface> SaveState() = 0;
-
-  // Copy-construct a new value of the flag's type in a memory referenced by
-  // the dst based on the current flag's value.
-  virtual void Read(void* dst) const = 0;
-
-  // To be deleted. Used to return true if flag's current value originated from
-  // command line.
-  virtual bool IsSpecifiedOnCommandLine() const = 0;
-
-  // Validates supplied value usign validator or parseflag routine
-  virtual bool ValidateInputValue(absl::string_view value) const = 0;
-
-  // Checks that flags default value can be converted to string and back to the
-  // flag's value type.
-  virtual void CheckDefaultValueParsingRoundtrip() const = 0;
-};
-
 }  // namespace flags_internal
 ABSL_NAMESPACE_END
 }  // namespace absl
diff --git a/absl/flags/internal/flag.cc b/absl/flags/internal/flag.cc
index 96c026dc..35ae55fb 100644
--- a/absl/flags/internal/flag.cc
+++ b/absl/flags/internal/flag.cc
@@ -29,7 +29,6 @@
 #include "absl/base/config.h"
 #include "absl/base/const_init.h"
 #include "absl/base/optimization.h"
-#include "absl/flags/internal/commandlineflag.h"
 #include "absl/flags/usage_config.h"
 #include "absl/strings/str_cat.h"
 #include "absl/strings/string_view.h"
diff --git a/absl/flags/internal/flag.h b/absl/flags/internal/flag.h
index e374ecde..97ddb5f9 100644
--- a/absl/flags/internal/flag.h
+++ b/absl/flags/internal/flag.h
@@ -28,8 +28,8 @@
 #include "absl/base/call_once.h"
 #include "absl/base/config.h"
 #include "absl/base/thread_annotations.h"
+#include "absl/flags/commandlineflag.h"
 #include "absl/flags/config.h"
-#include "absl/flags/internal/commandlineflag.h"
 #include "absl/flags/internal/registry.h"
 #include "absl/flags/marshalling.h"
 #include "absl/memory/memory.h"
@@ -168,6 +168,28 @@ inline const std::type_info* GenRuntimeTypeId() {
 // cases.
 using HelpGenFunc = std::string (*)();
 
+template <size_t N>
+struct FixedCharArray {
+  char value[N];
+
+  template <size_t... I>
+  static constexpr FixedCharArray<N> FromLiteralString(
+      absl::string_view str, absl::index_sequence<I...>) {
+    return (void)str, FixedCharArray<N>({{str[I]..., '\0'}});
+  }
+};
+
+template <typename Gen, size_t N = Gen::Value().size()>
+constexpr FixedCharArray<N + 1> HelpStringAsArray(int) {
+  return FixedCharArray<N + 1>::FromLiteralString(
+      Gen::Value(), absl::make_index_sequence<N>{});
+}
+
+template <typename Gen>
+constexpr std::false_type HelpStringAsArray(char) {
+  return std::false_type{};
+}
+
 union FlagHelpMsg {
   constexpr explicit FlagHelpMsg(const char* help_msg) : literal(help_msg) {}
   constexpr explicit FlagHelpMsg(HelpGenFunc help_gen) : gen_func(help_gen) {}
@@ -185,40 +207,28 @@ struct FlagHelpArg {
 
 extern const char kStrippedFlagHelp[];
 
-// HelpConstexprWrap is used by struct AbslFlagHelpGenFor##name generated by
-// ABSL_FLAG macro. It is only used to silence the compiler in the case where
-// help message expression is not constexpr and does not have type const char*.
-// If help message expression is indeed constexpr const char* HelpConstexprWrap
-// is just a trivial identity function.
-template <typename T>
-const char* HelpConstexprWrap(const T&) {
-  return nullptr;
-}
-constexpr const char* HelpConstexprWrap(const char* p) { return p; }
-constexpr const char* HelpConstexprWrap(char* p) { return p; }
-
 // These two HelpArg overloads allows us to select at compile time one of two
 // way to pass Help argument to absl::Flag. We'll be passing
-// AbslFlagHelpGenFor##name as T and integer 0 as a single argument to prefer
-// first overload if possible. If T::Const is evaluatable on constexpr
-// context (see non template int parameter below) we'll choose first overload.
-// In this case the help message expression is immediately evaluated and is used
-// to construct the absl::Flag. No additionl code is generated by ABSL_FLAG.
-// Otherwise SFINAE kicks in and first overload is dropped from the
+// AbslFlagHelpGenFor##name as Gen and integer 0 as a single argument to prefer
+// first overload if possible. If help message is evaluatable on constexpr
+// context We'll be able to make FixedCharArray out of it and we'll choose first
+// overload. In this case the help message expression is immediately evaluated
+// and is used to construct the absl::Flag. No additionl code is generated by
+// ABSL_FLAG Otherwise SFINAE kicks in and first overload is dropped from the
 // consideration, in which case the second overload will be used. The second
 // overload does not attempt to evaluate the help message expression
 // immediately and instead delays the evaluation by returing the function
 // pointer (&T::NonConst) genering the help message when necessary. This is
 // evaluatable in constexpr context, but the cost is an extra function being
 // generated in the ABSL_FLAG code.
-template <typename T, int = (T::Const(), 1)>
-constexpr FlagHelpArg HelpArg(int) {
-  return {FlagHelpMsg(T::Const()), FlagHelpKind::kLiteral};
+template <typename Gen, size_t N>
+constexpr FlagHelpArg HelpArg(const FixedCharArray<N>& value) {
+  return {FlagHelpMsg(value.value), FlagHelpKind::kLiteral};
 }
 
-template <typename T>
-constexpr FlagHelpArg HelpArg(char) {
-  return {FlagHelpMsg(&T::NonConst), FlagHelpKind::kGenFunc};
+template <typename Gen>
+constexpr FlagHelpArg HelpArg(std::false_type) {
+  return {FlagHelpMsg(&Gen::NonConst), FlagHelpKind::kGenFunc};
 }
 
 ///////////////////////////////////////////////////////////////////////////////
@@ -419,7 +429,7 @@ struct DynValueDeleter {
 
 class FlagState;
 
-class FlagImpl final : public flags_internal::CommandLineFlag {
+class FlagImpl final : public CommandLineFlag {
  public:
   constexpr FlagImpl(const char* name, const char* filename, FlagOpFn op,
                      FlagHelpArg help, FlagValueStorageKind value_kind,
diff --git a/absl/flags/internal/private_handle_accessor.h b/absl/flags/internal/private_handle_accessor.h
index 40591de4..07838600 100644
--- a/absl/flags/internal/private_handle_accessor.h
+++ b/absl/flags/internal/private_handle_accessor.h
@@ -16,7 +16,7 @@
 #ifndef ABSL_FLAGS_INTERNAL_PRIVATE_HANDLE_ACCESSOR_H_
 #define ABSL_FLAGS_INTERNAL_PRIVATE_HANDLE_ACCESSOR_H_
 
-#include "absl/flags/internal/commandlineflag.h"
+#include "absl/flags/commandlineflag.h"
 
 namespace absl {
 ABSL_NAMESPACE_BEGIN
diff --git a/absl/flags/internal/registry.cc b/absl/flags/internal/registry.cc
index 3b941f04..70d76557 100644
--- a/absl/flags/internal/registry.cc
+++ b/absl/flags/internal/registry.cc
@@ -28,7 +28,7 @@
 #include "absl/base/config.h"
 #include "absl/base/internal/raw_logging.h"
 #include "absl/base/thread_annotations.h"
-#include "absl/flags/internal/commandlineflag.h"
+#include "absl/flags/commandlineflag.h"
 #include "absl/flags/internal/private_handle_accessor.h"
 #include "absl/flags/usage_config.h"
 #include "absl/strings/str_cat.h"
@@ -111,6 +111,7 @@ class FlagRegistryLock {
 };
 
 void DestroyRetiredFlag(CommandLineFlag* flag);
+
 }  // namespace
 
 void FlagRegistry::RegisterFlag(CommandLineFlag* flag) {
@@ -205,7 +206,7 @@ class FlagSaverImpl {
   // It's an error to call this more than once.
   void SaveFromRegistry() {
     assert(backup_registry_.empty());  // call only once!
-    flags_internal::ForEachFlag([&](flags_internal::CommandLineFlag* flag) {
+    flags_internal::ForEachFlag([&](CommandLineFlag* flag) {
       if (auto flag_state =
               flags_internal::PrivateHandleAccessor::SaveState(flag)) {
         backup_registry_.emplace_back(std::move(flag_state));
@@ -283,7 +284,7 @@ bool RegisterCommandLineFlag(CommandLineFlag* flag) {
 
 namespace {
 
-class RetiredFlagObj final : public flags_internal::CommandLineFlag {
+class RetiredFlagObj final : public CommandLineFlag {
  public:
   constexpr RetiredFlagObj(const char* name, FlagFastTypeId type_id)
       : name_(name), type_id_(type_id) {}
@@ -319,7 +320,7 @@ class RetiredFlagObj final : public flags_internal::CommandLineFlag {
   const FlagFastTypeId type_id_;
 };
 
-void DestroyRetiredFlag(flags_internal::CommandLineFlag* flag) {
+void DestroyRetiredFlag(CommandLineFlag* flag) {
   assert(flag->IsRetired());
   delete static_cast<RetiredFlagObj*>(flag);
 }
diff --git a/absl/flags/internal/registry.h b/absl/flags/internal/registry.h
index af8ed6b9..f722fd44 100644
--- a/absl/flags/internal/registry.h
+++ b/absl/flags/internal/registry.h
@@ -30,6 +30,8 @@
 
 namespace absl {
 ABSL_NAMESPACE_BEGIN
+class CommandLineFlag;
+
 namespace flags_internal {
 
 CommandLineFlag* FindCommandLineFlag(absl::string_view name);
diff --git a/absl/flags/internal/type_erased.cc b/absl/flags/internal/type_erased.cc
index c13fb9b0..35b0d125 100644
--- a/absl/flags/internal/type_erased.cc
+++ b/absl/flags/internal/type_erased.cc
@@ -21,7 +21,7 @@
 
 #include "absl/base/config.h"
 #include "absl/base/internal/raw_logging.h"
-#include "absl/flags/internal/commandlineflag.h"
+#include "absl/flags/commandlineflag.h"
 #include "absl/flags/internal/private_handle_accessor.h"
 #include "absl/flags/internal/registry.h"
 #include "absl/flags/usage_config.h"
diff --git a/absl/flags/internal/type_erased.h b/absl/flags/internal/type_erased.h
index b43a0ff7..fd9663e2 100644
--- a/absl/flags/internal/type_erased.h
+++ b/absl/flags/internal/type_erased.h
@@ -19,7 +19,7 @@
 #include <string>
 
 #include "absl/base/config.h"
-#include "absl/flags/internal/commandlineflag.h"
+#include "absl/flags/commandlineflag.h"
 #include "absl/flags/internal/registry.h"
 #include "absl/strings/string_view.h"
 
diff --git a/absl/flags/internal/type_erased_test.cc b/absl/flags/internal/type_erased_test.cc
index 4ce59810..bb0ff23e 100644
--- a/absl/flags/internal/type_erased_test.cc
+++ b/absl/flags/internal/type_erased_test.cc
@@ -20,7 +20,6 @@
 
 #include "gtest/gtest.h"
 #include "absl/flags/flag.h"
-#include "absl/flags/internal/commandlineflag.h"
 #include "absl/flags/internal/registry.h"
 #include "absl/flags/marshalling.h"
 #include "absl/memory/memory.h"
diff --git a/absl/flags/internal/usage.cc b/absl/flags/internal/usage.cc
index 10accc46..11664e10 100644
--- a/absl/flags/internal/usage.cc
+++ b/absl/flags/internal/usage.cc
@@ -23,8 +23,8 @@
 #include <vector>
 
 #include "absl/base/config.h"
+#include "absl/flags/commandlineflag.h"
 #include "absl/flags/flag.h"
-#include "absl/flags/internal/commandlineflag.h"
 #include "absl/flags/internal/flag.h"
 #include "absl/flags/internal/path_util.h"
 #include "absl/flags/internal/private_handle_accessor.h"
@@ -182,8 +182,7 @@ class FlagHelpPrettyPrinter {
   bool first_line_;
 };
 
-void FlagHelpHumanReadable(const flags_internal::CommandLineFlag& flag,
-                           std::ostream* out) {
+void FlagHelpHumanReadable(const CommandLineFlag& flag, std::ostream* out) {
   FlagHelpPrettyPrinter printer(80, out);  // Max line length is 80.
 
   // Flag name.
@@ -245,11 +244,10 @@ void FlagsHelpImpl(std::ostream& out, flags_internal::FlagKindFilter filter_cb,
   // This map is used to output matching flags grouped by package and file
   // name.
   std::map<std::string,
-           std::map<std::string,
-                    std::vector<const flags_internal::CommandLineFlag*>>>
+           std::map<std::string, std::vector<const CommandLineFlag*>>>
       matching_flags;
 
-  flags_internal::ForEachFlag([&](flags_internal::CommandLineFlag* flag) {
+  flags_internal::ForEachFlag([&](CommandLineFlag* flag) {
     std::string flag_filename = flag->Filename();
 
     // Ignore retired flags.
@@ -303,7 +301,7 @@ void FlagsHelpImpl(std::ostream& out, flags_internal::FlagKindFilter filter_cb,
 
 // --------------------------------------------------------------------
 // Produces the help message describing specific flag.
-void FlagHelp(std::ostream& out, const flags_internal::CommandLineFlag& flag,
+void FlagHelp(std::ostream& out, const CommandLineFlag& flag,
               HelpFormat format) {
   if (format == HelpFormat::kHumanReadable)
     flags_internal::FlagHelpHumanReadable(flag, &out);
diff --git a/absl/flags/internal/usage.h b/absl/flags/internal/usage.h
index 6b080fd1..0c62dc4b 100644
--- a/absl/flags/internal/usage.h
+++ b/absl/flags/internal/usage.h
@@ -20,8 +20,8 @@
 #include <string>
 
 #include "absl/base/config.h"
+#include "absl/flags/commandlineflag.h"
 #include "absl/flags/declare.h"
-#include "absl/flags/internal/commandlineflag.h"
 #include "absl/strings/string_view.h"
 
 // --------------------------------------------------------------------
@@ -37,7 +37,7 @@ enum class HelpFormat {
 };
 
 // Outputs the help message describing specific flag.
-void FlagHelp(std::ostream& out, const flags_internal::CommandLineFlag& flag,
+void FlagHelp(std::ostream& out, const CommandLineFlag& flag,
               HelpFormat format = HelpFormat::kHumanReadable);
 
 // Produces the help messages for all flags matching the filter. A flag matches
diff --git a/absl/flags/parse.cc b/absl/flags/parse.cc
index fbf42675..3f0a7a75 100644
--- a/absl/flags/parse.cc
+++ b/absl/flags/parse.cc
@@ -34,9 +34,9 @@
 #include "absl/base/config.h"
 #include "absl/base/const_init.h"
 #include "absl/base/thread_annotations.h"
+#include "absl/flags/commandlineflag.h"
 #include "absl/flags/config.h"
 #include "absl/flags/flag.h"
-#include "absl/flags/internal/commandlineflag.h"
 #include "absl/flags/internal/flag.h"
 #include "absl/flags/internal/parse.h"
 #include "absl/flags/internal/private_handle_accessor.h"