Remove workaround for older versions MSVC that did not support

constexpr Flag construction. These versions of MSVC are no longer
supported.

PiperOrigin-RevId: 595195773
Change-Id: Iaf2f01a2255fb24f3aadc26f09600543fffa9da5

8 files changed, 1 insertions, 192 deletions

diff --git a/absl/flags/BUILD.bazel b/absl/flags/BUILD.bazel
index 170d1ba8..ce0c00a2 100644
--- a/absl/flags/BUILD.bazel
+++ b/absl/flags/BUILD.bazel
@@ -229,10 +229,6 @@ cc_library(
 
 cc_library(
     name = "flag",
-    srcs = [
-        "flag.cc",
-        "internal/flag_msvc.inc",
-    ],
     hdrs = [
         "declare.h",
         "flag.h",
diff --git a/absl/flags/CMakeLists.txt b/absl/flags/CMakeLists.txt
index ddf2d4e7..44953124 100644
--- a/absl/flags/CMakeLists.txt
+++ b/absl/flags/CMakeLists.txt
@@ -201,12 +201,9 @@ absl_cc_library(
 absl_cc_library(
   NAME
     flags
-  SRCS
-    "flag.cc"
   HDRS
     "declare.h"
     "flag.h"
-    "internal/flag_msvc.inc"
   COPTS
     ${ABSL_DEFAULT_COPTS}
   LINKOPTS
diff --git a/absl/flags/declare.h b/absl/flags/declare.h
index d1437bb9..8d2a856e 100644
--- a/absl/flags/declare.h
+++ b/absl/flags/declare.h
@@ -40,13 +40,8 @@ class Flag;
 // Flag
 //
 // Forward declaration of the `absl::Flag` type for use in defining the macro.
-#if defined(_MSC_VER) && !defined(__clang__)
-template <typename T>
-class Flag;
-#else
 template <typename T>
 using Flag = flags_internal::Flag<T>;
-#endif
 
 ABSL_NAMESPACE_END
 }  // namespace absl
diff --git a/absl/flags/flag.cc b/absl/flags/flag.cc
deleted file mode 100644
index 531df128..00000000
--- a/absl/flags/flag.cc
+++ /dev/null
@@ -1,38 +0,0 @@
-//
-//  Copyright 2019 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.
-
-#include "absl/flags/flag.h"
-
-#include "absl/base/config.h"
-
-namespace absl {
-ABSL_NAMESPACE_BEGIN
-
-// This global mutex protects on-demand construction of flag objects in MSVC
-// builds.
-#if defined(_MSC_VER) && !defined(__clang__)
-
-namespace flags_internal {
-
-ABSL_CONST_INIT static absl::Mutex construction_guard(absl::kConstInit);
-
-absl::Mutex* GetGlobalConstructionGuard() { return &construction_guard; }
-
-}  // namespace flags_internal
-
-#endif
-
-ABSL_NAMESPACE_END
-}  // namespace absl
diff --git a/absl/flags/flag.h b/absl/flags/flag.h
index b7f94be7..06ea6932 100644
--- a/absl/flags/flag.h
+++ b/absl/flags/flag.h
@@ -71,12 +71,9 @@ ABSL_NAMESPACE_BEGIN
 // For type support of Abseil Flags, see the marshalling.h header file, which
 // discusses supported standard types, optional flags, and additional Abseil
 // type support.
-#if !defined(_MSC_VER) || defined(__clang__)
+
 template <typename T>
 using Flag = flags_internal::Flag<T>;
-#else
-#include "absl/flags/internal/flag_msvc.inc"
-#endif
 
 // GetFlag()
 //
@@ -196,18 +193,12 @@ 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) ""
diff --git a/absl/flags/flag_test.cc b/absl/flags/flag_test.cc
index f9cda02e..8d14ba8d 100644
--- a/absl/flags/flag_test.cc
+++ b/absl/flags/flag_test.cc
@@ -144,7 +144,6 @@ using String = std::string;
 using int128 = absl::int128;
 using uint128 = absl::uint128;
 
-#if !defined(_MSC_VER) || defined(__clang__)
 #define DEFINE_CONSTRUCTED_FLAG(T, dflt, dflt_kind)                        \
   constexpr flags::FlagDefaultArg f1default##T{                            \
       flags::FlagDefaultSrc{dflt}, flags::FlagDefaultKind::dflt_kind};     \
@@ -157,16 +156,6 @@ using uint128 = absl::uint128;
           flags::FlagDefaultKind::kGenFunc                                 \
     }                                                                      \
   }
-#else
-#define DEFINE_CONSTRUCTED_FLAG(T, dflt, dflt_kind)                    \
-  constexpr flags::FlagDefaultArg f1default##T{                        \
-      flags::FlagDefaultSrc{dflt}, flags::FlagDefaultKind::dflt_kind}; \
-  constexpr absl::Flag<T> f1##T{"f1", "file", &TestLiteralHelpMsg,     \
-                                &TestMakeDflt<T>};                     \
-  ABSL_CONST_INIT absl::Flag<T> f2##T {                                \
-    "f2", "file", &TestHelpMsg, &TestMakeDflt<T>                       \
-  }
-#endif
 
 DEFINE_CONSTRUCTED_FLAG(bool, true, kOneWord);
 DEFINE_CONSTRUCTED_FLAG(int16_t, 1, kOneWord);
diff --git a/absl/flags/internal/flag.h b/absl/flags/internal/flag.h
index b41f9a69..2e6e6b87 100644
--- a/absl/flags/internal/flag.h
+++ b/absl/flags/internal/flag.h
@@ -54,13 +54,8 @@ template <typename T>
 class Flag;
 }  // namespace flags_internal
 
-#if defined(_MSC_VER) && !defined(__clang__)
-template <typename T>
-class Flag;
-#else
 template <typename T>
 using Flag = flags_internal::Flag<T>;
-#endif
 
 template <typename T>
 ABSL_MUST_USE_RESULT T GetFlag(const absl::Flag<T>& flag);
diff --git a/absl/flags/internal/flag_msvc.inc b/absl/flags/internal/flag_msvc.inc
deleted file mode 100644
index 614d09fd..00000000
--- a/absl/flags/internal/flag_msvc.inc
+++ /dev/null
@@ -1,116 +0,0 @@
-//
-//  Copyright 2021 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.
-
-// Do not include this file directly.
-// Include absl/flags/flag.h instead.
-
-// MSVC debug builds do not implement initialization with constexpr constructors
-// correctly. To work around this we add a level of indirection, so that the
-// class `absl::Flag` contains an `internal::Flag*` (instead of being an alias
-// to that class) and dynamically allocates an instance when necessary. We also
-// forward all calls to internal::Flag methods via trampoline methods. In this
-// setup the `absl::Flag` class does not have constructor and virtual methods,
-// all the data members are public and thus MSVC is able to initialize it at
-// link time. To deal with multiple threads accessing the flag for the first
-// time concurrently we use an atomic boolean indicating if flag object is
-// initialized. We also employ the double-checked locking pattern where the
-// second level of protection is a global Mutex, so if two threads attempt to
-// construct the flag concurrently only one wins.
-//
-// This solution is based on a recommendation here:
-// https://developercommunity.visualstudio.com/content/problem/336946/class-with-constexpr-constructor-not-using-static.html?childToView=648454#comment-648454
-
-namespace flags_internal {
-absl::Mutex* GetGlobalConstructionGuard();
-}  // namespace flags_internal
-
-// Public methods of `absl::Flag<T>` are NOT part of the Abseil Flags API.
-// See https://abseil.io/docs/cpp/guides/flags
-template <typename T>
-class Flag {
- public:
-  // No constructor and destructor to ensure this is an aggregate type.
-  // Visual Studio 2015 still requires the constructor for class to be
-  // constexpr initializable.
-#if _MSC_VER <= 1900
-  constexpr Flag(const char* name, const char* filename,
-                 const flags_internal::HelpGenFunc help_gen,
-                 const flags_internal::FlagDfltGenFunc default_value_gen)
-      : name_(name),
-        filename_(filename),
-        help_gen_(help_gen),
-        default_value_gen_(default_value_gen),
-        inited_(false),
-        impl_(nullptr) {}
-#endif
-
-  flags_internal::Flag<T>& GetImpl() const {
-    if (!inited_.load(std::memory_order_acquire)) {
-      absl::MutexLock l(flags_internal::GetGlobalConstructionGuard());
-
-      if (inited_.load(std::memory_order_acquire)) {
-        return *impl_;
-      }
-
-      impl_ = new flags_internal::Flag<T>(
-          name_, filename_,
-          {flags_internal::FlagHelpMsg(help_gen_),
-           flags_internal::FlagHelpKind::kGenFunc},
-          {flags_internal::FlagDefaultSrc(default_value_gen_),
-           flags_internal::FlagDefaultKind::kGenFunc});
-      inited_.store(true, std::memory_order_release);
-    }
-
-    return *impl_;
-  }
-
-  // Public methods of `absl::Flag<T>` are NOT part of the Abseil Flags API.
-  // See https://abseil.io/docs/cpp/guides/flags
-  bool IsRetired() const { return GetImpl().IsRetired(); }
-  absl::string_view Name() const { return GetImpl().Name(); }
-  std::string Help() const { return GetImpl().Help(); }
-  bool IsModified() const { return GetImpl().IsModified(); }
-  bool IsSpecifiedOnCommandLine() const {
-    return GetImpl().IsSpecifiedOnCommandLine();
-  }
-  std::string Filename() const { return GetImpl().Filename(); }
-  std::string DefaultValue() const { return GetImpl().DefaultValue(); }
-  std::string CurrentValue() const { return GetImpl().CurrentValue(); }
-  template <typename U>
-  inline bool IsOfType() const {
-    return GetImpl().template IsOfType<U>();
-  }
-  T Get() const {
-    return flags_internal::FlagImplPeer::InvokeGet<T>(GetImpl());
-  }
-  void Set(const T& v) {
-    flags_internal::FlagImplPeer::InvokeSet(GetImpl(), v);
-  }
-  void InvokeCallback() { GetImpl().InvokeCallback(); }
-
-  const CommandLineFlag& Reflect() const {
-    return flags_internal::FlagImplPeer::InvokeReflect(GetImpl());
-  }
-
-  // The data members are logically private, but they need to be public for
-  // this to be an aggregate type.
-  const char* name_;
-  const char* filename_;
-  const flags_internal::HelpGenFunc help_gen_;
-  const flags_internal::FlagDfltGenFunc default_value_gen_;
-
-  mutable std::atomic<bool> inited_;
-  mutable flags_internal::Flag<T>* impl_;
-};