Add ExitGuard.

GitOrigin-RevId: f8f04daacbee00386e326eb3ca1ec3dfec19cbb0

tdutils/CMakeLists.txt

@@ -87,6 +87,7 @@ set(TDUTILS_SOURCE
   td/utils/BufferedUdp.cpp
   td/utils/check.cpp
   td/utils/crypto.cpp
+  td/utils/ExitGuard.cpp
   td/utils/FileLog.cpp
   td/utils/filesystem.cpp
   td/utils/find_boundary.cpp
@@ -187,6 +188,7 @@ set(TDUTILS_SOURCE
   td/utils/Destructor.h
   td/utils/Enumerator.h
   td/utils/EpochBasedMemoryReclamation.h
+  td/utils/ExitGuard.h
   td/utils/FileLog.h
   td/utils/filesystem.h
   td/utils/find_boundary.h

tdutils/td/utils/ExitGuard.cpp

@@ -0,0 +1,13 @@
+//
+// Copyright Aliaksei Levin (levlam@telegram.org), Arseny Smirnov (arseny30@gmail.com) 2014-2020
+//
+// Distributed under the Boost Software License, Version 1.0. (See accompanying
+// file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
+//
+#include "td/utils/ExitGuard.h"
+
+namespace td {
+
+std::atomic<bool> ExitGuard::is_exited_{false};
+
+}  // namespace td

tdutils/td/utils/ExitGuard.h

@@ -0,0 +1,32 @@
+//
+// Copyright Aliaksei Levin (levlam@telegram.org), Arseny Smirnov (arseny30@gmail.com) 2014-2020
+//
+// Distributed under the Boost Software License, Version 1.0. (See accompanying
+// file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
+//
+#pragma once
+
+#include <atomic>
+
+namespace td {
+
+class ExitGuard {
+ public:
+  ExitGuard() = default;
+  ExitGuard(ExitGuard &&) = delete;
+  ExitGuard &operator=(ExitGuard &&) = delete;
+  ExitGuard(const ExitGuard &) = delete;
+  ExitGuard &operator=(const ExitGuard &) = delete;
+  ~ExitGuard() {
+    is_exited_.store(true, std::memory_order_relaxed);
+  }
+
+  static bool is_exited() {
+    return is_exited_.load(std::memory_order_relaxed);
+  }
+
+ private:
+  static std::atomic<bool> is_exited_;
+};
+
+}  // namespace td

tdutils/test/misc.cpp

@@ -10,6 +10,7 @@
 #include "td/utils/bits.h"
 #include "td/utils/CancellationToken.h"
 #include "td/utils/common.h"
+#include "td/utils/ExitGuard.h"
 #include "td/utils/Hash.h"
 #include "td/utils/HashMap.h"
 #include "td/utils/HashSet.h"
@@ -50,6 +51,24 @@
 
 using namespace td;
 
+struct CheckExitGuard {
+  explicit CheckExitGuard(bool expected_value): expected_value_(expected_value) {
+  }
+  CheckExitGuard(CheckExitGuard &&) = delete;
+  CheckExitGuard &operator=(CheckExitGuard &&) = delete;
+  CheckExitGuard(const CheckExitGuard &) = delete;
+  CheckExitGuard &operator=(const CheckExitGuard &) = delete;
+  ~CheckExitGuard() {
+    ASSERT_EQ(expected_value_, ExitGuard::is_exited());
+  }
+
+  bool expected_value_;
+};
+
+CheckExitGuard check_exit_guard_true{true};
+ExitGuard exit_guard;
+CheckExitGuard check_exit_guard_false{false};
+
 #if TD_LINUX || TD_DARWIN
 TEST(Misc, update_atime_saves_mtime) {
   SET_VERBOSITY_LEVEL(VERBOSITY_NAME(ERROR));