Improve log guard.

tdutils/td/utils/AsyncFileLog.cpp

@@ -61,8 +61,7 @@ Status AsyncFileLog::init(string path, int64 rotate_threshold, bool redirect_std
           }
           while (!slice.empty()) {
             if (redirect_stderr) {
-              auto &guard = get_log_guard();
-              while (guard.load() != 0) {
+              while (has_log_guard()) {
                 // spin
               }
             }

tdutils/td/utils/FileLog.cpp

@@ -83,8 +83,7 @@ void FileLog::do_append(int log_level, CSlice slice) {
   }
   while (!slice.empty()) {
     if (redirect_stderr_) {
-      auto &guard = get_log_guard();
-      while (guard.load() != 0) {
+      while (has_log_guard()) {
         // spin
       }
     }

tdutils/td/utils/logging.cpp

@@ -250,9 +250,24 @@ void process_fatal_error(CSlice message) {
   std::abort();
 }
 
-std::atomic<uint32> &get_log_guard() {
-  static std::atomic<uint32> log_guard;
-  return log_guard;
+static std::atomic<uint32> log_guard;
+
+LogGuard::LogGuard() {
+  uint32 expected = 0;
+  while (!log_guard.compare_exchange_strong(expected, 1, std::memory_order_relaxed, std::memory_order_relaxed)) {
+    // spin
+    CHECK(expected == 1);
+    expected = 0;
+  }
+}
+
+LogGuard::~LogGuard() {
+  CHECK(log_guard.load(std::memory_order_relaxed) == 1);
+  log_guard.store(0, std::memory_order_relaxed);
+}
+
+bool has_log_guard() {
+  return log_guard.load(std::memory_order_relaxed) == 1;
 }
 
 namespace {

tdutils/td/utils/logging.h

@@ -221,7 +221,17 @@ class Logger {
   int log_level_;
 };
 
-std::atomic<uint32> &get_log_guard();
+class LogGuard {
+ public:
+  LogGuard();
+  LogGuard(const LogGuard &) = delete;
+  LogGuard &operator=(const LogGuard &) = delete;
+  LogGuard(LogGuard &&) = delete;
+  LogGuard &operator=(LogGuard &&) = delete;
+  ~LogGuard();
+};
+
+bool has_log_guard();
 
 class ScopedDisableLog {
  public: