text: // Copyright (c) 2011 The Chromium Authors. All rights reserved.
  // Use of this source code is governed by a BSD-style license that can be
  // found in the LICENSE file.
  
  #include "butil/at_exit.h"
  
  #include <stddef.h>
  #include <ostream>
  
  #include "butil/bind.h"
  #include "butil/callback.h"
  #include "butil/logging.h"
  
  namespace butil {
  
  // Keep a stack of registered AtExitManagers.  We always operate on the most
  // recent, and we should never have more than one outside of testing (for a
  // statically linked version of this library).  Testing may use the shadow
  // version of the constructor, and if we are building a dynamic library we may
  // end up with multiple AtExitManagers on the same process.  We don't protect
  // this for thread-safe access, since it will only be modified in testing.
  static AtExitManager* g_top_manager = NULL;
  
  AtExitManager::AtExitManager() : next_manager_(g_top_manager) {
  // If multiple modules instantiate AtExitManagers they'll end up living in this
  // module... they have to coexist.
  #if !defined(COMPONENT_BUILD)
    DCHECK(!g_top_manager);
  #endif
    g_top_manager = this;
  }
  
  AtExitManager::~AtExitManager() {
    if (!g_top_manager) {
      NOTREACHED() << "Tried to ~AtExitManager without an AtExitManager";
      return;
    }
    DCHECK_EQ(this, g_top_manager);
  
    ProcessCallbacksNow();
    g_top_manager = next_manager_;
  }
  
  // static
  void AtExitManager::RegisterCallback(AtExitCallbackType func, void* param) {
    DCHECK(func);
    RegisterTask(butil::Bind(func, param));
  }
  
  // static
  void AtExitManager::RegisterTask(butil::Closure task) {
    if (!g_top_manager) {
      NOTREACHED() << "Tried to RegisterCallback without an AtExitManager";
      return;
    }
  
    AutoLock lock(g_top_manager->lock_);
    g_top_manager->stack_.push(task);
  }
  
  // static
  void AtExitManager::ProcessCallbacksNow() {
    if (!g_top_manager) {
      NOTREACHED() << "Tried to ProcessCallbacksNow without an AtExitManager";
      return;
    }
  
    AutoLock lock(g_top_manager->lock_);
  
    while (!g_top_manager->stack_.empty()) {
      butil::Closure task = g_top_manager->stack_.top();
      task.Run();
      g_top_manager->stack_.pop();
    }
  }
  
  AtExitManager::AtExitManager(bool shadow) : next_manager_(g_top_manager) {
    DCHECK(shadow || !g_top_manager);
    g_top_manager = this;
  }
  
  }  // namespace butil
  