base: Fix DCHECK when thread creation fails

base/message_loop/message_loop.cc

 // Copyright 2013 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 "base/message_loop/message_loop.h"
 
 #include <algorithm>
 #include <utility>
 
 #include "base/bind.h"
@@ skipping 115 matching lines @@
     : MessageLoop(type, MessagePumpFactoryCallback()) {
   BindToCurrentThread();
 }
 
 MessageLoop::MessageLoop(scoped_ptr<MessagePump> pump)
     : MessageLoop(TYPE_CUSTOM, Bind(&ReturnPump, Passed(&pump))) {
   BindToCurrentThread();
 }
 
 MessageLoop::~MessageLoop() {
-  // current() could be NULL if this message loop is destructed before it is
-  // bound to a thread.
-  DCHECK(current() == this || !current());
+  // If |pump_| is non-null, this message loop should be the current one on this
+  // thread. Otherwise, this loop is being destructed before it was bound to a
+  // thread, so a different message loop (or no loop at all) may be current.
+  DCHECK((pump_ && current() == this) || current() != this);

[danakj, 2016/01/06 21:03:22]

This would still pass if pump_ && current() != this. I think you want

DCHECK((pump_ && current() == this) || (!pump_ && current() != this))

ya?

[Sami, 2016/01/07 10:46:10]

Ah, right you are. Fixed, thanks.

 
   // iOS just attaches to the loop, it doesn't Run it.
   // TODO(stuartmorgan): Consider wiring up a Detach().
 #if !defined(OS_IOS)
   DCHECK(!run_loop_);
 #endif
 
 #if defined(OS_WIN)
   if (in_high_res_mode_)
     Time::ActivateHighResolutionTimer(false);
@@ skipping 21 matching lines @@
 
   thread_task_runner_handle_.reset();
 
   // Tell the incoming queue that we are dying.
   incoming_task_queue_->WillDestroyCurrentMessageLoop();
   incoming_task_queue_ = NULL;
   unbound_task_runner_ = NULL;
   task_runner_ = NULL;
 
   // OK, now make it so that no one can find us.
-  lazy_tls_ptr.Pointer()->Set(NULL);
+  if (current() == this)

[danakj, 2016/01/06 21:03:22]

Yay for tests :o

[Sami, 2016/01/07 10:46:10]

They're the best.

+    lazy_tls_ptr.Pointer()->Set(nullptr);
 }
 
 // static
 MessageLoop* MessageLoop::current() {
   // TODO(darin): sadly, we cannot enable this yet since people call us even
   // when they have no intention of using us.
   // DCHECK(loop) << "Ouch, did you forget to initialize me?";
   return lazy_tls_ptr.Pointer()->Get();
 }
 
@@ skipping 563 matching lines @@
       persistent,
       mode,
       controller,
       delegate);
 }
 #endif
 
 #endif  // !defined(OS_NACL_SFI)
 
 }  // namespace base