On Windows, set current thread in TLS to NULL before deleting the thread.

runtime/vm/thread.cc

 // Copyright (c) 2015, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 #include "vm/thread.h"
 
 #include "vm/growable_array.h"
 #include "vm/isolate.h"
 #include "vm/lockers.h"
 #include "vm/object.h"
@@ skipping 75 matching lines @@
     // Verify that current thread was set.
     ASSERT(Thread::Current() == thread);
   }
 }
 
 
 #if defined(TARGET_OS_WINDOWS)
 void Thread::CleanUp() {
   Thread* current = Current();
   if (current != NULL) {
+    SetCurrent(NULL);
     delete current;

[Ivan Posva, 2015/08/21 03:23:56]

Are we sure the destructor will not touch anything that tries to reference
Thread::Current()?

[koda, 2015/08/21 17:15:42]

I can't guarantee it won't, but if it did, we'd already have a problem with
pthreads on Linux and Mac. This CL just makes Windows consistent with their
behavior.

It's fine for the destructor to call Thread::Current as long as it guards
against null. The same is true for any initialization code that might run before
Thread::EnsureInit.

   }
-  SetCurrent(NULL);
 }
 #endif
 
 
 Thread::Thread(bool init_vm_constants)
     : id_(OSThread::GetCurrentThreadId()),
       isolate_(NULL),
       store_buffer_block_(NULL) {
   ClearState();
 #define DEFAULT_INIT(type_name, member_name, init_expr, default_init_value)    \
@@ skipping 208 matching lines @@
 #define COMPUTE_OFFSET(type_name, member_name, expr, default_init_value)       \
   ASSERT((expr)->IsVMHeapObject());                                            \
   if (object.raw() == expr) return Thread::member_name##offset();
 CACHED_VM_OBJECTS_LIST(COMPUTE_OFFSET)
 #undef COMPUTE_OFFSET
   UNREACHABLE();
   return -1;
 }
 
 }  // namespace dart