WTF: Initialize main-thread stack estimates when WTF starts up.

third_party/WebKit/Source/wtf/Threading.h

 /*
  * Copyright (C) 2007, 2008, 2010 Apple Inc. All rights reserved.
  * Copyright (C) 2007 Justin Haygood (jhaygood@reaktix.com)
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  *
  * 1.  Redistributions of source code must retain the above copyright
  *     notice, this list of conditions and the following disclaimer.
@@ skipping 29 matching lines @@
 #if OS(WIN)
 typedef uint32_t ThreadIdentifier;
 #else
 typedef intptr_t ThreadIdentifier;
 #endif
 
 namespace internal {
 WTF_EXPORT ThreadIdentifier currentThreadSyscall();
 }  // namespace internal
 
+// Must be called before |currentThread|.

[haraken, 2017/03/06 01:44:03]

Can we add a dcheck about this fact?

BTW, who calls initializeCurrentThread on non-main threads?

[jbroman, 2017/03/06 16:14:03]

Sure.
Nobody. This just does the one-time initialization needed: a pthread_key_t (or
its Windows equivalent) needs to be created before thread-local lookups can be
done, so it just needs to be done on some thread once before currentThread is
called. currentThread could do this internally (and create the key on first use,
assuming that it will be before a thread race exists), but this seems clearer
and has fewer branches in the hot path.

+WTF_EXPORT void initializeCurrentThread();
+
 WTF_EXPORT ThreadIdentifier currentThread();
 
 #if DCHECK_IS_ON()
 WTF_EXPORT bool isBeforeThreadCreated();
 WTF_EXPORT void willCreateThread();
 #endif
 
 }  // namespace WTF
 
 using WTF::ThreadIdentifier;
 using WTF::currentThread;
 
 #endif  // Threading_h