Confused about a thread-safe singleton example.

From:
"jason.cipriani@gmail.com" <jason.cipriani@gmail.com>
Newsgroups:
comp.lang.c++
Date:
Tue, 2 Dec 2008 16:25:14 -0800 (PST)
Message-ID:
<962e1281-0dd3-4571-b941-1de092ff63ed@j32g2000yqn.googlegroups.com>
I have a C++-specific question about thread-safe singleton instances.
There's a trivial example here:

http://www.bombaydigital.com/arenared/2005/10/25/1

That goes like this, very simple and straightforward:

static Mutex mutex;
static TheClass *instance;

static TheClass * getInstance () {
   MutexLocker lock(mutex);
   if (!instance)
     instance = new TheClass();
   return instance;
}

The example then goes on to talk about how double-check locking is
broken, etc. My question is pretty much this: Is C++ static
initialization thread-safe? If not, then how does the above example
safely use "mutex"? If so, then what is wrong with this:

static TheClass instance; // not a pointer

static TheClass * getInstance () {
  return &instance; // it's correctly initialized?
}

The reason I ask is I almost never see it done like that, I always see
blog entries and articles that say the same thing "store instance in a
pointer, use a mutex to protect, and p.s. double-checked locking is
broken". It seems like doing it lock-free is made out to be a hard
problem, so *if* having a static instance works (but I don't know if
it does, that's my question), then why doesn't anybody ever suggest
it?

Thanks!
Jason

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