Re: why boost:shared_ptr so slower?

James Kanze <>
Sat, 22 Aug 2009 03:48:49 -0700 (PDT)
On Aug 21, 4:37 pm, Juha Nieminen <nos...@thanks.invalid> wrote:

Chris M. Thomasson wrote:

FWIW, Boost shared_ptr only provides basic/normal
thread-safety. It does NOT provide strong thread-safety in
any way shape or form.

I don't even understand the difference between "basic/normal"
and "strong".

"basic/normal" thread-safety is what is normally meant by thread
safety (e.g. Posix guarantees). "Strong" thread safety is
something more: it means that the object state can be modified
(from the client point of view) from several threads
simultaneously. It can be useful in a few specific cases
(message queues, etc.), but is expensive, and not generally
useful enough to warrant the expense.

As you might imagine, when used without further qualification,
"thread-safety" means normal thread-safety.

boost::shared_ptr is thread-safe because instance of it can be
used in different threads even if these instances point to the
same object. boost::shared_ptr doesn't malfunction if two
threads manipulate these instances at the same time.

Exactly. Also, you can use the same instance in many threads
provided no thread mutates it (again, from a client point of

James Kanze (GABI Software)
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