Re: [Boost-users] Casting a shared_ptr as a prototyped (void *)?

From: Richard Dingwall (rdingwall_at_[hidden])
Date: 2008-01-16 00:12:39

On Jan 16, 2008 5:22 PM, Elli Barasch <comptonsw_at_[hidden]> wrote:
>
>  Richard Dingwall wrote:
>
>  On Jan 16, 2008 1:11 PM, Elli Barasch <comptonsw_at_[hidden]> wrote:
>
>
>  I'd like to pass a shared_ptr as the entry argument to a thread function
> via pthread_create. However,
> the entry argument is prototyped as void *. I can't simply cast the
> shared pointer as a (void *). How do I go about this?
>
>  Try passing:
>
> static_cast<void *>(your_ptr.get())
>
>
> Richard
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>
>  A follow up question.  Does get() increase the reference count, or does it
> simply return the underlying pointer without doing so?  If so, I'd be
> worried that a race exists such that the object could be destroyed before
> the thread gets to run.

get() does not incremement the reference count, as it returns a raw
pointer, and there is no way of knowing how a raw pointer is being
consumed or stored.

If you the function you are passing it to retains a reference to the
pointer anywhere, there is no way this can be tracked by the
shared_ptr. Furthermore, if the shared_ptr(s) go out of scope the raw
pointer references will be left dangling.

HTH,

Richard