Re: [Boost-users] revisiting casting a boost::shared_ptr to void*

Subject: Re: [Boost-users] revisiting casting a boost::shared_ptr to void*
From: Gavin Lambert (gavinl_at_[hidden])
Date: 2014-07-29 22:15:46

On 30/07/2014 14:01, Michael Powell wrote:
> Not to beat a dead horse. But here's an apt analogy: I could be wrong,
> but you are dividing by zero and not expecting a div by zero exception
> (or worse) to occur.

I don't see how that's even slightly a valid analogy.

In any case, what the OP needs to do is to characterise the lifetime of 
the raw pointer as used by the C API, and *absolutely guarantee* that 
some shared_ptr exists at least as long as that.

There are various techniques for doing this, depending on what that 
lifetime is -- for example, if it's a single-shot callback then 
Dominique's suggestion might be reasonable, if you don't mind paying an 
extra allocation/deallocation each cycle.  If it's a multi-shot callback 
then it may be better to make a connection-management object that 
registers/unregisters with the C API and then manage the lifecycle of 
*that* object appropriately.  There's many methods.

But you have to know what the C API is going to be doing with that 
pointer, or all bets are off.