Re: [boost] Proposed new RAII Library

Subject: Re: [boost] Proposed new RAII Library
From: Vicente J. Botet Escriba (vicente.botet_at_[hidden])
Date: 2012-09-14 16:52:31

Le 14/09/12 21:12, Sohail Somani a écrit :
> On 14/09/2012 2:58 PM, Andrew Sandoval wrote:
>> True, but that is why I was proposing two RAII classes.  One that is 
>> limited and
>> uses only static values for the deleter function and the no-delete 
>> value, and
>> another that is much more open including state (RAIIFunction) because 
>> you can
>> use bind with it, and lambda's that provide any needed state.
>
> Ok, I guess you like the one with it encoded in the type. I can see 
> its value.
>
> Regarding the second kind:
>
> https://github.com/ryppl/boost-svn/blob/master/boost/scope_exit.hpp#L615
>
> Yes, it's already there but hidden in aux or detali or something.
>
> operator= is a more general dismiss().
>
> So just making it public would be great.
I don't like that the destructor checks for f_ in the preceding link.

template<>
struct guard<void> { ~guard() { if(f_) f_(); }
template<typename Lambda>
void operator=(Lambda f) { f_ = f; }
private:
boost::function<void (void)> f_;
};

And I don't know if the assignment operator should be exposed to the 
user, even if it could have no cost. Anyway the current implementation 
could require that the parameter should be Callable. The null pattern 
should be applied there and assigning a lambda that do nothing will 
avoid the check.

BTW, couldn't the cost of boost::function be reduced using the reference 
to a base class technique used in multi_index/detail/scope_guard.hpp and 
described in
  Alexandrescu, A., Marginean, P.:"Generic<Programming>: Change the Way 
You Write Exception-Safe Code - Forever", C/C++ Users Jornal, Dec 2000,
http://www.drdobbs.com/184403758

Best,
Vicente