Re: [Caml-list] Scoped Bound Resource Management just for C++?

[orbitz@ezabel.com]

Thanks for the answers everyone.

How does one safely write code in Ocaml that guarantees resources will  
be freed?  Guillaume mentioned the with-idiom, but even that doesn't  
seem entirely safe.

On Feb 9, 2011, at 7:01 AM, rossberg@mpi-sws.org wrote:

>> One of the benefits, in my opinion, of C++ is SBRM.  You can reason
>> about the lifetime of an object and have an give yourself guarantees
>> about its clean up.  The method of initialization and clean up are
>> also consistent for every object in the language.
>
> Don't believe the hype. :) Scope-bound resource management is  
> inherently
> broken, at least without sophisticated type system support. In a
> higher-order language, there are various ways in which objects could  
> escape
> their scope, e.g. closures, references, exceptions. That can only  
> mean one
> of two things for SBRM:
>
> 1) Either it is not actually true, i.e. life times are not actually  
> bound by
> scope in general and you have no actual guarantees,
>
> 2) or it is unsafe, i.e. you can access an object after its life  
> time has
> ended, with potentially desastrous effects.
>
> C++ chose (2), which is out of the question for a safe language. If  
> your
> language makes heavy use of first-class functions (and thus  
> closures) that
> strategy is a particular no-go.
>
> Also, SBRM does not scale at all to concurrency. The underlying  
> assumption
> that all life times are somehow well-bracketed through the dynamic  
> calling
> hierarchy simply doesn't hold anymore when you have shared-state
> concurrency. Getting life times right in concurrent C++ is a  
> nightmare in my
> experience, and often requires synchronizing deallocation in quite
> inefficient ways (thereby effectively making it explicit, and  
> subverting the
> whole idea of tying it to scope implicitly).
>
> /Andreas
>