[boost] Re: free_on_error

1 May 2005

      Jason Hise wrote:
...
Does a utility like the following already exist in boost?  If so, what
is it called?  If not, is there interest in adding it?
template < typename Function >
    struct free_on_error
    {
    private:
        Function function_;
        bool reset_;
public:
        free_on_error ( Function function ) :
            function_ ( function ),
            reset_    ( true )
        {
        }
~ free_on_error (  )
        {
            if ( reset_ )
            {
                function_ (  );
            }
        }
void discard (  )
        {
            reset_ = false;
        }
    };
This would be used to make certain operations exception safe.  For
example:
A * foo (  )
{
    A * a = new A (  );
    free_on_error < BOOST_TYPEOF ( lambda::bind ( delete _1, a ) ) >
        release ( lambda::bind ( delete _1, a ) );
    a->DoSomethingThatMightThrow (  );
    release.discard (  );
    return a;
}
It sounds like you may be looking for Petru and Andrei's ScopeGuard:
http://tinyurl.com/26vzp. (BTW, has anyone noticed http://www.scopeguard.com/ ?)

It uses a neat trick to avoid specifying the return type of bind or  lambda
expressions. A version of ScopeGuard exists as an implementation detail of
multi_index. Previously, I had used a ScopeGuard in iostreams, and was planning
to move it to boost/detail. Unfortunately it caused problems with borland 5.x,
Metrowerks 8.3 and VC6, so I excised it.

Jonathan

[boost] Re: free_on_error

Jonathan Turkanis