[boost] free_on_error

1 May 2005

      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;
}

(my experience with lambda is minimal, so I'm not sure that delete _1 
creates a valid lambda functor, but you get the idea)

-Jason

[boost] free_on_error

Jason Hise