Re: general purpose RAII with closures

From:
Mathias Gaunard <loufoque@gmail.com>
Newsgroups:
comp.lang.c++.moderated
Date:
Fri, 12 Sep 2008 20:15:48 CST
Message-ID:
<5537218f-ddd6-487f-b6d4-963d4d5bda49@a70g2000hsh.googlegroups.com>
On 12 sep, 12:10, JoshuaMaur...@gmail.com wrote:

Am I correct in concluding that the only way to get what I want is
decl_type and/or auto in C++0x? I suddenly like auto that much more. I
was just wondering if there was some hackery, possibly with macros, to
get what I want in C++98. I believe not. (Now, if I was willing to
accept a virtual function call and new and delete some objects for
each instance of call_on_stack_unwind_t, I could pull it off. That's
excessive, and wasteful of run time speed IMHO.)


You would only need to make the destructor virtual.

struct call_on_stack_base
{
     virtual ~call_on_stack_base() = 0;
};

template<typename T>
struct call_on_stack_unwind_t : call_on_stack_base
{
     call_on_stack_unwind_t(T t) : f(t) {}
     ~call_on_stack_unwind_t() { f(); }
     T f;
};

template<typename T>
call_on_stack_unwind_t<T>
call_on_stack_unwind(T t)
{
     return t;
}

int main()
{
     Handle* h = allocate();
     const call_on_stack_base& helper =
call_on_stack_unwind(bind(deallocate, h));
}

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