Using unique_ptr to control a file descriptor

Question

In theory, I should be able to use a custom pointer type and deleter in order to have unique_ptr manage an object that is not a pointer. I tried the following c

Answer 1

I would suggest using shared_ptr rather than unique_ptr to manage the life time of int handles because the shared ownership semantics are usually a better fit, and because the type of the deleter is erased. You need the following helper:

namespace handle_detail
{
    template 
    struct deleter
    {
        deleter( H h, D d ): h_(h), d_(d) { }
        void operator()( H * h ) { (void) d_(h_); }
        H h_;
        D d_;
    };
}

template 
std::shared_ptr
make_handle( H h, D d )
{
    std::shared_ptr p((H *)0,handle_detail::deleter(h,d));
    return std::shared_ptr(
        p,
        &std::get_deleter >(p)->h_ );
}

To use with a file descriptor:

int fh = open("readme.txt", O_RDONLY); // Check for errors though.
std::shared_ptr f = make_handle(fh, &close);