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

This solution is based on Nicol Bolas answer:

struct FdDeleter
{
    typedef int pointer;
    void operator()(int fd)
    {
        ::close(fd);
    }
};
typedef std::unique_ptr UniqueFd;

It's short, but you have to avoid to compare UniqueFd instance with nullptr and use it as boolean expression:

UniqueFd fd(-1, FdDeleter()); //correct
//UniqueFd fd(nullptr, FdDeleter()); //compiler error
if (fd.get() != -1) //correct
{
    std::cout << "Ok: it is not printed" << std::endl;
}
if (fd) //incorrect, avoid
{
    std::cout << "Problem: it is printed" << std::endl;
}
if (fd != nullptr) //incorrect, avoid
{
    std::cout << "Problem: it is printed" << std::endl;
}
return 1;