How to use C++ standard smart pointers with Windows HANDLEs?

Question

I was wondering if there is a way to use unique_ptr with Windows HANDLEs?

I was thinking to replace the std::default_delete with s

Answer 1

You can typedef your unique_ptr with a custom deleter

struct handle_deleter
{
    void operator()(void* handle)
    {
        if(handle != nullptr)
            CloseHandle(handle);
    }
};

typedef std::unique_ptr<void, handle_deleter> UniqueHandle_t;
UniqueHandle_t ptr(CreateFile(...));

Answer 2

yet another solution

std::unique_ptr< void, void(*)( HANDLE ) > uniqueHandle( file, []( HANDLE h ) { ::CloseHandle( h ); } );

Answer 3

I don't recommend using smart pointers with handles.

I recommend you to take a look at A Proposal to Add additional RAII Wrappers to the Standard Library and at the drawbacks of using smart pointers with handles.

Personally, I'm making use of the reference implementation of that proposal instead of using std::unique_ptr for these situations.

Answer 4

Create a specific smart pointer class, won't take long. Don't abuse library classes. Handle semantics is quite different from that of a C++ pointer; for one thing, dereferencing a HANDLE makes no sense.

One more reason to use a custom smart handle class - NULL does not always mean an empty handle. Sometimes it's INVALID_HANDLE_VALUE, which is not the same (actually -1).