Question

I have the following code:

    HANDLE h = NULL;
    init(h);
    dosomething(h);

How do I set “h” in the init function in order to use it in the dosomething function?

Answer 1

You need to pass the address of h to init() as C passes by value:

void init(HANDLE* a_h)
{
    *a_h = ...; /* some handle. */
}

and invoked:

init(&h);
if (h)
{
    dosomething(h);
    CloseHandle(h);
}

In addition to passing the address of the HANDLE into init(), depending on action required in event of failure to acquire a HANDLE, you may also pass in the address of DWORD to store the last error in the event of failure to make this information available to the caller:

void init(HANDLE* a_h, DWORD* a_last_error)
{
    *a_h = /* code to acquire handle. */;
    if (NULL == *a_h) *a_last_error = GetLastError();
}