This entry is basically my memorandum so that I won't make mistake.
HANDLE for a process, as a type, cannot be represented by an int.
As long as the value of HANDLE is small (fits in 32-bit), it works.
In the long run, it's better to have API, with something like gpgrt_process_t,
where gpgrt_process_t can represent HANDLE as a type.
pid_t of getpid and process HANDLE is different thing.