[foreign] Handling pointers with special (negative) values

[Jorn Vernee]

Hello,

I was in the process of adding a windows equivalent for the getpid test. 
The windows equivalent calls GetCurrentProcess [1] to get a handle to 
the current process, and then calls GetProcessId [2] using that handle. 
The problem is that the returned handle for the current process has a 
special value, which after converting to a Java long shows up as -1. 
It's type is `void *` ([3] see `HANDLE`).

The constructor of BoundedMemoryRegion checks to make sure that the base 
(i.e. `min`) is not smaller than 0, but in this case it is, so an IAE is 
thrown [4].

I have simply removed the check on `min` and all tests that I'm running 
currently are still passing, but I don't think this is a definitive 
solution. I wanted to bring this up to discuss how we should handle 
pointers with special (negative) values, or pointers that otherwise end 
up negative after converting to a Java long. Perhaps there was some 
earlier discussion about this that I missed?

Jorn

[1] : 
https://docs.microsoft.com/en-us/windows/desktop/api/processthreadsapi/nf-processthreadsapi-getcurrentprocess
[2] : 
https://docs.microsoft.com/en-us/windows/desktop/api/processthreadsapi/nf-processthreadsapi-getprocessid
[3] : 
https://docs.microsoft.com/en-us/windows/desktop/winprog/windows-data-types
[4] : 
http://hg.openjdk.java.net/panama/dev/file/4b634b7d0cdb/src/java.base/share/classes/jdk/internal/foreign/memory/BoundedMemoryRegion.java#l74