Re: INVALID_HANDLE_VALUE vs. NULL

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On 5/17/05 11:20 AM, in article #62X22wWFHA.3676@xxxxxxxxxxxxxxxxxxxx, "Gary
Chanson" <gchanson@xxxxxxxxxxxxxxxxxxxx> wrote:

>> The INVALID_HANDLE_VALUE, which is -1, is in fact a valid handle, which
>> means "this process". Of course, ReadFile() will fail with this handle,
>> because the object type is wrong, just like ReadFile() will fail on a
>> perfectly valid handle of a mutex, a thread, etc.
>
> Then why did they make INVALID_HANDLE_VALUE -1?

I believe this page has been linked at least twice so far in this thread,
but another link can't hurt (especially since this is not the only reason I
am posting yet again):

http://blogs.msdn.com/oldnewthing/archive/2004/03/02/82639.aspx

>> CloseHandle() does indeed fail when given a bad handle. It will fail on
>> both -1 and 0: -1 cannot be closed, and 0 is just wrong. When CloseHandle()
>> fails, it checks whether a debugger is attached to the process, in which
>> case it raises an exception.
>
> When I try it, I don't see an exception for either -1 or 0.

I haven't been able to make the exception happen either. I may not be
running an appropriate flavor of debugger. However, CloseHandle does fail
when passed 0 and a subsequent call to GetLastError does return
ERROR_INVALID_HANDLE.

.

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