Magnus Hagander <magnus@hagander.net> writes:
> Do you still have a reference to the page that said they will never be
> assigned that high?
http://msdn.microsoft.com/en-us/library/ms810720.aspx
which says
USER and GDI handles are sign extended 32b values To facilitate the porting, a decision has been made that
thesesystem handles should stay as 32b values, sign extended to 64b on the 64b platform. That is, the individual
handletypes are still based on the HANDLE type, which maps to void *, and so the size of the handle is the size of
thepointer, i.e. 4 bytes on 32b and 8 bytes on 64b. However, the actual value of the handle on the 64b platform,
(i.e.the meaningful bits), fits within the lower 32b, while the upper bits just carry the sign. This should
makeit easy to port the majority of the application code. Handling of the special values, like -1, should be fairly
transparent.It also should agree nicely with all the cases where the handles had been remoted with the help of the
IDLdefinitions from the public file wtypes.idl. However, care needs to be taken when remoting the handles was done
viaa DWORD, as the upper long should be properly sign extended on the 64b side. The app should use HandleToLong() and
LongToHandle() macros (inline functions) to do the casting right.
What's not clear to me is whether the section title means that only
certain handles have this guarantee, and if so whether we have to worry
about running into ones that don't.
regards, tom lane
