Eryk Sun <[email protected]> added the comment:
The default function result type is c_int, which truncates a 64-bit pointer to
32-bit. The attribute that needs to be set is singular restype, not plural
restypes. Unfortunately ctypes objects have a dict, so you're not catching the
typo in an obvious way.
Additional comments:
POINTER(c_ubyte).from_address(ptr) is not the same as cast(ptr,
POINTER(c_ubyte)). The first one wrongly instantiates a pointer from the value
at the ptr address instead of the address itself. If you want to use
from_address, where ptr is a Python integer, a correct expression for this is
POINTER(c_ubyte)(c_ubyte.from_address(ptr)).
I recommend using kernel32 = WinDLL('kernel32', use_last_error=True) instead of
windll. This allows using ctypes.get_last_error() instead of
kernel32.GetLastError(), which is especially more reliable when working in the
REPL. It also avoids the problem with cached libraries on the global windll
object, which can lead to prototype conflicts between libraries (e.g. if a
script makes use of your library and another that uses the Windows API via
ctypes, such as colorama), since libraries in turn cache function pointers.
----------
nosy: +eryksun
resolution: -> not a bug
stage: -> resolved
status: open -> closed
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Python tracker <[email protected]>
<https://bugs.python.org/issue35326>
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