ctypes.windll.kernel32.GetProcAddress returns address of 0

Hello ctypes-users,


I am a novice at ctypes and C. I am trying to get the addresses of some methods in ddraw.dll (obsolete, I know) so that I may use them with pygame. When I run the script below to get the methods' addresses, ctypes.windll.kernel32.GetProcAddress gives me addresses of 0. Can you see something that I'm doing wrong?


I have tried this in Python 2.7 (32-bit) under Win 7 (64-bit) and Python 2.5 (32-bit) under Win XP (32-bit). I got the same result in both environments.


Thanks,
Jason


# coding: cp1252
# What I am trying to do:
#   http://www.nerdblog.com/2010/04/fun-vertical-sync-hack.html
#
# DirectDrawCreate function
#   http://msdn.microsoft.com/en-us/library/windows/desktop/gg426116%28v=vs.85%29.aspx
# IDirectDraw7::GetMonitorFrequency method
#   http://msdn.microsoft.com/en-us/library/windows/desktop/gg426148%28v=vs.85%29.aspx
# IDirectDraw7::GetScanLine method
#   http://msdn.microsoft.com/en-us/library/windows/desktop/gg426149%28v=vs.85%29.aspx
# 
# DirectX headers
#   http://www.steve-oh.com/blog/index.php/directx-70a-sdk-download/
#
# scary GUID structure
#   https://code.google.com/p/pyglet/source/browse/pyglet/com.py
# scary pointer to a pointer
#   http://stackoverflow.com/questions/8638942/python-ctypes-pointer-to-pointer-to-structure

import ctypes
from ctypes import POINTER, WINFUNCTYPE, byref, c_int, c_char_p, c_void_p, windll, wintypes

DD_OK = 0

# Load DirectDraw DLL
ddraw_dll = windll.LoadLibrary("ddraw")

# Initialize DirectDraw with DirectDrawCreate
class GUID(ctypes.Structure):
    _fields_ = [
        ('Data1', ctypes.c_ulong),
        ('Data2', ctypes.c_ushort),
        ('Data3',
 ctypes.c_ushort),
        ('Data4', ctypes.c_ubyte * 8)
    ]


    def __init__(self, l=0x6C14DB80, w1=0xA733, w2=0x11CE, b1=0xA5, b2=0x21, b3=0x00, b4=0x20, b5=0xAF, b6=0x0B, b7=0xE5, b8=0x60): # IID_IDirectDraw
        self.Data1 = l
        self.Data2 = w1
        self.Data3 = w2
        self.Data4[:] = (b1, b2, b3, b4, b5, b6, b7, b8)

    def __repr__(self):
        b1, b2, b3, b4, b5, b6, b7, b8 = self.Data4
        return 'GUID(%x, %x, %x, %x, %x, %x, %x, %x, %x, %x, %x)' % (
            self.Data1, self.Data2, self.Data3, b1, b2, b3, b4, b5, b6, b7, b8)

DirectDrawCreate = ddraw_dll.DirectDrawCreate
DirectDrawCreate.argtypes = [c_void_p,
 POINTER(POINTER(GUID)), c_void_p]
control = POINTER(GUID)()
result = DirectDrawCreate(None, byref(control), None)

print "DirectDrawCreate result (0 is DD_OK):", result
assert result == DD_OK, "DirectDraw did not initialize"

# Get GetMonitorFrequency function's address
windll.kernel32.GetProcAddress.argtypes = [c_void_p, c_char_p]
GetMonitorFrequency_addr = windll.kernel32.GetProcAddress(ddraw_dll._handle, "GetMonitorFrequency")
print "GetMonitorFrequency_addr", hex(GetMonitorFrequency_addr)

# Get GetScanLine function's address
GetScanLine_addr = windll.kernel32.GetProcAddress(ddraw_dll._handle, "GetScanLine")
print "GetScanLine_addr", hex(GetScanLine_addr)

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