[python-win32] About ctypes and getprocaddress

[Alejandro Bermudez Aragurz]

Hello list,

     I'm working with ctypes doing a wrapper for a DLL. I use 
LoadLibrary, FreeLibrary and GetProcAddress of windows system API 
(kernel32.dll).

    The problem is the following: Inside a DLL there are 4 function. I 
can to request its address of 3 functions without problem 
(GetProcAddress return the correct value), but the 4th function work 
sometimes. Sometime, GetProcAddress return NULL value and GetLastError 
return error code 127. But others time, return the correct address and 
GetLastError return 0 (no error ocurred). I don't change the code 
between each try. I print too the pefile exports and this function 
appers in the pe file. The DLL is always the same. The python code is 
always the same. Why don't work well GetProcAddress sometime, and other 
time work well? Here post my code test:


import ctypes
import time

import tool_pefile

#DLLs manager
funcion_open = ctypes.windll.kernel32.LoadLibraryA
funcion_close = ctypes.windll.kernel32.FreeLibrary
funcion_direccion = ctypes.windll.kernel32.GetProcAddress

#Manejo de errores
funcion_error = ctypes.windll.kernel32.GetLastError

if __name__ == '__main__':
   
   
    count = 5
    while count:
       
        #pe file
        hPE = tool_pefile.Tool()
        txt = hPE.info_txt("c:\\windows\\system32\\TrIDLib.dll")
       
        print txt
       
        #Se abre la DLL   
        dllname = 
ctypes.create_string_buffer(len("c:\\windows\\system32\\TrIDLib.dll"))
        dllname.value = "TrIDLib.dll"
        hDLL = funcion_open( dllname )
       
        error = funcion_error()
        print str(error)
       
        #name = "TrID_Analyze"
        name = "TrID_LoadDefsPack"
        print hDLL
        #time.sleep(4)
       
        funcion = ctypes.create_string_buffer(len(name))
        funcion.value = name
       
        print funcion.value
        direccion = funcion_direccion( hDLL, funcion )
        print hex(direccion)   
       
        error = funcion_error()
        print str(error)
       
        res = funcion_close( hDLL )
        print res
       
        error = funcion_error()
        print str(error)
       
        print "To sleep"
        count -= 1
        time.sleep(2)