windll ctypes从python 2.7调用可变参数c函数在win64中起作用，但在win32中不起作用

Question

I'm using Python 2.7 on Windows 10-32 and Windows 10-64.

I'm writing a python wrapper to a C compiled stdcall (Windows) DLL (= mydll). I have 2 versions of the DLL - 32 and 64 bit. The 64 version works great using windll.mydll . The 32 version works great using the same command for all functions on the DLL, except for variadic printf -like functions.

When running mydll.myvarfunc("Hello")

I get ValueError: Procedure probably called with too many arguments (4 bytes in excess)

Is there a way around this that does not involve changing the C code for the variadic functions?

Answer 1

On Win64, there is only one ABI so WinDLL and CDLL make no difference. On Win32, variadic functions are always __cdecl so WinDLL is using the wrong calling convention.

One way to work around this:

import ctypes
stdcall_func = ctypes.WinDLL('mydll').stdcall_func
cdecl_func = ctypes.CDLL('mydll').cdecl_func