Re: callback from C DLL returning an int [SEC=PERSONAL]

At 10:44 PM 7/14/2011, you wrote:

>If the callback genuinely is a C void function, then I'd have to say 
>that the library that calls it expects it to do something which your 
>code isn't doing - such as copying data out of a buffer and then 
>clearing the buffer - and the library code is subsequently blowing 
>up as a result of what ever needs doing having not been done (or 
>been signalled to have been done).  Do you have examples of 
>callbacks in other languages?
>
>Another possibility could be the calling convention used for the 
>callback function itself (as distinct from the convention used for 
>the function that sets the callback).  You really need the C++ 
>header file for the DLL to evaluate this (I'm assuming C++ based on 
>the snippets posted in your original message).


I just heard from the DLL author that (FUNCPTR) in the callback 
declaration is actually a macro for the following function typedef:
         typedef void (__stdcall *FUNCPTR)( int iStatus );

This is the c code:
         extern "C" void __declspec(dllexport) SetCallback( long lAddress )   {
             s_frontend.set_callback((FUNCPTR)lAddress );
         }

This is the .h declaration:
         extern "C" void __declspec(dllexport) SetCallback(long lAddress);

This is my Python call:
def py_data_ready_func(r):
     print "in py_data_ready_func 1", r

driver = ctypes.cdll.VBridge
CB_TYPE = ctypes.CFUNCTYPE(None, ctypes.c_int)
data_ready_ref = CB_TYPE(py_data_ready_func)
driver.SetCallback(data_ready_ref)

The FUNCPTR macro specifies __stdcall (?), but, if I use 
windll.VBridge to load the DLL none of the other methods will load - 
"ValueError: Procedure probably called with too many arguments (4 
bytes in excess)".
It is still beyond me where the issue lies, do they have a conflict 
in their declarations?

Ray

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