I've been able to design a front-end for a C DLL, calling the DLL functions from the VB program but I'm having trouble calling the VB functions from the C DLL. Maybe I should have put this in the C forum, but I don't know.
If I have this in a VB module:
Public Declare Function callback Lib "C:\c\dll\mydll" (ByVal cbAddress As Long)
Public Sub cb()
MsgBox "Called back."
End Sub
and
callback AddressOf cb is used for the even of a button click or something. In a C DLL I would use this:
EXPORT void __stdcall callback(long cbAddress){
typedef void (__stdcall *funcp)();
funcp VBCallback;
VBCallback = (funcp)cbAddress;
VBCallback();
}
Well, the DLL compiles, and the VB program runs, but when I try to call the callback function, it says bad DLL calling convention. I tried taking the address by pointer as well (since I was able to pass values by pointer in the past, I figured it would work this time also) to no avail. And I commented out all the code in the function to see if that was the problem, but it wasn't--it's the VB program calling the callback function, which is using a "bad convention." The only difference I can see between the working code and the broken code, is that I'm using a Long data type, and that I'm not returning a value (which shouldn't matter...right?)
I used DUMPBIN /EXPORTS to check the exports of the DLL and I get:
1 0 00001190 callback
2 1 00001190 callback@4
I checked the data types for VB6 and it says a long is 4 bytes, and if I compile the DLL using int, long, or short the DLL export always asks for 4 bytes in parameters, so I don't know what I'm doing wrong... Any ideas? Maybe I'll link to this in the C forum as well
Marked Solved 
