How Can I Define C functions to use VB Callback

[Ceri]

How do i define functions in C so that vb is able to pass through a function address (using the AddressOf function in VB6) adn then what whould be the code in C to call that function address

thanks in advance

[CornedBee]

a VB funciton that should be called must be declared in the main module:

public function MyCallback(i as Long, j as Long) as Long

can be passed to a function in C as follows:

// define the type of the function
typedef long (__stdcall* VBCB)(long, long);

// then the function that receives the address:
void __stdcall Func(long i, VBCB pVbFunc)
{
  // call the function
  long j = pVbFunc(i, i+1);
} 

and the remaining Vb code:

private declare sub Func lib "thedll" (i as long, pFunc as long)

'call it
Func 34 AddressOf(MyCallback)
'maybe you need to add "" to the function name

[CornedBee]

MISTAKE!!!

public function MyCallback(i as Long, j as Long) as Long
'needs to be
public function MyCallback(byval i as Long, byval j as Long) as Long

or you end up with vb.exe producing an access violation

private declare sub Func lib "thedll" (i as long, pFunc as long)
'needs to be
private declare sub Func lib "thedll" (byval i as long, byval pFunc as long)

[Ceri]

Thanks for that. It works great