I've got a Managed C++ class that's being called from C#, and the C# code
needs to look like this :

byte * p = myManagedCppClassInstance.AllocateDmaBuffer(1000) ;
// Do various things, then ...
myManagedCppClassInstance.FreeDmaBuffer(ref p) ;
// The 'free' routine has set 'p' to zero

The problem is with the declaration of 'FreeDmaBuffer' in the Managed C++
class. In an attempt to make the pointer appear as a 'ref' variable, I've
tried the following :

void FreeDmaBuffer ( unsigned char * & p )
{
 // Free the resource, then ...
 p = 0 ;
}

and also

void FreeDmaBuffer (
 [System::Runtime::InteropServices::InAttribute]
 [System::Runtime::InteropServices::OutAttribute]
 unsigned char * p // Also tried & p here ...
) {
 p = 0 ;
}

But in all cases, the C# compiler complains about a type mismatch.

I'm sure this must be possible - does anyone know how ?

Thanks,

Steve.