AccessViolationException when trying to call c# callback - c++

Question

I have this simple code:
typedef void (__stdcall * OrdersCallback)(ordersTest*);
__declspec(dllexport) void InitializeCallbacks(long ordersCallbackAddress_) {
OrdersCallback ordersCallbackFunction;
std::cout << "current ordersCallbackFunction = " << ordersCallbackFunction << " address = " << &ordersCallbackFunction << std::endl;
std::cout << "set ordersCallbackAddress_ = " << ordersCallbackAddress_ << std::endl;
ordersCallbackFunction = (OrdersCallback) ordersCallbackAddress_;
std::cout << "new ordersCallbackFunction = " << ordersCallbackFunction << " address = " << &ordersCallbackFunction << std::endl;
ordersTest test;
test.replID = 123;
std::cout << "use ordersCallbackFunction = " << ordersCallbackFunction << " address = " << &ordersCallbackFunction << std::endl;
ordersCallbackFunction(&test);
}
And when callback is calling AccessViolationException is raised:
current ordersCallbackFunction = 000007F92BC354E0 address = 0000009785D1EC68
set ordersCallbackAddress_ = -2043003524
new ordersCallbackFunction = FFFFFFFF863A3D7C address = 0000009785D1EC68
use ordersCallbackFunction = FFFFFFFF863A3D7C address = 0000009785D1EC68
Unhandled Exception: System.AccessViolationException: Attempted to read or write protected memory. This is often an indication that other memory is corrupt.
I can't understand what's wrong, in another project very similar code works. Thanks!
upd, more code:
[UnmanagedFunctionPointer(CallingConvention.StdCall)]
public delegate void OrdersCallback(ref OrdersTest value);
[DllImport("CGateNativeAdapter.dll"), SuppressUnmanagedCodeSecurity]
public static extern void InitializeCallbacks(
[MarshalAs(UnmanagedType.FunctionPtr)] OrdersCallback ordersSnapshotCallbackPointer);
OrdersCallback ordersCallback =
delegate(ref OrdersTest value)
{
Console.WriteLine("C# Orders call received = " +
" replID = " + value.replID);
};
InitializeCallbacks(ordersCallback);

Answer 1

The most obvious flaw in what you have shown is that you are attempting to pass the 64 bit pointer as 32 bit value which clearly cannot work. The ordersCallbackAddress_ parameter is declared as long, which is 32 bits wide. But you clearly have a 64 bit process. That almost certainly explains the error that your are experiencing.
Remember that in C++ on Windows, long is 32 bits wide. In C# it is 64 bits wide. In any case you should not use integral types to pass pointers. If you have a pointer, design your functions to operate on pointers.
You need to make sure that ordersCallbackAddress_ is declared to be pointer sized. I don't understand why it is not declared as OrdersCallback.
There may be other problems, but you did not show very much code. You did not show struct declarations, or anything on the managed side of the interface.