Calling C DLL from Visual Basic 6: Double data type not working

I'm passing a simple user-defined type (UDT) from Visual Basic 6 to a C DLL. It works fine, except for the double data type, which shows up as 0.

C DLL:

#define WIN32_LEAN_AND_MEAN

#include <windows.h>
#include <stdio.h>

typedef struct _UserDefinedType
{
    signed int      Integer;
    unsigned char   Byte;
    float           Float;
    double          Double;
} UserDefinedType;

int __stdcall Initialize ( void );
int __stdcall SetUDT ( UserDefinedType * UDT );

BOOL WINAPI DllMain ( HINSTANCE Instance, DWORD Reason, LPVOID Reserved )
{
    return TRUE;
}

int __stdcall Initialize ( void )
{
    return 1;
}

int __stdcall SetUDT ( UserDefinedType * UDT )
{
    UDT->Byte = 255;
    UDT->Double = 25;
    UDT->Float = 12345.12;
    UDT->Integer = 1;

    return 1;
}

Visual Basic 6 code:

Option Explicit

Private Type UserDefinedType
    lonInteger As Long
    bytByte As Byte
    sinFloat As Single
    dblDouble As Double
End Type

Private Declare Function Initialize Lib "C:\VBCDLL.dll" () As Long
Private Declare Function SetUDT Lib "C:\VBCDLL.dll" (ByRef UDT As UserDefinedType) As Long

Private Sub Form_Load()

    Dim lonReturn As Long, UDT As UserDefinedType

    lonReturn = SetUDT(UDT)

    Debug.Print "VBCDLL.SetUDT() = " & CStr(lonReturn)

    With UDT
        Debug.Print , "Integer:", CStr(.lonInteg开发者_高级运维er)
        Debug.Print , "Byte:", CStr(.bytByte)
        Debug.Print , "Float:", CStr(.sinFloat)
        Debug.Print , "Double:", CStr(.dblDouble)
    End With

End Sub

The output from Visual Basic:

VBCDLL.SetUDT() = 1
              Integer:      1
              Byte:         255
              Float:        12345.12
              Double:       0

As you can see, the double is appearing as 0, when it should be 25.

VB6's UDTs align doubles at addresses that are multiples of 4. Here's how to contend with that in C:

#pragma pack(push,4)
typedef struct _UserDefinedType 
{ 
    signed int      Integer; 
    unsigned char   Byte; 
    float           Float; 
    double          Double; 
} UserDefinedType;
#pragma pack(pop)