如何将结构的结构包含数组从vba传递到c-dll

Question

I am trying to pass a rather large struct, containg several nested structs, to a c-dll via vba.

I can do this just fine as long as there are no nested structs. However, introducing the arrays of additional structs into the main struct is not working. I use visual studio 2015 and I have used "attach to process" to see what is going on inside the dll. The first five variables in WL400PoliseRiskInn (the main struct) are passed just fine, but inside the array "dekninger" something goes bad.

Everything down to, and including, "antallDekninger" is correct, but as soon as we look into the nested types, things are not as they should be. The variable "alder" has the value that should be contained in "riskOpphoerAlder", and everything else seem to be out of sync. "rider" should be 1 and "crtable" should be "DS30". I assume there some sort of offset once we step into the array.

I have checked and double checked that my type definitions in vba match my c-structs, and as far as i can tell, they do. Am I missing something here? Do i have to do something magical in my array declarations in VBA. I really don't want to tamper with my c-declarations as they are used in the c-dll, and i dont want to write another c-struct and copy from that one (reuse and all that..)

My vba definitions are like this

Type WL400Lext
    lextno As Long
    prosentTillegg As Long
    promilleTillegg As Long
    risikosum As Long
    datoOpphoer As String * 11
End Type

Type WL400DekningRiskInn
    rider As Long
    crtable As String * 5
    kjoenn As Byte
    alder As Long
    riskOpphoerAlder As Long
    sumins As Long
    royker As Byte
    karens As Long
    yrkesfaktor As Double
    antallLext As Long
    L400Lext(0 To 4) As WL400Lext
End Type

Type WL400PoliseRiskInn
    chdrnum As Long
    cnttype As String * 4
    datoBeregning As String * 11
    datoTegning As String * 11
    antallDekninger As Long
    dekninger(0 To 12) As WL400DekningRiskInn
    wrapstatus As Long
 End Type

And in the recieving end I have the corresponding c-types

 typedef struct
 {
     int lextNo;
     int prosentTillegg;
     int promilleTillegg;
     int risikosum;
     char datoOpphoer[11];
 } WL400Lext;

 typedef struct
 {
     int rider;
     char crtable[5];
     char kjoenn;
     int alder;
     int riskOpphoerAlder
     int sumins;
     char royker;
     int karens;
     double yrkesfaktor;
     int iAntallLext;
     WL400Lext l400Lext[5];
} WL400DekningRiskInn;

typedef struct
{
    int chdrnum;
    char cnttype[4];
    char datoBeregning[11];
    char datoTegning[11];
    int antallDekninger;
    WL400DekningRiskInn dekninger[13];
    int wrapstatus;
} WL400PoliseRiskInn;

The calling code in vba looks like this

Public Declare Function dllBerL400PoliseRisk Lib "WinL400DLL" (polise As WL400PoliseRiskInn) As Long

Function berPoliseRisk(rngPolise As Range, rngDekninger As Range, rngLext As Range) As Long

    //lots of stuff here to fill the struct

    //Call the dll by reference   
    dllBerL400PoliseRisk polise

    //Return dummy for now whilst sorting things out :|
    berPoliseRisk = 3

End Function

I assign to the single byte values like so

Dim kjoenn as String
dekning.kjoenn = Asc(kjoenn)

And the strings like so

Dim crtable as String
dekning.crtable = crtable & Chr(0)

Where crtable is of length 4 (5 total with Chr(0))

And the corresponding code in c is

__declspec(dllexport) int _stdcall dllBerL400PoliseRisk(WL400PoliseRiskInn *wL400PoliseRiskInn)
{
    //Do stuff
}

Answer 1

A colleague and I looked a bit more into it and it turns out this is already answered in this thread Accessing a nested structure in C++ from VBA . Argut's answer solved it!

That is... the trick is to introduce

#pragma pack(4)

//All the c declarations

#pragma pack()

in the header file declaring the c-structs