bad dll calling convention

[ejudy]

here is C function:

int Dosth (char inflag)

here is calling from VB:

public declare function Dosth lib "**.dll" (byval flag as byte) as long

dim a as byte
dim ret as long
ret=Dosth(a)

when I call Dosth, got "bad dll calling convention"..... is it because the dll itself(it is now a try version dll) or my vb code?

Thanks if you can answer.

[parksie]

int WINAPI Dosth (char inflag)

Try that. You'll need to #include <windows.h> for that to work though (what compiler are you on? If it's MSVC, use __stdcall and don't bother including the header).

Then, you need a .def file to define the names for the functions.

I posted a tutorial on the forum somewhere, search for "export" under my name.

[ejudy]

Thanks, parksie.

Now I can call function in the dll. Here is another question : how can i trace and debug the function in dll when I call them using vb? I just want to know if the correct value is paased to the C function.....any suggestion?


Tnx lot.

[parksie]

That depends very significantly on your debugger...I'm not sure whether there's any easy way to debug a VB program into the DLL...you might be able to do it with some serious messing with the VC++ debugger but I wouldn't be able to describe it

[ejudy]

I know, it is not so easy. Right now, I just add code to write some data to file to check the procudure. (maybe not a good way, but I can get some feedback).

Now I met another interesting question. I was struggling all day but coundn't figure out. Maybe some of you had experience before. I would greatly appreciate if you'd like to have a look and give your conments.

Here is code in C++(Dll):

typedef struct _user {
    ULONG      ID;
    char  name[64];
} User;
typedef struct _userList {
    ULONG  count;
    User      users[1];
} UserList


 DWORD  m_numUsers;
 User       m_users[100];

int GetUsers( UserList *outList )
{
    User  *ptr = &outList->users[0];
    outList->count = m_numUsers;
    for( int i = 0; i < (int)m_numUsers; i++ ) {
        memcpy( ptr, &m_users[i], sizeof(User) );
        ptr++;
    }
    return 0;
}

Here is VB code

Public Type User
    ID         As    long
    Name    As   String * 64              
End Type
Public Type UserList
    Count     As  Long       
    Users()   As  User
End Type
Public Declare Function GetUsers Lib "user.dll" _
    (ByRef uList As UserList) As long

private sub cmd_click()
     Dim uList As UserList
     lRet = GetUsers(uList)//memory can't be read..... 
     lCount = uList.Count
End sub

P.S.
oh, I didn't expected to get a such a quick answer. I just made misoperation when I trying to edit my code.(sorry about that).

[parksie]

Please, please, please use [ code ] [ /code ] tags! It makes it almost unreadable with all the spacing gone, since that's the best way of finding the scope of things.

It's very difficult to understand a long piece of code in a browser window with all the spacing gone!

The problems you're running into here are more likely to be structure padding related, which I can't help with since I haven't used VB for a VERY long time, and can't remember exactly how it does it. Either way, you can't make any assumptions about how they're stored internally.

[CornedBee]

I somehow managed to jump into the VC++ debugger from VB, but I can't really remember how. But
_asm int 3
will work in VC++ to kick you into the debugger. You need to compile in debug mode to do this. The problem is that once you stop the debugger, VB will close (if you ran your app from within), so make sure you saved everything and have a link to start it again at hand. It can get VERY annoying.

[ejudy]

Thank you for your help!

Cornedbee, I 'll have a try.