Run-Time Error 49: Bad Dll calling Convention

[PatVB]

I am trying to call in into a c++ dll:

GetLibInfo(LPCTSTR libName, long* numEntries, long* numPoints, HANDLE* hLibComment, double* firstX, double* lastX, DATAXTYPE* pxtype, DATAYTYPE* pytype, long* bBaseline, long* libIsATR, long* bReadonly, LIBBYTES* libBytes)

From the vb module, I did this:

Public Declare Function GetLibInfo Lib "DLSLibSearch_ur.dll" (ByVal LibName As String, ByRef numEntries As Integer, ByRef numPoints As Integer, ByRef hlibComment As Integer, ByRef FirstX As Double, ByRef LastX As Double, ByRef DataXtype As Integer, ByRef DataYtype As Integer, ByRef bBaseline As Integer, ByRef libIsAtr As Integer, ByRef bReadonly As Integer, ByRef LibBytes As Integer) As Long

And when I call the function in a form, i get the error message

Private Function getInfo(ByVal LibName As String) As Long
    Dim numEntries As Integer
    Dim numPoints As Integer
    Dim hlibComment As Integer
    Dim FirstX As Double
    Dim LastX As Double
    Dim DataXtype As Integer
    Dim DataYtype As Integer
    Dim bBaseline As Integer
    Dim libIsAtr As Integer
    Dim bReadonly As Integer
    Dim LibBytes As Integer
    
    Dim ret As Long
    ret = GetLibInfo(LibName, numEntries, numPoints, hlibComment, FirstX, LastX, DataXtype, DataYtype, bBaseline, libIsAtr, bReadonly, LibBytes)
    
    geInfo = ret
End Function

I am quite sure it is a conversion that is killing me.......Any suggestions/ideas from anyone will do.

[dilettante]

Public Declare Function GetLibInfo CDecl Lib "DLSLibSearch_ur.dll" ...

... may work compiled to native code but almost certainly not when run in the IDE.

That C++ library was compiled using C-style calling conventions that are not compatible with Visual Basic, which assumes StdCall as used by most Win32 APIs. A custom typelib might also be a workaround for a calling convention mismatch.

[PatVB]

That did not solve it

[dilettante]

Well I didn't mean to imply it was a magic bullet. The CDecl keyword is ignored when you run the program within the IDE. It doesn't always work even when you compile to native code. It's also entirely undocumented, so you can't really expect much.

The real fix is to create a typelib to address the calling convention mismatch or else change the C++ library to use STDCALL and recompile it.