VB method not emitted because of invalid return type or parameter type

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I get the error: method 'PolCoefCalc' not emitted because of invalid return type or parameter type when I make a VB6 DLL and use the DLL in VC++.

Our VB6 source code is as following:

Dim xArray(60) as double
Dim YArray(60) as double
Public Function PolCoefCalc(ByRef pT() As Double, ByRef pU() As Double, ByRef pA() As Double) As Double
Dim resultA As Double
'1 pT=y copy this array elements to our internal array i.e. yArray
DataPoint = pN
'for insert data of 'pT' array from->to 'Yarray'
For i = 0 To DataPoint
Yarray(i) = pT(i)
Next i
'for insert data of 'pU' array from->to 'Xarray'
For i = 0 To DataPoint
Xarray(i) = pU(i)
Next i
'finally copy the result in pA array
For i = 1 To DataPoint
pA(i - 1) = xarray(i)
Next i
resultA = 0
PolCoefCalc = resultA
End Function

Kindly provide the solution and could you explain why VC++ does not show the 'PolCoefCalc' method and instead shows the error message.

Posted 18-May-10 1:56am

SanjayKothari

Updated 18-May-10 2:13am

Moak

v3

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Sauro Viti · Answer 1 · 2010-05-19T23:32:00

VB6 arrays are different from C/C++ arrays:

in VB an array of Double is treated as an object, they knows their size, and they are bounds checked

in C/C++ an array of double is just a memory area with the right size required to store as many numbers as declared, and accessed by pointer. The runtime does not keep trace of the array size, and it's responsibility of the programmer to avoid buffer overruns

When you use a VB6 dll from VC, Visual Studio will create a wrapper for that dll, but in your case it give you an error message because it is not able to create a C/C++ function equivalent to the VB6 one.