Re: pointers problem

[Lee <t.lee.davidson@xxxxxxxxx>]

On 10/16/26 1:26 PM, valaquarus wrote:
> Dear Lee,
> I did what you suggest, changing  QRcode_encodeString external function to return a QRcode structure, I can confirm it works 
> fine but I don't know how to free the pointer and the program tells it to me : free()  invalid pointer at closing.

You would also need to change the QRcode_free to accept a QRcode structure:
Private Extern QRcode_free(qrcode As QRcode)

and change where it is freed to:
QRcode_free(stQr)

I have attached my modified MQRCode.module. But, again I stress that your version and mine both work on my system and do not 
cause a segmentation fault.


> I declare now Library "libqrencode:4.1.1" as my machine doesn't find 4.1.1-4.

The "-4" at the end of the version number is only a Manjaro package build number. That will not be found searching packages with 
pacman. I got that number using `pacman -Qi qrencode`.

You might want to leave the Library specification as: Library "libqrencode:4". Otherwise, if the library version changes, your 
program won't run even though the new version is quite likely fully compatible with your code. I mentioned the version number 
only for comparison between yours and mine.


> > the program displays an incorrect QR code according to one online generator
> How did you catch it?

I was mistaken. I tried one online QR code generator and it produced a different image than your program did. I have now tried 
three different online generators, and all three produced different images from each other. But, they all decode to the same 
text, as does yours.


> I made a break point and turn around step by step, I have a segmentation where it wants and when it wants , not in one place and 
> not only one place.

I would put a break point on the two lines that call the external functions. When the program stops, go ahead and continue using 
the Run button. Perhaps then you can determine which one is the culprit.


--
Lee

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' Gambas module file

Library "libqrencode:4"

Public Struct QRcode
   iVersion As Integer  ' 4 x
   iWidth As Integer ' 4 x
   pData As Pointer
End Struct

Private Extern QRcode_encodeString(sText As String, iVersion As Integer, iLevel As Integer, iHint As Integer, iCasesensitive As Integer) As QRcode

Private Extern QRcode_free(qrcode As QRcode)


Public Function GenerateQR(sTextToEncode As String, iLargeur As Integer) As Image

   Dim stQr As QRcode
   Dim img As Image
   Dim iX, iY, iInd As Integer
   Dim ibByte As Byte
   Dim pixelSize As Float
   Dim targetSize As Integer = iLargeur

   If IsNull(sTextToEncode) = True Then
      Message.Error(("QR code generation stopped!"))
      Return Null
   Endif

   stQr = QRcode_encodeString(sTextToEncode, 0, 2, 2, 1)  ' iHint = 2 ou 3

   If stQr = Null Then
      Message.Error(("QR code generation failed!"))
      Return Null
   Endif

   pixelSize = targetSize / stQr.iWidth
   img = New Image(targetSize, targetSize, Color.White, Image.Standard)

   Paint.Begin(img)

   For iY = 0 To stQr.iWidth - 1
      For iX = 0 To stQr.iWidth - 1
         ibByte = Byte@(stQr.pData + iInd)

         If (ibByte And 1) Then
            Paint.Brush = Paint.Color(Color.Black)
            Paint.Rectangle(iX * pixelSize, iY * pixelSize, pixelSize, pixelSize)
            Paint.Fill
         End If

         Inc iInd
      Next
   Next

   Paint.End

   If Error Then
      Message.Error(Str(Error.Class) & ", code : " & Error.Code & ",  " & Str(Error.Backtrace) & " à " & Error.Where & "\n" & Error.Text)
   Endif

   QRcode_free(stQr)
   Return img

End Function